Preface - UFSCardq-gaia/images_2007/cookbook.pdf · Preface This manual contains procedures...

Preface

This manual contains procedures proposed in the literature for

microwave-assisted digestion of organic and inorganic samples. The

literature search was based on papers published in 2006 and 2007, because

previous years were covered in the first version of this manual [1].

Procedures employing microwave ovens designed for domestic use were

not included for safety reasons. On the other hand, digestion procedures

using flow-based systems were also not included because of the lack of

commercial equipments that would make them available for laboratories

performing routine analysis.

The compilation was focused on developed procedures using

commercial microwave ovens designed for laboratory applications. The

main focus was put on inorganic elemental analysis, but some extraction

procedures and procedures applicable for speciation analysis were also

included as important strategies that certainly will have a fast growing in

the coming years.

The compilation is not comprehensive, but reflects the experience of

the Group of Applied Instrumental Analysis (GAIA, Department of

Chemistry, Federal University of São Carlos, and Embrapa Cattle-

Southeast, São Carlos, SP, Brazil) and of the Group of Environmental

Analytical Chemistry (Department of Chemistry, Federal University of

Santa Maria, Santa Maria, RS, Brazil). However, it must be emphasized

that the listed procedures were not tested in the authors´ laboratories and

the authors cannot assume any responsibility about safety aspects.

ATTENTION: The experimental work with concentrated acids at high

pressures and temperatures is dangerous and may expose the analyst to

critical safety conditions.

The authors intend to follow this series of compilations about

microwave-assisted procedures with a publication titled Sample

Preparation Information Newsletter, but the periodicity of this publication

and its publication either in paper or in a digital medium is still being

discussed.

All work was made by the following members of both groups:

Group of Applied Instrumental Analysis (GAIA, UFSCAR, and Embrapa

Cattle-Southeast, SP, Brazil):

Adriana Alice de Oliveira, Allen Lopes de Barros, Amália Geiza Gama

Dionísio, Ana Rita de Araujo Nogueira, Carla Maira Bossu, Daniela

Schiavo, Edenir Rodrigues Pereira Filho, Eveline de Abreu Menezes,

Fernanda Santiago Chaves, Gilberto Batista de Souza, Joaquim de Araújo

Nóbrega, Juliana Aparecida Ferreira, Kelber dos Anjos de Miranda, Larissa

Macedo dos Santos, Marcos da Silva Gomes, Mário Henrique Gonzalez,

Rodolfo Carapelli, Silmara Rossana Bianchi, Silvéria Neves de Paula e

Souza, Simone Reder Matos Neves e Wladiana Oliveira Matos.

Group of Environmental Analytical Chemistry UFSM, Santa Maria, RS –

Brazil):

Cezar Augusto Bizzi, Érico Marlon de Moraes Flores, Fabiane

Goldschmidt Antes, Juliana Severo Fagundes Pereira e Paola de Azevedo

Mello

------------------------------------------------------------------------------------------

Reference

1. Grupo de Análise Instrumental Aplicada, Procedimentos – Preparo de

Amostras empregando Radiação Microondas, 2006. (CD-ROM)

Comparative studies of the sample decomposition of green and roasted

coffee for determination of nutrients and data exploratory analysis

Amorim Filho, V. R., Polito, W. L., Gomes Neto, J. A., Journal the

Brazilian Chemical Society, 18 (1), 47-53, 2007

Abstract

The contents of some nutrients in 35 Brazilian green and roasted coffee

samples were determined by flame atomic absorption spectrometry (Ca,

Mg, Fe, Cu, Mn, and Zn), flame atomic emission photometry (Na and K)

and Kjeldahl (N) after preparing the samples by wet digestion procedures

using i) a digester heating block and ii) a conventional microwave oven

system with pressure and temperature control. The accuracy of the

procedures was checked using three standard reference materials (National

Institute of Standards and Technology, SRM 1573a Tomato Leaves, SRM

1547 Peach Leaves, SRM 1570a Trace Elements in Spinach). Analysis of

data after application of t-test showed that results obtained by microwave-

assisted digestion were more accurate than those obtained by block digester

at 95% confidence level. Additionally to better accuracy, other favorable

characteristics found were lower analytical blanks, lower reagent

consumption, and shorter digestion time. Exploratory analysis of results

using Principal Component Analysis (PCA) and Hierarchical Cluster

Analysis (HCA) showed that Na, K, Ca, Cu, Mg, and Fe were the principal

elements to discriminate between green and roasted coffee samples.

Type of sample: green and roasted coffee

Sample amount: 0.400 g

Microwave oven (model): Perkin-Elmer-Anton Paar Multiwave (Graz,

Austria).

Vessel material: TFM (Teflon Fluor Modified)

Heating: Dig. A. Step 1: ramp time 3 min, initial power (100 W) and final

power (800 W). Step 2: 5 min, initial power (800 W) and final power (800

W). Step 3: ramp time 2 min, initial power (1000 W) and final power (1000

W). Step 4: 8 min, initial power (0 W) and final power (0 W).

Number of samples simultaneously digested: 8

Reagents: 6.0 mL concentrated HNO3 + 0.5 mL H2O2

Pretreatment general aspects: A mass of green coffee was added to the

polycarbonate container until approximately half of its total volume with

the magnetic bar, which tightly closed, was adapted to the support and

immersed in liquid nitrogen. Samples were pulverized by the impact

between coffee beans and the magnetic bar submitted to an oscillating

magnetic field of 20 impacts s-1. The cryogenic mill program consisted of

2 steps: 5 min of pre-cool and 2 min of mill. One of the selected samples

(sample number identification 1) was also ground using a Tecnal TE-648

Willye-type mill (Piracicaba, Brazil) without a previous sample freezing in

order to verify eventual contamination by mill components. This sample

was identified as number 2. Samples were oven-dried at 60 oC for 12 h.

Detection technique: flame atomic absorption spectrometry, flame atomic

emission spectrometry and Kjeldahl

Analytes: Ca, Fe, K, Mg, Cu, Mn, Na and Zn

Direct determination of arsenic in beer by electrothermal atomic

absorption spectrometry with deuterium background correction

(D2-ET-AAS)

Husakova, L., Cernohorsky, T., Sramkova, J. and Vavrusova, L., Food

Chemistry, 105 (1), 286-292, 2007

Abstract

We describe here a method for the direct determination of As in beer by

D2-ET-AAS, using Pd modifier, the atomization from platform and

insertion of a cooling step before atomization. This method results in a 40%

increase of sensitivity in peak-height measurements. Pd was found to be the

most advantageous chemical modifier for the elimination of phosphate

interference compared to Ni or Pt + citric acid. In addition, Pd is able to

stabilize As at charring temperatures of 1500 oC and further addition of V,

Mg or Sr have no influence. Addition of the modifier to standards and

samples made possible the use of matrix-free standard solutions for

attaining accurate analysis of diluted samples. The accuracy was checked

by the comparison of results of direct analysis of beer samples by the

proposed method with those found for microwave-digested samples

measured by an inductively coupled plasma orthogonal acceleration time-

of-flight mass spectrometer (ICP-TOFMS) method. The accuracy was also

confirmed by the analysis of certified reference samples.

Type of sample: beer

Sample amount: 5.0 mL

Microwave oven (model): Microwave system Speedwave TM MWS-3+.

The maximum total output of the microwave generator is 1450 W.

Vessel material: PTFE

Heating: Step 1: 5 min at 150 oC and 50% power. Step 2: 5 min at 220 oC

and 70% power. Step 3: 5 min at 100 oC and 10% power.

Number of samples simultaneously digested: not informed

Reagents: 6 mL of HNO3 (65% v/v)

Pretreatment general aspects: -

Detection technique: ICP-TOFMS

Analytes: As

Effect of four bentonite samples on the rare earth element

concentrations of selected Hungarian wine samples

Tatár, E., Mihucz, V. G., Virág, I., Rácz, L. and Záray, G., Microchemical

Journal, 85 (1), 132–135, 2007

Abstract

Rare earth elements (REEs) were detected and determined (except Eu, and

in some cases Gd, Tb and Tm) in three Hungarian wine samples –

Királyleányka, Blauer Portugieser and Merlot (2004 vintage) – from the

Eger viticulture area by double focusing inductively coupled plasma sector

field mass spectrometry (ICP-SF-MS) in low resolution mode (R=300).

The REE average concentrations of the samples determined after

microwave-assisted digestion were in the pg/cm−3 concentration range.

According to the results, among these grapes grown on volcanic slopes, the

REEs uptake by the Királyleányka and Blauer Portugieser seemed to be

more inhibited. Four, commercially available bentonite samples – fibrous

(Gelbenton), protein containing (Evergel), and two Na bentonites (BW200

and Tükrös) – were used for wine clarifying. Gelbenton altered the less the

REE concentrations of the wine samples. The lowest increase (1.1–1.5

times) was established for the Merlot red wine sample.

Type of sample: wine

Sample amount: 2 mL

Microwave oven (model): Multiwave Paar Physica device (Paar, Austria).

Vessel material: quartz

Heating: 40 min at 1000 W (nominal power value per six bombs) achieved

with a ramp of 50 W/min.


Reagents: 2 mL HNO3 65% (v/v)

Pretreatment general aspects: Samples were filtered through Millex

PDVF filters of 0.2 μm pore size

Detection technique: ICP-SF-MS

Analytes: Rare earth elements (REEs)

Influence of different bentonites on the rare earth element

concentrations of clarified Romanian wines

Mihucz, V. G., Done, C. J., Tatár, E., Virág, I., Záray, G. and Baiulescu, E.

G., Talanta, 70 (5), 984-990, 2006

Abstract

The rare earth element (REE) concentrations of 19 Romanian young wine

samples originating from the Dealurile Moldovei viticulture area were

determined by double focusing inductively coupled plasma mass

spectrometry (DF-ICP-MS) after microwave-assisted digestion with nitric

acid. The determination of Eu was hampered by the BaO molecular

interference. Generally, the red wine samples were more concentrated for

REEs than the white wine samples studied. The REE concentrations of the

four bentonites (Gelbenton, Evergel, BW200, Tükrös) determined after

their fusion were higher by three orders of magnitude than those of the

wine samples. After a simulated wine purification process performed with

these bentonite samples and a red and white pool samples, the REE

concentrations of the clarified wine samples increased by 1.2–1.5 times for

red, and 1.3–3 times for white wines in case of the fibrous bentonite sample

(Gelbenton), by about 2–5 times in case of the bentonite containing

ovalbumin, caseine and gelatine (Evergel), meanwhile this factor was about

20–25 for Na bentonite powder samples (BW200, Tükrös). On basis of the

chemometric evaluation using the REE concentrations as input data, the

majority of the Feteasca wines belonged to the same cluster as well as the

two Cabernet Sauvignon to another subcluster. The adequate choice of the

bentonite may allow the use of REEs as fingerprints for determining the

wine provenance.

Type of sample: white and read wine samples

Sample amount: 2 mL

Microwave oven (model): Multiwave Paar Physica (Anton Paar, Austria)


Heating: 40 min at 1000 W achieved with a ramp of 50 W/min.


Reagents: 2 mL of HNO3 65% (v/v)

Pretreatment general aspects: 2 mL of samples were previously filtered

through Millex PDVF filters of 0.2 μm.

Detection technique: double focusing ICP-MS.

Analytes: rare earth elements

Arsenic in marine tissue – The chalenging problems to electrothermal

and hydride generation atomic absorption spectrometry

Karadjova, I. B., Petrov, P. K., Serafimovski, I., Stafilov, T. and Tsalev, D.

L., Spectrochimica Acta Part B, 62 (3), 258-268, 2007

Abstract

Analytical problems in determination of arsenic in marine tissues are

addressed. Procedures for the determination of total As in solubilized or

extracted tissues with tetramethylammonium hydroxide and methanol have

been elaborated. Several typical lyophilized tissues were used: NIST SRM

1566a ‘Oyster Tissue’, BCR-60 CRM ‘Trace Elements in an Aquatic Plant

Lagarosiphon major)’, BCR-627 ‘Forms of As in Tuna Fish Tissue’,

IAEA- 140/TM ‘Sea Plant Homogenate’, NRCC DOLT-1 ‘Dogfish Liver’

and two representatives of the Black Sea biota, Mediterranean mussel

(Mytilus galloprovincialis) and Brown algae (Cystoseira barbata). Tissues

(nominal 0.3 g) were extracted in tetramethylammonium hydroxide

(TMAH) 1 mL of 25% m/v TMAH and 2 mL of water) or 5 mL of aqueous

80% (v/v) methanol (MeOH) in closed vessels in a microwave oven at

50 °C for 30 min. Arsenic in solubilized or extracted tissues was

determined by electrothermal atomic absorption spectrometry (ETAAS)

after appropriate dilution (nominally to 25 mL, with further dilution as

required) under optimal instrumental parameters (pyrolysis temperature

900 °C and atomization temperature 2100 °C) with 1.5 μg Pd asmodifier on

Zr–Ir treated platform. Platforms have been pre-treated with

2.7 μmol of zirconium and then with 0.10 μmol of iridium which served as

a permanent chemical modifier in direct ETAAS measurements and as an

efficient hydride sequestration medium in flow injection hydride generation

(FI-HG)–ETAAS. TMAH and methanol extract 96–108% and 51–100% of

As from CRMs. Various calibration approaches have been considered and

critically evaluated. The effect of species-dependent slope of calibration

graph or standard additions plot for total As determination in a sample

comprising of several individual As species with different ETAAS

behavior has been considered as a kind of ‘intrinsic element speciation

interference’ that cannot be completely overcome by standard additions

technique. Calibration by means of CRMs has given only semi-quantitative

results. The limits of detection (3σ) were in the range 0.5–1.2 mg/kg As

dry weight (wt.) for direct ETAAS analysis of extracts in both TMAH and

MeOH. Within-run precision (RSD, %) was 5–15% and 7–20 % for TMAH

and MeOH extracts at As levels 4–50 mg/kg dry wt., respectively. The

hydride active fraction of As species in extracts, i.e. the sum of

oxicologically-relevant arsenic species (inorganic As(III), inorganic As

(V), monomethylarsonate (MMA) and imethylarsinate (DMA) was

determined by FI-HG–ETAAS in diluted tissue extracts. Arsine,

monomethylarsine and dimethylarsine were generated from diluted TMAH

and MeOH extracts in the presence of 0.06–0.09 mol/L hydrochloric acid

and 0.075 mol/L L-cysteine. Collection, pyrolysis and atomization

temperatures were 450, 500, 2100 and 2150 °C, respectively. The LODs for

the determination of hydride forming fraction arsenite + arsenate + MMA +

DMA) in TMAH and MeOH extracts were in the range 0.003–0.02 mg/kg

As dry wt. Within-run precision (RSD, %) was 3–12% and 3–7% for MAH

and methanol extracts at As levels 0.15–2.4 mg/kg dry wt., respectively.

Results for the hydride forming fraction of As in TMAH and MeOH extract

as % from the certified value for total As (for CRMs) or vs. the total As in

TMAH extract (for real marine samples) are generally in agreement.

Type of sample: marine tissue


Microwave oven (model): Model MARS 5 (CEM Corporation, Matthews,

NC, USA)

Vessel material: Plastic CEM extraction vessel

Heating: Procedure A: 50 ºC (10min ramp time- 20 min hold time);

Procedure B: 50º C (10 min ramp time- 10 min hold time)


Reagents: Procedure A: Extraction 1: 1 mL of aqueous 25% (m/v) solution

of tetramethylammonium hydroxide (TMAH); Extraction 2: 5 mL of 80%

(v/v) methanol. Procedure B: 0.3 mL of aqueous 25% (m/v) solution of

TMAH.

Pretreatment general aspects: Samples were left for 30 min, capped and

placed in the rotor of MW extraction module

Detection technique: ETAAS and FI-HG-ETAAS

Analytes: As

Comparison of laser ablation, electrothermal vaporization and solution

nebulization for the determination of radionuclides in liquid samples

by inductively coupled plasma mass spectrometry

Grinberg, P., Yang, L., Mester, Z., Willie, S. and Sturgeon, R.E., Journal of

Analytical Atomic Spectrometry, 21 (11), 1202 - 1208, 2006

Abstract

The performance of solution nebulization (SN), electrothermal vaporization

(ETV) and laser ablation (LA) of dried micro-droplets as sample

introduction systems for ICP-MS are compared for the determination of

several radionuclides in digested biological tissue, nearshore sea-water and

river water. Samples were subjected to a Ca3(PO4)2 co-precipitation

preconcentration prior to analysis. Each introduction system possesses

unique advantages and disadvantages. ETV accommodates samples having

higher dissolved solids content; consequently, for SN and LA, sample

concentrates require additional dilution by 50- and 10-fold, respectively.

ETV and LA achieved similar sensitivities and limits of detection, the latter

ranging from 0.017 to 0.029 pg/ml. Although SN provides the best

precision (2% RSD versus 7 and 8% for ETV and LA, respectively),

formation of uranium hydride can be reduced at least 100-fold using LA of

dried micro-droplets of samples. The accuracy of the method was validated

by determination of U and Th in NIST SRM 1566b Oyster Tissue, NRC

CRM CASS-4 Nearshore Seawater and SLRS-4 Riverine Water and via

spike recoveries for Pu.

Type of sample: tissue


Microwave oven (model): MDS 2100 (CEM Corporation, Matthews, NC,

USA)

Vessel material: Teflon

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Heating: pressure of 8.16 atm for 30 min. After cooling, 200 µL of H2O2

(30%) was added, the vessels were recapped and heated again using the

same microwave program.


Reagents: 7 mL HNO3 conc. + 200 µL H2O2 30% (v/v)


Detection technique: ICP-MS

Analytes: Th, U and Pu

Determination of arsenic species in marine samples by HPLC-ICP-MS

Hirata, S., Toshimitsu, H. and Aihara, M., Analytical Sciences, 22 (1), 39-

43, 2006

Abstract

Arsenic speciation analysis in marine samples was performed using high

performance liquid chromatography (HPLC) with ICP-MS detection. The

separation of eigth arsenic species viz. arsenite (AsIII), monomethylarsonic

acid (MMA), dimethylarsinic acid (DMA), arsenate (AsV), arsenobetaine,

trimethylarsine oxide (TMAO), arsenocholine and tetramethylarsonium ion

(TeMAs) was achived on a Shiseido Capcell Pak C18 column by using an

isocratic eluent (pH 3.0), in wich condition AIII and MMA were co-eluted.

The entire separation was accoplished in 15 min. The detection limits for 8

arsenic species by HPLC/ICP-MS were in range of 0.02 – 0.10 μg L-1

based on 3δ of blank response (n = 9). The precision was calculated to be

3.1 – 7.3% (RSD) for all eight species. The method them succesfully

applied to several marine samples e.g., oyster, scallop, fish, and shrimps.

For the extraction of arsenic species from seafood products, the low power

of microwave digestion was employed. The extraction efficiency was in the

range of 52.9 – 112.3%. Total arsenic concentrations were analyzed by

using the microwave acid digestion. The total arsenics in the certified

reference materials (DORM-2 and TORT-2) were analyzed and agreed

with the certified values. The concentrations of arsenics in marine samples

were in the range 6.6 – 35.1 μg/g.

Type of sample: oyster, scallop, fish and shrimps


Microwave oven (model): MCS 950 (Prolabo, France)


Heating: 10 min at 50 W


Reagents: 10 mL H2O

Pretreatment general aspects: the samples were dried previously the

microwave extraction procedure.

Detection technique: HPLC/ICP-MS

Analytes: arsenite (AsIII), monomethylarsonic acid (MMA),

dimethylarsinic acid (DMA), arsenate (AsV), arsenobetaine, trimethylarsine

oxide (TMAO), arsenocholine and tetramethylarsonium ion (TeMAs).

Determination of 30 elements in colorectal biopsies by sector field

inductively coupled plasma mass spectrometry: method development

and preliminary baseline levels

Bocca, B., Lamazza, A., Pino, A., Masi, E., Iacomino, M., Mattei, D.,

Rahimi, S., Fiori, E., Schillaci, A., Alimonti, A. and Forte, G. Rapid

Communications in mass spectrometry, 21 (11), 1176-1782, 2007

Abstract

An analytical procedure applicable to restricted sample sizes was

developed and applied to the analysis of 30 chemical elements in colorectal

biopsies of healthy patients. Acidic microwave digestion processed ≤ 10mg

of tissue at 80 oC in 15 mL polystyrene liners. The digests were diluted to a

volume of 2 mL with high-purity water and directly analyzed by sector

field inductively coupled plasma mass spectrometry without further

specimen handling. A careful selection of isotopes and instrumental

resolution permitted the quantification in a single analytical sequence both

of the elements present at parts per trillion and of those at parts per million.

The accuracy calculated on BCR 184 ranged from 93.3–110%, the

recoveries of the biopsy material was in the range 95.2–105%, the precision

was < 10%, and the blank levels were much below those expected in

biopsy samples. The metal concentrations (on a dry-weight basis) in

colorectal normal tissue showed a large range of variation: Ag, Au, Be, Bi,

Co, Li, Sb, Tl, V,Wand Zr were below 50 ng/g; As, Ba, Cd, Cr, Cs, Hg,

Mo, Ni, Pb, Se and Sn were distributed from 100 to 500 ng/g; Al, Cu, Fe,

Mn, Sr and Zn were from a few mg/g to 100 mg/g; and Ca and Mg were at

a level of 1000 mg/g. These data represent the first attempt to achieve an

elemental profile in the colorectal mucosa of healthy patients as baseline

level measurements for studies focused on the imbalance of chemical

elements in diseased mucosa.

Type of sample: colorectal biopsies

Sample amount: 0.002-0.010 g

Microwave oven (model): Milestone Ethos 900-Mega II oven (FKV,

Milestone, Bergamo, Italy) loading a MultiPREP 80 rotor (FKV Milestone)

Vessel material: not informed

Heating: temperature ramp from 25 to 808 oC, for a total digestion time of

about 2 h

Number of samples simultaneously digested: capacity of 79 liners plus

Reagents: 0.5 mL of ultrapure HNO3

Pretreatment general aspects: The tissues were dried at 105 oC overnight,

with water content ranging between 59 and 84%

Detection technique: SF-ICP-MS

Analytes: Ag, As, Au, Be, Bi, Co, Li, Sb, Tl, V, Zr, Ba, Cd, Cr, Cs, Hg,

Mo, Ni, Pb, Se, Sn, Al, Cu, Fe, Mn, Sr and Zn

Determination of Hg and Se in biological materials by chemical vapor

generation electrothermal vaporization inductively coupled plasma

mass spectrometry using isotope dilution calibration after microwave-

assisted digestion with aqua regia

Vieira, M. A., Ribeiro, A. S., Dias, L. F. and Curtius, A. J., Journal of

Brazilian Chemical Society, 17 (5), 923-928, 2006

Abstract

A method for the determination of Hg and Se in biological materials by

chemical vapor generation electrothermal vaporization inductively coupled

plasma mass spectrometry (CVG-ETV-ICP-MS) using isotope dilution

calibration after acid digestion is proposed. The samples were digested with

aqua regia in a microwave oven. The isotope ratios used for quantification

were: 201Hg/202Hg and 77Se/82Se. A NaBH4 solution stabilized with NaOH

was used as reducing agent. The retention and vaporization temperatures in

the graphite tube were 150 and 2000 ºC, respectively. Six certified

biological materials were analyzed and the obtained concentrations were in

good agreement with the certified values according to the t-test for a

confidence level of 95%. The detection limits in the sample were 0.7 and

3 ng/g, for Hg and Se respectively. The method is precise, accurate and

adequate for the analysis of biological samples in routine and demonstrates

the feasibility of using isotope dilution for the proposed system.

Type of sample: biological materials (human hair, lyophilized pig kidney,

dogfish liver, dogfish muscle and lobster hepatopancreas)


Microwave oven (model): Ethos Plus (Milestone Corporation, Sorisole,

Italy)


Heating: 5 steps microwave oven temperature program was adopted

2 min at 50 °C and 400 W maximum power; 2 min at 50 °C and 200 W

maximum power; 6 min at 80 °C and 550 W maximum power; 5 min at

80 °C and 1000 W maximum power; 7 min at 160 °C and 1000 W

maximum power


Reagents: 3.5 mL of aqua regia + 1 mL of deionized water


Detection technique: CVG-ETV-ICP-MS

Analytes: Hg and Se

Determination of soluble toxic arsenic species in alga samples by

microwave-assisted extraction and high performance liquid

chromatography–hydride generation–inductively coupled plasma-

atomic emission spectrometry

Salgado, S. G., Nieto, M. A. Q. and Simón, M. M. B., Journal of

Chromatography A, 1129 (1), 54-60, 2006

Abstract

A microwave-based procedure for arsenic species extraction in alga

samples (Sargassum fulvellum, Chlorella vulgaris, Hizikia fusiformis and

Laminaria digitata) is described. Extraction time and temperature were

tested in order to evaluate the extraction efficiency of the process. Arsenic

compounds were extracted in 8ml of deionised water at 90 ºC for 5 min.

The process was repeated three times. Soluble arsenic compounds extracted

accounted for about 78–98% of total arsenic. The results were compared

with those obtained in a previous work, where the extraction process was

carried out by ultrasonic focussed probe for 30 s. Speciation studies were

carried out by high performance liquid chromatography–hydride

generation–inductively coupled plasma-atomic emission spectrometry

(HPLC-HG-ICP-AES). The chromatographic method allowed us to

separate As(III), As(V), monomethylarsonic acid and dimethylarsinic acid

in less than 13 min. The chromatographic analysis of the samples allowed

us to identify and quantify As(V) in Hizikia sample and Sargasso material,

while the four arsenic species studied were found in Chlorella sample. In

the case of Laminaria sample, none of these species was identified by

HPLC-HG-ICP-AES. However, in the chromatographic analysis of this

alga by HPLC-ICP-AES, an unknown arsenic species was detected.

Type of sample: alga (Sargassum fulvellum, Chlorella vulgaris, Hizikia

fusiformis and Laminaria digitata)

Sample amount: 0.2 g for extraction and 0.25 g for digestion

Microwave oven (model): MARS 5 Microwave oven (CEM Corporation,

Matthews, NC, USA)

Vessel material: Teflon and Pyrex

Heating: 90 ºC was applied for 5 min for extraction procedure and 30 min

at 15.30 atm and 210 ºC for digestion procedure.


Reagents: 8 mL of deionised water for extraction procedure and 10 mL of

HNO3 conc. for digestion procedure.

Pretreatment general aspects: Hijiki algawas triturated in a mill to a

particle size of 125 μm and Laminaria capsules were opened and placed in

a polyethylene bottle before the analytical treatment.

Detection technique: HPLC-HG-ICP-AES

Analytes: arsenic species

Digestion of biological materials using the microwave-assisted sample

combustion technique

Mesko, M. F., Moraes, D. P., Barin, J. S., Dressler, V. L., Knapp, G. and

Flores, E. M. M., Microchemical Journal, 82 (2), 183-18, 2006

Abstract

In this study a procedure for sample digestion based on sample combustion

assisted by microwave radiation is proposed. Combustion is started by

microwave radiation in the presence of oxygen under pressure using

ammonium nitrate as aid for ignition. The system was adapted in a

microwave oven with quartz closed vessels. A quartz piece is used

simultaneously as a sample holder and as protection to the cap of quartz

vessel from the flame generated in the combustion process. Sample was

pressed into a pellet and placed on a disc paper in the holder and 50 μL of

50% m/v ammonium nitrate solution was added. The influence of the

absorption solution (diluted and concentrated nitric acid or water) on the

recoveries for Cu and Zn was evaluated. About 3 s of microwave

irradiation was necessary to start the combustion. The combustion process

was evaluated in relation to the influence of sample mass on the ignition

time, combustion time and maximum operation pressure. Bovine liver,

milk powder and oyster tissue certified reference materials were used to

evaluate the accuracy of the procedure for determination of copper and

zinc. Good agreement for zinc (96% to 103%) was obtained from bovine

liver certified reference material when microwave combustion and

microwave combustion followed by reflux were used to sample

decomposition, even if water was used for absorption of analyte. For

copper, the combustion followed by reflux of 5 min allows an agreement

from 96% to 100%. Similar results were obtained for oyster tissue samples.

However, for milk powder good agreement close to 100% was obtained

only if 4 mol/L HNO3 was used with a reflux step. Results from the


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proposed procedure were also compared to those from conventionally used

procedures for biological samples decomposition, such as wet digestion in

open vessels and microwave-assisted digestion in closed vessels. The

advantages of this procedure include the complete sample decomposition in

less time than other procedures and the acid consumption was always lower

than 2%. Another advantage is the low residual carbon content, less of

1.4% without reflux and less than 0.3% with the reflux step and the

possibility of use of diluted acid as absorbing solution. Moreover, the new

holder allows an effective protection of the vessel cap to burnt high masses.

Type of sample: Bovine liver, milk powder and oyster tissue certified

reference materials


Microwave oven (model): Multiwave 3000 (Anton Paar)

Vessel material: Quartz

Heating: The microwave irradiation program used for the combustion

procedure was as follows: 1) 1400 W for 60 s, 2) 1400 W for 5 min

(optional step for reflux), and 3) 0 W for 20 min for cooling if step 2 was

applied. During steps 1 and 2, the cooling fan was selected at level 2 (level

3 was applied only for cooling).


Reagents: 6 mL HNO3

Pretreatment general aspects: samples between 50 and 500 mg were

pressed and weighed directly on the filter paper.

Detection technique: FAAS

Analytes: Cu and Zn

Element fingerprinting of marine organisms by dynamic reaction cell

inductively coupled plasma mass spectrometry

Cubadda, F., Raggi, A. and Coni, E., Analytical and Bionalytical

Chemistry, 384 (4), 887-896, 2006

Abstract

A method for the determination of sixteen elements (Al, As, Cd, Co, Cr,

Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Sn, V, Zn) in seafood by dynamic reaction

cell inductively coupled plasma mass spectrometry (ICP–DRC–MS) is

presented. A preliminary study of polyatomic interferences was carried out

in relation to the chemical composition of marine organisms belonging to

different taxa. Acid effects and other matrix effects in marine organisms

submitted to closed-vessel microwave digestion were investigated as well.

Ammonia was the reactive gas used in the DRC to remove polyatomic ions

interfering with 27Al, 52Cr, 56Fe and 51V. Optimal conditions for the

simultaneous determination of analytes were identified in order to develop

a fast multielement method. A suite of real samples (mussels and various

fish species) were used during method development along with three

certified reference materials: BCR CRM 278R (mussel tissue), BCR CRM

422 (cod muscle) and DORM-2 (dogfish muscle). The proposed analytical

approach can be used in conjunction with suitable chemometric procedures

to address quality and safety issues in aquaculture and fisheries. As an

example, a case study is described in which mussels from three farming

sites in the Venice Lagoon were distinguished by multivariate analysis of

element fingerprints.

Type of sample: Biological


Microwave oven (model): Ethos Pro microwave labstation (Milestone

Corporation, Sorisole, Italy)


Heating: Temperature control during microwave irradiation allowed

automatic continuous adjustment of power output and the accomplishment

of the following temperature profile: 5 min ramp to 120 °C, 5 min at

120 °C, 5 min ramp to 190 °C, 15 min at 190 °C. The digested samples

were kept refrigerated at 4 °C.


Reagents: 5 mL HNO3 + 2 mL H2O2 + 1 mL H2O (sample), and 3 mL

HNO3 + 1.5 mL H2O2 + 3.5 mL H2O (certified reference materials)



Analytes: Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Se, Sn, V and

Zn

Evaluation of toxic metals in biological samples (scalp hair, blood and

urine) of steel mill workers by electrothermal atomic absorption

spectrometry

Afridi, H. I., Kazi, T. G., Jamali, M. K., Kazi, G. H., Arain, M. B., Jalbani,

N., Shar, G. Q. and Sarfaraz, R. A., Toxicology and Industrial Health, 22

(9), 381-393, 2006

Abstract

The determination of toxic metals in the biological samples of human

beings is an important clinical screening procedure. This study aimed to

assess the possible influence of environmental exposure on production

workers (PW) and quality control workers (QCW) of a steel mill, all male

subjects aged 25-55 years. In this investigation, the concentrations of Pb,

Cd, Ni and Cr were determined in biological samples (blood, urine and

scalp hair samples) from these steel mill workers in relation to controlled

unexposed healthy subjects of the same age group. After pre-treatment with

nitric acid-hydrogen peroxide, the samples were digested via a microwave

oven, and for comparison purposes, the same samples were digested by the

conventional wet acid digestion method. The samples digested were

subjected to graphite furnace atomic absorption spectrometry (GF AAS).

To assess the reliability of these methods, critical factors, such as detection

limit(s), calibration range(s), accuracy and precision, were studied. Quality

control for these procedures was established with certified sample of

human hair, urine and whole blood. The results indicate that the level of

lead, cadmium and nickel in scalp hair, blood and urine samples were

significantly higher in both groups of exposed workers (QW and PW) than

those of the controls. The possible connection of these elements with the

etiology of disease is discussed. The results also show the need for

immediate improvements in workplace ventilation and industrial hygiene

practices.

Type of sample: scalp hair, blood and urine

Sample amount: 0.2 g of scalp hair, 0.5 mL of blood and 1 mL of urine

Microwave oven (model): not informed

Vessel material: Teflon PFA

Heating: 250 W for 5 min for blood and urine, and 250 W for 15 min for

hair samples.


Reagents: 2 mL of concentrated HNO3 and 1 mL of H2O2 30% (v/v)


Detection technique: GF AAS

Analytes: Pb, Cd, Ni and Cr

Highly improved sensitivity of TS-FF-AAS for Cd(II) determination at

ng L-1 levels using a simple flow injection minicolumn

preconcentration system with multiwall carbon nanotubes

Tarley, C. R. T., Barbosa, A. F., Segatelli, M. G., Figueiredo, E. C. and

Luccas, P. O., Journal of Analytical Atomic Spectrometry, 21 (11), 1305-

1313, 2006

Abstract

A new method for cadmium determination at ng L-1 levels is described. The

method is based on the on-line coupling of a flow preconcentration system

using multiwall carbon nanotubes (MWCNT) as sorbent with TS-FF-AAS

determination. Cadmium preconcentration was at pH 4.9 onto an MWCNT

minicolumn (30 mg) for 2 min at a 5.0 mL min-1 flow rate. The elution step

is performed by using 0.5 mol/L HNO3 and the cadmium desorbed is

directly pumped to a TS-FF-AAS. All experimental parameters that play

important roles in system performance were evaluated and optimized by

means of fractional factorial designs and response surface methodology.

The excellent characteristics of MWCNT as sorbent, mainly owing to its

high surface area, make it possible to obtain a preconcentration factor of

51-fold, thus improving the detection and quantification limits in

TS-FF-AAS, 11.4 and 38.1 ng/L, respectively. When the flow

preconcentration system, FI-TS-FF-AAS, was compared with FAAS alone,

an increase in the sensitivity of 640-fold was obtained. The calibration

graph was linear with a correlation coefficient higher than 0.999 from 38.1

to 1250 ng/L. Repeatability of the measurements (n = 10), assessed as

relative standard deviation (RSD), was found to be 6.5 and 2.1% for

cadmium concentrations of 100 and 1000 ng L-1, respectively. Important

parameters to characterize the flow preconcentration system were also

evaluated, the consumption index being 0.196 mL, the concentration

efficiency 25.5 min-1 and the sample throughput 20 samples per hour. In

order to demonstrate the accuracy of the system, addition and recovery

studies in water samples (mineral water, tap water and river water) and

cigarette samples were carried out. Moreover, for the same purpose,

cadmium was determined in certified biological materials (Bovine Liver

and Rye Grass), giving an average result in close agreement with the

certified value.

Type of sample: Bovine Liver, Rye Grass and cigarette samples


Microwave oven (model): microwave oven Milestone Corporation,

Sorisole, Italy


Heating: samples were digested using two heating steps in a microwave

oven: 5 min at 400 W and 5 min at 700 W. After digestion, solutions were

heated on a hot plate to near dryness.

Number of samples simultaneously digested: two

Reagents: 10 mL HNO3 65% (v/v)+ 4 mL 30% (m/v) H2O2


Detection technique: TS-FF-AAS

Analytes: Cd

Manganese determination by GFAAS in feces and fish feed slurries

Loureiro, V. R., Saleh, M. A. D., Moraes, P. M., Neves, R. C. F., Silva, F.

A., Padilha, C. C. F., Padilha, P. M., Journal the Brazilian Chemical

Society, 18 (6), 1235-1241, 2007

Abstract

This paper presents a simple, fast and sensitive method to determine

manganese in samples of feces and fish feed by graphite furnace atomic

absorption spectrometry (GFAAS) by the direct introduction of slurries into

the graphite tube. The limits of detection (LOD) and quantification (LOQ)

calculated for 20 readings of the blank of the standard slurries (0.50% m/v

of feces or feed devoid of manganese) were 28 and 92 µg/kg for the

standard feces slurries and 34 and 110 µg/kg for the standard feed slurries.

The proposed method was applied in bioavailability studies of manganese

in different fish feeds and their results proved compatible with those

obtained for samples mineralized by acid digestion using microwave oven.

Type of sample: feces and fish feed


Microwave oven (model): Model DGT 100, Provecto Analítica, Brazil


Heating: Step 1: 300 W, 3 min. Step 2: 0 W, 2 min. Step 3: 450 W, 5 min.

Step 4: 550 W, 5 min. Step 5: 650 W, 5 min. Step 6 (ventilation): 0 W,

5 min.


Reagents: 2.5 mL HNO3 + 0.5 mL H2O2 30%

Pretreatment general aspects: The fish feces and feed samples were dried

at 50°C in an oven with forced air circulation for 48 h and then

cryogenically ground.

Detection technique: GFAAS

Analytes: Mn

Method for determination of selenium and arsenic in human urine by

atomic fluorescence spectrometry

Wieteha-Posłuszny, R., and Dobrowolska, J., Analytical Letters, 39 (15),

2787-2796, 2006

Abstract

The study presents the method for simultaneous determination of selenium

and arsenic in human urine by atomic fluorescence spectrometry (AFS).

According to the procedure developed, a sample is first digested in the

microwave system, then chemically treated in the flow through a hydride

generation system, and finally exposed to measurements in a double-

channel atomic fluorescence spectrometer. It has been revealed that

selenium and arsenic can be accurately determined with detection limit of

0.13 and 0.16 mg/L and repeatability (RSD) of 1.0 and 1.2%, respectively.

The urine samples taken from a control group and from persons subjected

to a special diet were analyzed. The obtained results proved that the method

developed was capable of controlling reliably even slight changes of both

elements in a wide range of their concentrations, and, as such, that it can be

recommended to be used for clinical and toxicological purposes.

Type of sample: human urine


Microwave oven (model): MARS 5 (CEM Corporation, Matthews, NC,

USA)


Heating: The digestion condition for the microwave system was applied as

8 min for 960 W, 8 min for 960 W, and 8 min for 1080 W. After digestion,

the sample solution was cooled in the air to 25 °C and then blown under

nitrogen flow for 10 min. At the end, a sample was transferred into a 25 mL

volumetric flask, dosed by 12.5 ml of 6 mol/L HCl, and diluted to the mark

with water.



Reagents: 7 mL HNO3


Detection technique: AFS

Analytes: As and Se

Monitoring trace elements in selected organs of Antarctic penguin

(Pygoscelis adeliae) by plasma-based techniques

Smichowski, P., Vodopivez, C., Muñoz-Olivas, R., and Gutierrez, A.M.,

Microchemical Journal , 82 (1) , 1-7, 2006

Abstract

A study was undertaken to evaluate the content and distribution of eight

key elements, namely, As, Cd, Co, Cu, Hg, Mn, Pb and Se in liver, kidney

and muscle of chick individuals of Adélie penguin (Pygoscelis adeliae).

Samples were collected during the 2002/2003 austral summer season

campaign around Jubany Station (Argentine scientific station), Potter Cove,

King George Island. Solutions of organs were prepared by acid-assisted

microwave (MW) digestion by employing HNO3 and H202. Instrumental

techniques selected to analyze the different tissues were inductively

coupled plasma optical emission spectroscopy (ICP OES) and inductively

coupled plasma mass spectrometry (ICP-MS). A wide range of elements

retention capacity among the different organs was observed and the ranges

ascertained are as follows (in µg/g): As, 0.5 (liver)–0.8 (muscle); Cd, <0.07

(muscle)–3.4 (kidney); Co, 0.07 (liver)–0.7 (muscle); Cu, 0.6 (muscle)–18

(liver); Hg, 0.2 (kidney)–2.7 (liver); Mn, 1.5 (muscle)–10 (liver); Pb, 0.1

(muscle)–2.0 (liver); Se, 3.0 (muscle)–8.4 (liver). The observed trend in

metal accumulation in the three organs of chick penguins was in the order

Cu>Mn>Se >>As>Co>Pb>>Cd>Hg. Levels of metals and metalloids were,

in general terms, higher in liver that is a specific target organ for metal

accumulation. This study aimed at contributing to the establishment of

base-line data on potential pollutants of ecotoxicological interest in the

Antarctic ecosystem.

Type of sample: liver, kidney and muscle of penguin



Microwave oven (model): CEM MSP-1000 (CEM Corporation,

Matthews, NC, USA)

Vessel material: Teflon-PFA

Heating: The MW program is: 1 min at 250 W, 1 min at 0 W, 5 min at 250

W, 5 min at 400 W and 5 min at 650 W. After cooling, a completely clear

and homogeneous digest was observed and it was diluted to 25 mL with

deionized water.

Number of samples simultaneously digested: two

Reagents: 4 mL HNO3 conc. + 2.5 mL H2O2 (m/v)

Pretreatment general aspects: Samples were defrosted in the laboratory,

dried at 50 -C until constant weight and stored in a dark place (at room

temperature) until their analysis. Samples were homogenized and ground to

a fine powder in a tungsten carbide mortar.

Detection technique: ICP OES and ICP-MS

Analytes: Pb, Mn, Se, Ar, Cd, Co, Cu and Hg

Multi-element determination in raft mussels by fast microwave-

assisted acid leaching and inductively coupled plasma-optical emission

spectrometry

Seco-Gesto, E. M., Moreda-Piñeiro, A., Bermejo-Barrera, A. and Bermejo-

Barrera, P., Talanta, 72 (3), 1178-1185, 2007

Abstract

Studies on the application of a short microwave irradiation cycle and the

use of diluted acids to extract trace elements from raft mussel samples were

developed. Multi-element determinations (Al, Ba, Cd, Cr, Cu, Fe, Mn, Pb,

Sn, V and Zn) were carried out by inductively coupled plasmaoptical

emission spectrometry (ICP-OES). Parameters such as acid/oxidizing

reagents (diluted nitric acid, hydrochloric acid and hydrogen peroxide)

concentrations, acid/oxidizing solution volume, temperature, ramp time and

hold time for the microwave heating were simultaneously studied by using

an experimental design approach. The optimum conditions have showed

the sample pre-treatment of 10 mussel samples to less than 3.0 min when a

microwave power of 600Wand a controlled temperature of 65 ◦C were

used. This time (hold time plus ramp time) is quite shorter than those

reported for conventional microwave-assisted acid digestion procedures.

Since temperature inside the reactor is not high, the venting time can be

shorted to 15 min. In addition, the concentration of acid/oxidizing reagents

needed to complete the acid leaching (2.5 M, 3.0 M and 0.5% (m/v) for

nitric acid, hydrochloric acid and hydrogen peroxide, respectively) is lower

than the required concentration for a conventional microwave-assisted acid

digestion (concentrated acids). The proposed method has showed a good

repeatability of the overall method, and relative standard deviations

between 11 and 2% were reached for 12 replicate microwave-assisted acid

leaching and ICP-OES measurements. The method was finally validated by

analyzing TORT-1 and GBW-08571 certified reference materials and it

was successfully applied to fast multi-element determinations in several

raft mussel samples.

Type of sample: Mussel (Mytilus galloprovincialis) soft tissue (muscle and

gill)


Microwave oven (model): Ethos Plus (Milestone, Sorisole, Italy)


Heating: Step 1: 65 ºC, 2.5 min. Step 2: 600 W, 65 ºC and 0.5 min


Reagents: 15 mL of oxidizing solution (2.5 mol/L, 3.0 mol/L and

0.5% (m/v) of HNO3, HCl e H2O2, respectively)

Pretreatment general aspects: Mechanical blending, homogenization and

freeze dry processes; samples were ground in a ball mill, mean particle size

50 µm.

Detection technique: ICP OES

Analytes: Al, Ba, Cd, Cr, Cu, Fe, Mn, Pb, Sn, V and Zn

Sample preparation for metalloprotein analysis: A case study using

horse chestnuts

Magalhães, C. S. and Arruda, M. A. Z., Talanta, 71 (5), 1958-1963, 2007

Abstract

In the present work, 11 different procedures for protein and metalloprotein

extraction from horse chestnuts (Aescullus hippocastanum L.) in natura

were tested. After each extraction, total protein was determined and, after

protein separation through sodium dodecyl sulphate-polyacrylamide gel

electrophoresis (SDS-PAGE), those metals belonging to the protein

structure were mapped by synchrotron radiation X-ray fluorescence

(SRXRF). After mapping the elements (Cr, Fe and Mn) in the protein

bands (ca. 33 and 23.7 kDa), their concentrations were determined using

atomic absorption spectrometry (ET AAS). Good results were obtained for

protein extraction using a combination of grinding and sonication.

However, this strategy was not suitable to preserve metal ions in the protein

structure. In fact, there was 42% decrease on Mn concentration using this

procedure, compared to that performed with sample agitation in water

(taken as reference). On the other hand, when grinding and agitation with

an extracting buffer was used, there was a 530% increase of Mn

concentration, when compared to the reference procedure. These results

indicate agreement between metal identification and determination in

proteins as well as the great influence of the extraction procedure (i.e., the

sample preparation step) for preserving metals in the protein structures.

Type of sample: gel protein band (horse chesnusts)


Microwave oven (model): Model DTG–100 Provecto, Brazil


Heating: Three steps: 1) 3 min at 400 W. 2) 6 min at 790 W. 3) 3 min at 0

W, the program being running twice. After finishing the sample

decomposition program, the Teflon vessels were placed on a hot plate

(60–70 oC) for evaporation the excess of HNO3.

Number of simultaneous treated samples: not informed

Reagents: 5 mL HNO3 + 1 mL H2O2

Pretreatment general aspects: 5mL of HNO3 and 1mL of H2O2: 30 min

for safety reasons

Detection technique: ETAAS

Analytes: Fe, Cr and Mn

Simultaneous determination of inorganic mercury, methylmercury,

and total mercury concentrations in cryogenic fresh-frozen and freeze-

dried biological reference materials

Point, D., Davis, W. C., Alonso, J. I. G., Monperrus, M., Christopher, S. J.,

Donard, O. F. X., Becker, P. R. and Wise, S. A., Analytical and

Bioanalytical Chemistry, 389 (3), 787-798, 2007

Abstract

Two speciated isotope dilution (SID) approaches consisting of a single-

spike (SS) method and a double-spike (DS) method including a

reaction/transformation model for the correction of inadvertent

transformations affecting mercury species were compared in terms of

accuracy, method performance, and robustness for the simultaneous

determination of methylmercury (MeHg), inorganic mercury (iHg), and

total mercury (HgT) concentrations in five biological Standard Reference

Materials (SRMs). The SRMs consisted of oyster and mussel tissue

materials displaying different mercury species concentration levels and

different textural/matrix properties including freeze-dried (FD) materials

(SRMs 1566b, 2976, and 2977) and cryogenically prepared and stored

fresh-frozen (FF) materials (SRMs 1974a, 1974b). Each sample was spiked

with (201)iHg (Oak Ridge National Laboratory, ORNL) and (MeHg)-Hg-

202 (Institute for Reference Materials and Measurements. IRMM-670)

solutions and analyzed using alkaline microwave digestion, ethylation, and

gas chromatography inductively coupled plasma mass spectrometry

(GC/ICP-MS). The results obtained by the SS-SID method suggested that

FF and FD materials are not always commutable for the simultaneous

determination of iHg, MeHg, and HgT, due to potential transformation

reactions resulting probably from the methodology and/or from the

textural/matrix properties of the materials. These transformations can

occasionally significantly affect mercury species concentration results

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obtained by SS-SID, depending on the species investigated and the

materials considered. The results obtained by the DS-SID method indicated

that the two classes of materials were commutable. The simultaneous and

corrected concentrations of iHg, MeHg, and HgT obtained by this

technique were not found to be statistically different form the certified and

reference concentration together with their expanded uncertainty budgets

for the five SRMs investigated, exemplifying the robustness, the accuracy,

and the improved commutability of this method compared to SS-SID

measurements.

Type of sample: oyster and mussel tissue reference materials


Microwave oven (model): CEM Corporation, Matthews, NC, USA


Heating: 30 W for 3.5 min


Reagents: 3 mL of Tetramethylammonium hydroxide 25% (v/v)


Detection technique: GC-ICP-MS

Analytes: inorganicHg, MeHg, and HgT

Validation of an inductively coupled plasma mass spectrometry

(ICP-MS) method for the determination of cerium, strontium, and

titanium in ceramic materials used in radiological dispersal devices

(RDDs)

Packer, A. P., Lariviere, D., Li, C., Chen, M., Fawcett, A., Nielsen, K.,

Mattson, K., Chatt, A., Scriver, C. and Erhardt, L. S., Analytica Chimica

Acta, 588 (2): 166-172, 2007

Abstract

In radiological dispersal device (RDD) studies, sintered ceramics made of

CeO2 and SrTiO3 were used to simulate actinide oxides and 90SrTiO3,

respectively. Instrumental neutron activation analysis (INAA), inductively

coupled plasma optical emission spectroscopy (ICP-OES), and inductively

coupled plasma mass spectrometry (ICP-MS) were investigated as possible

analytical techniques for the measurement of SrTiO3 and CeO2 constituents

in powder forms, sintered ceramics, and air particulates collected following

a detonation. For ICP-OES and ICP-MS analysis, new digestion procedures

were developed using a closed-vessel microwave apparatus. Acid mixtures

(HNO3:H2O2:HF (16:2:1) and HNO3:H2O2 (1:4)) were found to be effective

for the digestion of SrTiO3 and CeO2, respectively. The intercomparison

study confirmed that the results obtained by ICP-OES/MS are in good

agreement with INAA results. This also confirms the efficiency of the

digestion procedures for these refractory materials and the inter-

exchangeability of the instrumentation tested. Comparison between the

ICP-OES and the ICP-MS instrumentation for the determination of air

particulates shows, that although the two methods are equivalent, ICP-MS

provides better detection limits (0.11, 0.02, and 0.04 µg per filter for Ti, Sr,

and Ce, respectively) and the possibility to determine isotopic fractionation

as the result of an explosion.

Type of sample: powder and sintered SrTiO3, ceramic and CeO2 (powder,

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sintered, and air particulate)


Microwave oven (model): MARS 5 microwave oven by CEM (Matthews,

NC, USA)

Vessel material: Teflon high pressure (XP-1500 PlusTM)

Heating: powder and sintered SrTiO3 ceramic samples: 5 min at ramp

from 20 ◦C to 160 ◦C. 5min at hold a 160 ◦C. 5 min at ramp to 200 ◦C.

40 min at hold at 200 ◦C. For CeO2 samples (powder, sintered, and air

particulate samples): 5 min at ramp from 20 ◦C to 100 ◦C. 5 min at hold at

100 ◦C. 5 min at ramp to 160 ◦C. 20 min at hold at 160 ◦C.


Reagents: powder and sintered SrTiO3 ceramic samples: 10 mL of a

mixture of HNO3, H2O2, and HF (16:2:1). For CeO2 samples (powder,

sintered, and air particulate samples): 10 mL of a mixture of HNO3 and

H2O2 (1:4).


Detection technique: Instrumental neutron activation analysis (INAA),

ICP OES and ICP-MS

Analytes: Sr, Ti and Ce

Levels of nickel and other potentially allergenic metals in Ni-tested

commercial body creams.

Bocca, B., Forte, G., Petrucci, F. and Cristaudo, A., Journal of

Pharmaceutical and Biomedical Analysis, 44 (5), 1197–1202, 2007

Abstract

It is extensively well-known that Ni and other metals occurring as

impurities in cosmetic products might give rise to contact dermatitis in

subjects with pre-existing allergy. The present study on the content of 13

metals (Cd, Co, Cr, Cu, Hg, Ir, Mn, Ni, Pb, Pd, Pt, Rh, and V) in

moisturizing creams, labelled as “Ni-tested” (i.e., Ni content < 100 ng /g)

and available on the Italian market, provides a basis for assessing their

safety for consumers. Quantification of metals was performed by sector

field inductively coupled plasma mass spectrometry after microwave-

assisted acid digestion of products. The developed method had limits of

quantification less than 0.8 ng/g for all the elements; recovery was in the

interval 88% (Cd, Co) to 110 % (Hg), and precision was always under

7%. Nickel was present in all the products with levels between 17.5 and

153 ng/g; three skin creams were slightly above the concentration reported

on the label. The other elements were at levels below 1 µg/g. The highest

concentrations, in ng/g, of Co, Cr, Cu, and Mn were 222, 303, 51.2, and

59.9, respectively. Mean Cd, Pb, and V were below 5 ng/g, while Hg was

absent in all the samples. Among the new emergent allergens, Ir and Rh

were in traces or even undetectable, while Pt had levels of 2.65 and

6.28 ng/g in two creams and Pd was equal to 1.07 ng/g in one product. The

overall results are below the sensitizing limit proposed for consumer

products and, thus, probably have no significant toxicological effects.

Nevertheless, some creams presented amounts of Co and Cr comparable to

those of Ni and therefore they have to be monitored in consideration of

their cross-reactivity as well.

Type of sample: commercial body creams

Sample amount: Aliquots of 1 g

Microwave oven (model): Milestone Ethos 900-Mega II microwave oven

(FKV Milestone, Bergamo, Milan, Italy)

Vial material: PTFE

Heating: The cycle was as follows: 1) 10 min at 250 W. 2) 5 min at

400 W. 3) 5 min at 500 W. 4) 5 min at 600 W.


Reagents: 5 mL HNO3 + 1 mL HF


Detection technique: SF- ICP- MS

Analytes: Cd, Co, Cr, Cu, Hg, Ir, Mn, Ni, Pb, Pd, Pt, Rh, and V

Determination of arsenic in dolomites with a simple field spectrometric

device

Stec, K., Bobrowski, A., Kalcher, K., Moderegger, H. and Goessler, W.,

Microchimica Acta, 153 (1), 45-49, 2006

Abstract

A simple and an inexpensive procedure for the determination of total

arsenic in dolomites is proposed. The method applies the spectrometric

field device Supralab SD which was initially designed for the

determination of arsenic in drinking water. The method relies on the

formation of the volatile AsH3 and its reaction with mercuric bromide,

immobilized in a membrane, to yield a yellowish-brown reaction product,

which is spectrophotometrically detected. The dolomite samples were

rapidly dissolved in hot hydrochloric acid in an open vessel and then were

analyzed with the portable instrument. The 3 s detection limit of the

developed method was 0.1 μg/L as in the solution containing dissolved

dolomites. The time of As determination in the solution did not exceed

5 min. To validate the results obtained with the field device, hydrogen

generation inductively coupled plasma optical emission spectrometry

(HG-ICP-OES) and inductively coupled plasma mass spectrometry

(ICPMS) were used as reference methods using microwave-assisted

mineralization. Excellent agreement between the methods was obtained.

Type of sample: dolomite


Microwave oven (model): MLS-1200 Mega (Milestone Corporation,

Sorisole, Italy)


Heating: pressure and temperature were not informed, but the

decomposition time was 3 h.


Reagents: 5 mL HCl conc. + 1 mL HNO3 conc. for the As determination

by ICP OES and 5 mL HNO3 conc.

Pretreatment general aspects: The samples were washed and ground to a

grain size less than 63 mm prior to analysis.


Analytes: As

Determination of metals, metalloids and non-volatile ions in airborne

particulate matter by a new two-step sequential leaching procedure

Part A: Experimental design and optimisation

Canepari, S., Cardarelli, E., Giuliano, A. and Pietrodangelo, A. Talanta, 69

(3), 581-587, 2006

Abstract

The optimisation of a micro-analytical two-step sequential leaching

procedure for the determination of non-volatile ions (NO3−, SO4

2−, Cl−, Na+,

Mg2+, NH4+ and Ca2+) and of 17 elements (Al, As, Cd, Cr, Cu, Fe, Mg, Mn,

Ni, Pb, S, Se, V, Zn, Sb, Si and Ti) in two fractions – extract and residue –

on the same sample of air particulate matter is described. The two-step

method was tested on the SRM NIST 1648 for equivalence with two

reference methods, the EMEP procedure for ions extraction and the EN

12341 standard for the elemental determination of the PM10 and is suitable

for application to small sample amounts (less than 1 mg of particulate

matter is needed), i.e. those collected by daily low volume filter sampling.

Performance times of the procedure were optimised to meet the target of

routine application for large scale monitoring samples. A single ultrasonic-

assisted extraction of air particulate matter is performed in 0.01mol/L

acetate buffer at pH 4.5, followed by IC ions analysis and ICP-OES

elemental analysis of the extract and by ICP-OES elemental analysis of the

mineralized residue after dissolution by microwave-assisted digestion with

a HNO3/H2O2 mixture. Using a pH buffered extracting solvent was

preferred to water or diluted acid solutions to improve the reproducibility

of metals extraction with respect to existing leaching methods; the

influence of pH, nature and concentration of the buffer solution and

extraction time on analytes concentration in the extract is discussed. Values

of ions extraction and elements recoveries resulted fairly equivalent with

those obtained by the reference methods. The study was also extended to

some non-certified elements (Mg, S, Sb, Si and Ti) for their environmental

significance. Elements recoveries were obtained as sum of the extract and

residue fractions and were comparable with those obtained by direct

dissolution. Standard deviations were within 10% for almost all detected

ions and elements.

Type of sample: air particulate matter

Sample amount: 1 to 2 g of extracted sample

Microwave oven (model): Ethos Touch Control (Milestone Corporation,

Sorisole, Italy)


Heating: A two-step temperature-time program was performed. In the first

step the temperature was linearly increased to 180 ºC in 8 min with a

maximum power of the rotating magnetron of 650 W. In the second step

the temperature was kept at 180 ºC for 15 min.


Reagents: 4 mL of HNO3 and 2 mL of H2O2 30% (m/v)

Pretreatment general aspects:

Detection technique: ICP-OES and IC

Analytes: NO3−, SO4

2−, Cl−, Na+, Mg2+, NH4+,Ca2+ (by IC) and Al, As, Cd,

Cr, Cu, Fe, Mg, Mn, Ni, Pb, S, Se, V, Zn, Sb, Si and Ti by ICP-OES

Development of a radiochemical separation for selenium with the aim

of measuring its isotope 79 in low and intermediate nuclear wastes by

ICP-MS

Aguerre, S. and Frechou, C., Talanta, 69 (3), 565-571, 2006

Abstract

Selenium (Se) 79 is a beta emitter produced from 235U fission thus

occurring as one of the fission products found in nuclear reactors. Due to

its long half life (about 105 years), 79Se is one of the radionuclides of

interest for the performance of assessment studies of waste storage or

disposal. Thus, the National Radioactive Waste Management Agency

(Andra, France) requests its monitoring in wastes packages before their

disposal in specific sites. Measurement of 79Se is difficult owing to its trace

level concentration and its low activity in nuclear wastes. A radiochemical

procedure has to be carried out in order to separate selenium from the

matrix and to concentrate it before the measurement with a mass

spectrometric or a nuclear technique. The beginning of the development is

presented in this paper. The optimized protocol firstly developed in view of

an ICP-MS measurement, includes five steps based on microwave

digestion, evaporation and separations on ion exchange resins. It was tested

first on synthetic solutions and was optimized in order to be applicable to a

large number of sample types. The recoveries of the whole procedure were

evaluated using natural 82Se or the gamma emitter 75Se as a radioactive

spiker. Then, the protocol was applied to two solid samples spiked with

natural selenium, a glass microfiber filter and an ion exchange resin, and

two liquid samples spiked with 75Se, a synthetic solution and an effluent.

The yields obtained for both samples ranged from 70 up to 80%.

Type of sample: glass microfibre filters, anion exchange resin and a

effluent obtained from a nuclear liquid waste treatment plant


Microwave oven (model): Mars 5 (CEM Corporation, Matthews, NC,

USA)


Heating: 30 min, at 190 °C and 600 W


Reagents: 10 mL of HNO3 65% (v/v) and eventually 5 mL of HF 48%

(v/v) (in case of matrices containing silicium compounds).


Detection technique: ICP-MS, HG-AAS and Gamma spectrometry

Analytes: 79Se, 75Se, 82Se

Elemental analysis of silicon based minerals by ultrasonic slurry

sampling electrothermal vaporisation ICP MS

Rodríguez, P. F., Gayón, J. M. M. and Medel, A. S., Talanta, 68 (3), 869-

875, 2006

Abstract

Ultrasonic slurry sampling electrothermal vaporisation inductively coupled

plasma mass spectrometry (USS-ETV-ICP-MS) was applied to the

elemental analysis of silicate based minerals, such as talc or quartz, without

any pre-treatment except the grinding of the sample. The electrothermal

vaporisation device consists of a tungsten coil connected to a home-made

power supply. The voltage program, carrier gas flow rate and sonication

time were optimised in order to obtain the best sensitivity for elements

determined. The relationship between the amount of sample in the slurry

and the signal intensity was also evaluated. Unfortunately, in all cases,

quantification had to be carried out by the standard additions method owing

to the strong matrix interferences. The global precision of the proposed

method was always better than 12%.The limits of detection, calculated as

three times the standard deviation of the blank value divided by the slope of

the calibration curve, were between 0.5 ng/g for As and 3.5 ng/g for Ba.

The method was validated by comparing the concentrations found for Cu,

Mn, Cr, V, Li, Pb, Sn, Mg, U, Ba, Sr, Zn, Sb, Rb and Ce using the

proposed methodology with those obtained by conventional nebulisation

ICP-MS after acid digestion of the samples in a microwave oven. The

concentration range in the solid samples was between 0.2 μg/g for Cr and

60 μg/g for Ba. All results were statistically in agreement with those found

by conventional nebulisation.

Type of sample: silicon based minerals




Heating: 2 min at 200 W, 3.5 min at 400 W, 7 min at 700 W and 18 min at

0 W.


Reagents: 3 mL of HNO3 65% (v/v) and 2 mL of HF 48% (v/v)



Analytes: Cu, Mn, Cr, V, Li, Pb, Sn, Mg, U, Ba, Sr, Zn, Sb, Rb and Ce

Ion chromatography determination of heavy metals in airborne

particulate with preconcentration and large volume direct injection

Bruno, P., Caselli, M., Gennaro, G., Ielpo, P., Ladisa, T. and Plancentino,

C.M., Chromatographia, 64 (9-10), 537-542, 2006

Abstract

A flow injection analysis system with on-line enrichment was developed

for simultaneous determination of trace levels of Cu2+, Ni2+, Zn2+, Co2+,

Mn2+, Cd2+, Pb2+ and Fe3+, by high-performance ion chromatography

(HPIC) with spectrophotometric detection. It is a highly sensitive and low

cost alternative methodology. Ion Pac CS5A was used as the analytical

column with eluent composition of sodium nitrate 160 mM and oxalic acid

36 mM. Quantification after post-column reaction with PAR allows

detection limits between 0.5 and 5.0 ppb to be attained. The total analysis

time is less than 30 min. The proposed procedure was compared with a

large volume direct injection method using loop volumes up to 5 mL. Both

procedures were applied to the analysis of heavy metals in the PM10

fraction of atmospheric particulate samples. Airborne pollutants such as

nickel and cobalt can be quantified in 24 h samples of particulate matter at

concentrations of a few ng/m3.

Type of sample: Atmospheric particulate

Sample amount: The sampling times were 24 h. The nominal flow was

1.17 m3/min

Microwave oven (model): Ethos D (Milestone Corporation, Sorisole,

Italy)


Heating: The particulate was extracted by digesting the membrane in a

microwave wet digester with concentrated HNO3. This process took place

into two steps. In the first digestion step the filter portion is put in a 50 mL

quartz flask, filled with 6 mL HNO3 and the quartz flask housed in a Teflon


vessel. After the digestion step, the vessel is put in an ‘open module’ with a

valve system which allow the nitric vapours to reach the Aspivap module,

where they are neutralized.


Reagents: 6 mL HNO3 concentred

Pretreatment general aspects: Particulate sampling was performed using

a Graseby–Andersen high volume sampler (mod 1200) equipped with a

volumetric flow controller and a size selective inlet (SSI), allowing the

collection of particles with aerodynamic diameter < 10 μm.

Detection technique: HPLC

Analytes: Cu, Ni, Zn, Co, Mn, Cd, Pb and Fe

Lanthanum and lanthanides in atmospheric fine particles and their

apportionment to refinery and petrochemical operations in Houston,

TX

Kulkarni, P., Chellam, S. and Fraser, M. P., Atmospheric Environment, 40

(3), 508–520, 2006

Abstract

A study was conducted in Houston, TX focusing on rare earth elements

(REEs) in atmospheric fine particles and their sources. PM2.5 samples were

collected from an ambient air quality monitoring site (HRM3) located in

the proximity of a large number of oil refineries and petrochemical

industries to estimate the potential contributions of emissions from

fluidized-bed catalytic cracking operations to ambient fine particulate

matter. The elemental composition of ambient PM2.5, several commercially

available zeolite catalysts, and local soil was measured after microwave

assisted acid digestion using inductively coupled plasma-mass

spectrometry. Source identification and apportionment was performed by

principal component factor analysis (PCFA) in combination with multiple

linear regression. REE relative abundance sequence, ratios of La to light

REEs (Ce, Pr, Nd, and Sm), and enrichment factor analysis indicated that

refining and petrochemical cat cracking operations were predominantly

responsible for REE enrichment in ambient fine particles. PCFA yielded

five physically meaningful PM2.5 sources: cat cracking operations, a source

predominantly comprised of crustal material, industrial high temperature

operations, oil combustion, and sea spray. These five sources accounted for

82% of the total mass of atmospheric fine particles (less carbon and

sulfate). Factor analysis confirmed that emissions from cat cracking

operations primarily contributed to REE enrichment in PM2.5 even though

they comprised only 2.0% of the apportioned mass. Results from this study

demonstrate the need to characterize catalysts employed in the vicinity of

the sampling stations to accurately determine local sources of atmospheric

REEs.

Type of sample: atmospheric fine particles, soil, FCC catalysts and

automobile catalyst



USA)

Vessel material: PTFE-PFA

Heating: in the first stage, a combination of 48% hydrofluoric acid and

65% nitric acid was used to extract elements associated with siliceous

matter, which was present in significant amount in all the samples. HF was

employed in stoichiometric excess to ensure the complete dissolution of the

silicon matrix. Boric acid was added during the second digestion stage to

mask any excess HF and dissolve fluoride precipitates; a 20 min dwell time

for each stage and temperature and pressure set points of 200 °C and

12.92 atm

Number of samples simultaneously digested: -

Reagents: 5 mL HNO3 65% (v/v) + 0.4 mL HF 48% (v/v) + 2.4 mL of 5%

H3BO3 (FCC catalysts, automobile catalysts and soils); 2.5 mL HNO3 65%

(v/v) + 3 μL HF 48% (v/v) + 24 μL of 5% H3BO3 (particulate matter)



Analytes: Al, As, Ba, Cd, Ce, Co, Cr, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ho,

K, La, Lu, Mg, Mo, Mn, Na, Nd, Ni, Pb, Pr, Rb, Sc, Se, Si, Sm, Sr, Tb, Ti,

Tm, U, V, Y, Yb, Zn and Zr

Microwave assisted sample preparation for determining water-soluble

fraction of trace elements in urban airborne particulate matter:

evaluation of bioavailability

Karthikeyan, S., Joshi, U. M. and Balasubramanian, Analytica Chimica

Acta, 576 (1), 23-30, 2006

Abstract

The feasibility of using two different microwave-based sample preparation

methods was investigated to determine the total and water-soluble trace

metal fraction in airborne particulate matter. The extraction techniques

were then applied to urban particulate matter of different sizes in order to

evaluate their bioavailability of associated trace metals. While a

combination of HNO3-HF-H2O2 was used for the total trace metal fraction

of particulate matter, water was employed for the microwave-assisted

extraction of water-soluble trace metal fractions. Inductively coupled

plasma-mass spectrometry (ICP-MS) was used for the analysis of trace

elements. The experimental protocol for the microwave assisted digestion

was established using two different SRMs (1648, urban particulate matter

and 1649a, urban dust). In the case of water-soluble trace metal fraction,

the quantities extracted from the SRMs were compared between ultrasonic

and microwave-assisted extractions, and there was a good agreement

between the two extraction methods. Blanks values and limits of detection

(LODs) for total and water-soluble trace metal concentrations were

determined for three different filter substrates (Teflon, Zeflour, and Quartz).

Subsequently, the proposed digestion method was evaluated for its

extraction efficiency with these filter substrates. Finally, the real-world

application of the proposed microwave-based sample preparation methods

was demonstrated by analyzing trace elements in airborne particulate

samples collected from different outdoor environments in Singapore. The

solubility of 11 trace elements detected in the particulate samples is

quantified.

Type of sample: urban airborne particulate matter


Microwave oven (model): MLS 1200 Mega, Milestone Corporation,

Sorisole, Italy


Heating: Step 1: 5 min, 250 W, 95 °C. Step 2: 5 min, 400 W, 120 °C. Step

3: 2 min, 600 W, 130 °C (maximum temperature 300 °C). For evaluation of

water-soluble metals extractions were performed using microwave energy

of 100 W for 5min.


Reagents: 4 mL HNO3 + 2 mL H2O2 + 0.2 mL HF



Analytes: As, Co, Cu, Cd, Cr, Fe, Mn, Ni, Pb, V and Zn

Monitoring Pt and Rh in urban aerosols from Buenos Aires, Argentina

Bocca, B., Caimi, S., Smichowski, P. Gómez, D. and Caroli, S., Science of

the Total Environment, 358 (1-3), 255-264, 2006

Abstract

Vehicular traffic is the main source of platinum group elements (PGEs) in

highly populated urban areas like Buenos Aires where a traffic density of

1.500.000 vehicles day-1 (corresponding to 7500 vehicles km-2) is

estimated. Since there is no information on the levels of PGEs in Buenos

Aires, a pilot study was undertaken to ascertain the amount of two major

PGEs namely Pt and Rh, in the atmosphere of this city. To this end, 49

samples of PM-10 particulate matter were collected during 7 days in seven

representative sampling sites located downtown Buenos Aires and spread

over an area of about 30 km2. The collection of particulate matter was

performed on ash-free glass-fiber filters using high volume samplers with

PM-10 sampling heads. Filters loaded with the particulate matter were

subjected to microwave (MW)-assisted acid digestion using a combination

of HNO3, HF and HClO4. The resulting solutions were evaporated and then

diluted with 0.1 mol/L HCl. Analyses were performed by sector field

inductively coupled plasma-mass spectrometry (SF-ICP-MS) and special

attention was paid to the control of mass interferences. Statistical analysis

was performed on the experimental data obtained for the element

concentrations taking also into account local meteorological data for the

monitored period. The highest concentrations of Pt and Rh were detected at

two sites (Hospital Alemán and Casa Rapallini) located in streets with

traffic consisting mostly of passenger cars. The Pt content (in pg m-3) in

airborne particulate matter was found to vary from 2.3 to 47.7, with a mean

value of 12.9±7, and that of Rh from 0.3 to 16.8, with a mean value of

3.9±2.8. These concentrations are by far below the levels for which adverse

health effects might be expected to occur, i.e., around 100 ng/m. On the

other hand, monitoring of PGEs should be carried out in a systematic

fashion to detect possible dramatic increases from today’s levels.

Type of sample: urban aerosols


Microwave oven (model): MLS 1200 Mega (Milestone Corporation,

Sorisole, Italy)


Heating: Step 1: 250 W, 5 min. Step 2: 0 W, 5 min. Step 3: 400 W, 5 min;

Step 4: 0 W, 5 min. Step 5: 600 W, 5 min (three cycles were carried out

and 1 mL of HF was added before each new cycle started)


Reagents: 5 mL HNO3 + 2 mL HF + 2 mL HClO4

Pretreatment general aspects: the APM-loaded glass-fiber filters (with an

active surface of about 500 cm2) were weighed and then aliquots

corresponding to one fourth of the entire surface were sub-sampled from

each filter and their individual weights were recorded. The material

deposited on the filters turned out to be homogeneously distributed as the

weight of each quarter was approximately the same (about 0.023 g). The

samples thus obtained were cut in small fragments by means of non-

contaminating tungsten–carbide scissors and put into high pressure vessels.


Analytes: Pt and Rh

Validation of a field filtration technique for characterization of

suspended particulate matter from freshwater. Part II. Minor, trace

and ultra trace elements

Odman, F., Ruth, T., Rodushkin, I. and Pontér, C., Applied Geochemistry,

21 (12), 2112-2134, 2006

Abstract

A field filtration method for the concentration and separation of suspended

particulate matter (SPM) from freshwater systems and the subsequent

determination of minor, trace and ultra trace elements (As, Ba, Be, Cd, Co,

Cr, Cs, Cu, Ga, Hf, Mo, Nb, Ni, Pb, Rb, Sb, Sc, Sn, Sr, Ta, Th, Tl, U, V,

W, Zn and Zr) is validated with respect to detection limits, precision and

bias. The validation comprises the whole procedure including filtration,

sample digestion and instrumental analysis. The method includes two

digestion procedures (microwave acid digestion and alkali fusion) in

combination with inductively coupled plasma atomic emission

spectrometry (ICP-AES) and inductively coupled plasma quadrupole mass

spectrometry (ICP-QMS). Total concentrations of these 27 trace and minor

elements have been determined in suspended particulate matter (SPM)

from lake and river water with low levels of suspended solids (< 2 mg/L

DW), and a wide range of element concentrations. The precision of the

method including filtration, digestion and instrumental determination

ranges between 8% and 18% RSD for most elements on a dry weight basis.

Higher recovery after acid digestion is found for some elements, probably

because of volatilization or retention losses in the fusion procedure. Other

elements show higher recovery after fusion, which is explained by more

efficient decomposition of refractory mineral phases relative to the non-

total acid digestion. Non-detectable concentrations of some elements are

reported due to small differences between blank filter levels and the

amounts of elements present on the filters after sampling. The method

limits of detection range between 0.7 ng and 2.65 μg, as estimated from the

blank filter samples. These detection limits are 10–550 times higher

compared to the corresponding instrumental limits of detection. The

accuracy and bias of the overall analytical procedure was assessed from

replicate analysis of certified reference materials. A critical evaluation of

the instrumental capabilities of the ICP-QMS instrumentation in

comparison with a double focusing sector field plasma mass spectrometry

technique (ICP-SFMS) is also included. It was found that a modified

microwave acid digestion procedure in combination with ICP-SFMS could

replace ICP-AES determinations and fusion digestions for most of the

investigated elements. Guidelines and limitations for this time- and labour-

efficient procedure, offering accurate results for the majority of elements

studied are discussed.

Type of sample: filters with suspended particulate matter (SPM) from

freshwater

Sample amount: 2 filters

Microwave oven (model): MDS 81D (CEM, Corporation, Matthews, NC,

USA)

Vessel material: PFA

Heating: 150 W for 40 min, 200 W for 30 min, 260 W for 30 min, 200 W

for 30 min and 260 W for 30 min


Reagents: 8 mL of concentrated HNO3, 1 mL of H2O2 30% (m/v) and 10-

300 μL of concentrated HF



Analytes: As, Ba, Be, Cd, Co, Cr, Cs, Cu, Ga, Hf, Mo, Nb, Ni, Pb, Rb, Sb,

Sc, Sn, Sr, Ta, Th, Tl, U, V, W, Zn and Zr

A comparative study of chemical modifiers in the determination of

total arsenic in marine food by tungsten coil electrothermal atomic

absorption spectrometry

Bruhn, C. G., Bustos, C. J., Sáez, K. L., Neira, J. Y. and Alvarez, S. E.,

Talanta, 71 (1), 81–89, 2007

Abstract

Three platinum group elements (Pd, Ir and Rh) both in solution and in pre-

reduced form, and also combined with Mg(NO3)2 or ascorbic acid, were

assessed as possible chemical modifiers on the atomization of As in digest

solutions of seafood matrices (clam and fish tissue) by tungsten coil

electrothermal atomic absorption spectrometry (TCA-AAS) and compared

without a modifier. Of 28 modifier alternatives in study including single

form and binary mixtures, and based on maximum pyrolysis temperature

without significant As loss and best As absorbance sensitivity during

atomization, three modifiers: Rh (0.5 g), Ir (1.0 g) and Rh (0.5 g) +

ascorbic acid (0.5 g), at optimum amounts were pre-selected and compared.

The definitive modifier (rhodium (0.5 g)) was selected by variance

analysis. The mean within-day repeatability was 3% in consecutive

measurements (25–300 g/L) (three cycles, each of n = 6) and showed good

short-term stability of the absorbance measurements. The mean

reproducibility was 4% (n = 18 in a 3-day period) and the detection limit

(3σblank/slope) was 42 pg (n = 16). Quantitation was by standard additions

to compensate for matrix effects not corrected by the modifier. Three

sample digestion procedures were compared in fish and clam tissue

samples: microwave acid digestion alone (A) or combined with the

addition of 2% (m/v) K2S2O8 solution followed either by UV photo-

oxidation (B) or re-digestion in a thermal block (C). The accuracy was

established by determination of As in certified reference material of

dogfish muscle (DORM-2). Procedures B and C showed good recoveries

(102% (n = 4) and 103% (n = 7), respectively), whereas procedure A was

not quantitative (85%). The methodology is simple, fast, reliable, of low

cost and was applied to the determination of total As in lyophilized samples

of clam and fish collected in the Chilean coast.

Kind of sample: marine food (clam and fish tissue)


Microwave oven model: MLS-1200 MEGA Milestone (Bergamo, Italy)

Vessel material: TFM

Heating: Step 1: 1 min, 250 W. Step 2: 1 min, 0 W. Step 3: 5 min, 250 W.

Step 4: 5 min, 400 W. Step 5: 5 min 650 W. Step 6: 5 min, 0 W.


Reagents: HNO3/H2O2 (6:1) (according to manufacturer’s suggested

program)

Pretreatment general aspects: not informed

Detection technique: TCA-AAS

Analytes: As

Analytical procedure for total mercury determination in fishes and

shrimps by chronopotentiometric stripping analysis at gold film

electrodes after microwave digestion

Augelli, M. A., Munoz, R. A. A., Richteru, E. M., Antagallo, M. I. and

Angnes, L., Food Chemistry, 101 (2), 579-584, 2007

Abstract

A method for the total mercury determination in fish and shrimps

employing chronopotentiometric stripping analysis on gold film electrodes

is described. Fish and shrimp tissues were digested using a microwave

oven equipped with closed vessels. We developed a microwave heating

program which decomposed all the samples employing diluted nitric acid

and hydrogen peroxide. The proposed method was validated by analyzing a

certified reference material and then applied for diferent fish species from

fresh water and seawater acquired in local markets of São Paulo city,

Brazil. The Brazilian legislation establishes 0.5 and 1 mg per kilogram of

fish as upper limit of mercury for omnivorous and predator species,

respectively. Except for blue shark tissues, the mercury content was

situated below 0.5 µg/g for all the analyzed samples. The detection limit of

the proposed method was calculated as 5 ng/g of sample utilizing 5 minutes

of electrodeposition (+300 mV vs. Ag/AgCl) on the gold electrode.

Type of sample: Fish and Shrimps

Sample amount: 0.1 – 4.0 g

Microwave oven (model): MDS 2000, CEM Corporation, Mattew, NC,

USA


Heating: Step 1: 10 min at 3.40 atm. Step 2: 10 min at 4.08 atm. Step 3:

6 min at 5.44 atm. Step 4: 6 min at 6.80 atm. Step 5: 10 min at 5.44 atm


Reagents: 1 mL water + 2 mL HNO3 70% + 1 mL H2O2 30%


Detection technique: CSA combined on gold film electrods

Analytes: Hg

Comparison of extraction procedures for methylmercury

determination by a SPME-GC-AFS system

Abrankó, L., Kmellár, B. and Fodor, P., Microchemical Journal, 85 (1),

122–126, 2007

Abstract

In this study the comparison of three different alkaline extraction

techniques carried out with methanolic NaOH followed by phenylation

derivatization for the determination of methylmercury in marine fish was

performed. The investigated three methods differed in the technique how

the extraction assisting energy was introduced to the sample. Namely,

closed vessel ultrasonic bath, an open vessel technique using an ultrasonic

probe and the microwave assisted extraction procedures were characterized

and optimized. Optimum values of 3 h at 75 °C for the ultrasonic bath, 25

min for the ultrasonic probe and 6 min at 60 W for the microwave method

were obtained. All three methods were validated using the BCR-464 tuna

fish certified reference material.

Type of sample: fish, tuna fish BCR 464


Microwave oven (model): MDS-81D (CEM Corporation, Matthews, NC,

USA)

Vessel material: Teflon-perfluoroalkoxy (PFA)

Heating: 20–120 W for 2–6 min.


Reagents: 20 mL of 18% (w/v) NaOH in methanol


Detection technique: SPME-GC-AFS

Analytes: MeHg

Determination of metals in marine species by microwave digestion and

inductively coupled plasma mass spectrometry analysis

Yang, K. X. and Swami, K., Spectrochimica Acta B, 62 (10), 1177-1181,

2007

Abstract

A microwave digestion method suitable for determination of multiple

elements in marine species was developed, with the use of cold vapor

atomic spectrometry for the detection of Hg, and inductively coupled

plasma mass spectrometry for all of the other elements. An optimized

reagent mixture composed of 2 mL of HNO3, 2 mL of H2O2 and 0.3 mL of

HF used in microwave digestion of about 0.15 g (dry weight) of sample

was found to give the best overall recoveries of metals in two standard

reference materials. In the oyster tissue standard reference material (SRM

1566b), recoveries of Na, Al, K, V, Co, Zn, Se, Sr, Ag, Cd, Ni, and Pb

were between 90% and 110%; Mg, Mn, Fe, Cu, As, and Ba recoveries were

between 85% and 90%; Hg recovery was 81%; and Ca recovery was 64%.

In a dogfish certified reference material (DORM-2), the recoveries of Al,

Cr, Mn, Se, and Hg were between 90% and 110%; Ni, Cu, Zn, and As

recoveries were about 85%; and Fe recovery was 112%. Method detection

limits of the elements were established. Metal concentrations in flounder,

scup, and blue crab samples collected from coastal locations around Long

Island and in the Hudson River estuary were determined.

Type of sample: marine species


Microwave oven (model): CEM MARS 5, CEM Corp., Matthews, NC,

USA


Heating: The samples were digested in two steps. Step 1: 110 °C with 20

min at 600 W, followed by a dwell time of 5 min at 110 °C and an initial

cooling in the microwave oven for 5 min. The vessels were then removed

from the oven and cooled in a freezer -20 °C for an hour, after which they

were vented and opened. Step 2: 200 °C with 10 min at 1200 W, followed

by a dwell time of 10 min at 200 °C. They were again cooled in the

microwave oven for 5 min and in a freezer at -20 °C for 1 hour, after which

they were vented and opened.


Reagents: 2 mL HNO3 conc + 2 mL H2O2 30% + 0.3 mL HF conc


Detection technique: CVAAS, ICP-MS

Analytes: Be, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As,

Se, Sr, Mo, Ag, Cd, Sn, Sb, Ba, Tl, Pb, Hg

Determination of trace metals in canned fish marketed in Turkey

Mustafa, T. and Mustafa, S., Food Chemistry, 101 (4), 1378-1382, 2007.

Abstract

The levels of trace metals of canned fish samples collected from markets in

Turkey were determined by flame and graphite furnace atomic absorption

spectrometry after microwave digestion. The accuracy of the method was

corrected by standard reference material (NRCC-DORM-2 Dogfish

Muscle). The contents of investigated trace metals in canned fish samples

were found to be in the range 1.10–2.50 µg/g for copper, 7.57–34.4 µg/g

for zinc, 0.90–2.50 µg/g for manganese, 10.2–30.3 µg/g for iron, 0.96–3.64

µg/g for selenium, 0.45–1.50 µg/g for aluminium, 0.97–1.70 µg/g for

chromium, 0.42–0.85 µg/g for nickel, 0.09–0.40 µg/g for lead and 0.06–

0.25 µg/g for cadmium. The results were compared with the literature

values.

Type of sample: canned fish


Microwave oven (model): Milestone Ethos D microwave closed system

maximum pressure 98.65 atm, maximum temperature 300 oC, Milestone

Corporation, Sorisole, Italy


Heating: Step 1: 2 min for 250 W. Step 2: 2 min for 0 W. Step 3: 6 min for

250 W. Step 4: 5 min for 400 W. Step 5: 8 min for 550 W. Step 6:

ventilation 8 min.


Reagents: 6 mL HNO3 concentraded + 2 mL H2O2 30% (m/v)


Detection technique: FAAS and GFAAS equipped with HGA

Analytes: Cu, Zn, Mn, Fe, Se, Al, Cr, Ni, Pb and Cd.

Improved microwave-assisted wet digestion procedures for accurate Se

determination in fish and shellfish by flow injection-hydride

generation-atomic absorption spectrometry

Lavilla, I., González-Costas, J. M. and Bendicho C., Analytica Chimica

Acta, 591 (2), 225-230, 2007

Abstract

Accurate determination of Se in biological samples, especially fish and

shellfish, by hydride generation techniques has generally proven

troublesome owing to the presence of organoselenium that cannot readily

converted into inorganic selenium under usual oxidizing conditions.

Further improvements in the oxidation procedures are needed so as to

obtain accurate concentration values when this type of samples is analyzed.

Microwave-assisted wet digestion (MAWD) procedures of seafood based

on HNO3 or the mixture HNO3/H2O2 and further thermal reduction of the

Se(VI) formed to Se(IV) were evaluated. These procedures were as

follows: (I) without H2O2 and without heating to dryness; (II) without H2O2

and with heating to dryness; (III) with H2O2 and without heating to dryness;

(IV) with H2O2 and with heating to dryness. In general, low recoveries of

selenium are obtained for several marine species (e.g., crustaceans and

cephalopods), which may be described to the presence of Se forms mainly

associated with nonpolar proteins and lipids. Post-digestion UV irradiation

proved very efficient since not only complete organoselenium

decomposition was achieved but also the final step required for

prereduction of Se (VI) into Se (IV) (i.e. heating at 90 °C for 30 min in 6 M

HCl) could be avoided. With the MAWD/UV procedure, the use of strong

oxidizing agents (persuphate, etc.) or acids (e.g. perchloric acid) which are

typically applied prior to Se determination by hydride generation

techniques is overcome, and as a result, sample pre-treatment is

significantly simplified. The method was successfully validated against

CRM DOLT-2 (dogfish liver), CRM DORM-2 (dogfish muscle) and CRM

TORT-2 (lobster hepatopancreas). Automated ultrasonic slurry sampling

with electrothermal atomic absorption spectrometry was also applied for

comparison. Total Se contents in ten seafood samples were established. Se

levels ranged from 0.7 to 2.9 μg/g.

Type of sample: fish and shellfish


Microwave oven (model): Model MDS-2000 and Metrohm

UV-digester Model 705, CEM Corporation, Matthews, NC, USA

Vessel material: PTFE and quartz

Heating: Step 1: 300 W, 2 min. Step 2: 300 W, 2 min. Step 3: 300 W,

7 min.


Reagents: 5 mL HNO3 + 0.5 mL H2O2 33% m/v

Pretreatment general aspects: The samples were homogenized using a

mixer and then freeze-dried and ground in the ball mill. After cooling, the

prereduction of Se (VI) into Se (IV) was performed by adding 6 mol/L HCl

and heating at 90°C for 30min. The solutions were diluted to 50 mL. The

resulting solution of re-composing the digested sample with 10 mL of

6 mol/L HCl was subjected to ultraviolet irradiation for 10 min and then

diluted to 50 mL.

Detection technique: FI-HG-AAS

Analytes: Se

An attempt to differentiate HPLC-ICP-MS selenium speciation in

natural and selenised Agaricus mushrooms using different species

extraction procedures

Huerta, V. D., Sánchez, M. L. F., and Sanz-Medel., Analytical and

Bionalytical Chemistry, 384 (4), 902-907, 2006

Abstract

Total determination and speciation analysis of Se in commercial and

selenised Agaricus mushrooms have been performed to investigate the Se

species naturally occurring in non-enriched mushrooms as well as those

present in specimens grown in a Se-enriched medium. Mushroom aqueous

and enzymatic extracts have been analysed by three complementary

chromatographic separation mechanisms (size-exclusion, anion-exchange

and reversed-phase) coupled to an inductively coupled plasma mass

spectrometer with an octopole reaction system. Post-column isotope

dilution analysis has been used on-line with the separations for

quantification of the Se species eluted. The 78Se-to-77Se isotope ratio was

monitored after adequate corrections for both total determinations and Se

species quantitative speciation. The results showed marked differences not

only in total Se contents but also in Se species found in the two types of

Agaricus mushrooms investigated. Selenomethionine was detected in both

of them (free in commercial mushrooms and incorporated into proteins in

selenised ones) together with a number of unknown seleno compounds.

Type of sample: mushrooms


Microwave oven (model): MLS-1200 Milestone, Sorisole, Italy


Heating: Step 1: 250 W for 1 min. Step 2: 0 W for 2 min. Step 3: 250 W

for 2 min. Step 4: 700 W for 7.5 min. Step 5: 0 W for 15 min



Reagents: 1.5 mL of HNO3 + 1.5 mL of H2O2

Pretreatment general aspects: Natural Agaricus mushrooms were freeze-

dried, while the lyophilised Se-enriched sample was provided.


Analytes: Se

Application of double-spike isotope dilution for the accurate

determination of Cr(III), Cr(VI) and total Cr in yeast

Yang, L., Ciceri, E., Mester, Z. and Sturgeon, R.E., Analytical and


Abstract

A method is presented for the simultaneous determination of Cr(III) and

Cr(VI) in yeast using species-specific double-spike isotope dilution

(SSDSID) with anion-exchange liquid chromatography (LC) separation and

sector field inductively coupled plasma mass spectrometric (SF-ICP-MS)

detection. Total Cr is quantitated using SF-ICP-MS. Samples were digested

on a hot plate at 95±2 °C for 6 h in an alkaline solution of 0.5 M NaOH and

0.28 mol/L Na2CO3 for the determination of Cr(III) and Cr(VI), whereas

microwave-assisted decomposition with HNO3 and H2O2 was used for the

determination of total Cr. Concentrations of 2.014±16, 1.952±103 and

76±48 mg/kg (one standard deviation, n=4, 3, 3), respectively were

obtained for total Cr, Cr(III) and Cr(VI) in the yeast sample. Significant

oxidation of Cr(III) to Cr(VI) (24.2±7.6% Cr(III) oxidized, n = 3) and

reduction of Cr(VI) to Cr(III) (37.6±6.5% Cr(VI) reduced, n = 3 ) occurred

during alkaline extraction and subsequent chromatographic separation at

pH 7. Despite this significant bidirectional redox transformation,

quantitative recoveries for both Cr(III) and Cr(VI) were achieved using the

SSDSID method. In addition, mass balance between total Cr and the sum

of Cr(III) and Cr(VI) concentrations was achieved. Method detection limits

of 0.3, 2 and 30 mg/kg were obtained for total Cr, Cr(VI) and Cr(III),

respectively, based on a 0.2 g sub-sample.

Type of sample: Yeast


Microwave oven (model): MDS-2100 (CEM Corporation, Matthews, NC,

USA)



Heating: : 10 min at 1.36 atm and 40% power; 10 min at 2.72 atm and

50% power; 10 min at 5.44 atm and 50% power; 20 min at 6.80 atm and

60% power; 30 min at 8.16 atm and 70% power.


Reagents: 5 mL HNO3 + 0.2 mL H2O2



Analytes: Cr

Application of Isotope Dilution Analysis for the Evaluation of

Extraction Conditions in the Determination of Total Selenium and

Selenomethionine in Yeast-Based Nutritional Supplements

Reyes, L. H., Gayón, J. M. M., Alonso, J. I. G. and Medel, A. S., Journal of

Agricultural and Food Chemistry, 54 (5), 1557-1563, 2006

Abstract

Isotope dilution analysis (IDA) has been used to quantify total selenium,

total solubilized selenium, and the selenomethionine (SeMet) amount in

yeast and yeast-based nutritional supplements after acid microwave

digestion and different enzymatic extraction procedures. For this purpose,

both a 77Se-enriched SeMet spike, previously synthesized and characterized

in our laboratory, and a 77Se- (VI) spike were used. In the analysis of the

nutritional supplements, the SeMet spike was added to the sample and

extracted under different conditions, and the 78Se/77Se and 80Se/77Se isotope

ratios were measured as peak area ratios after high-performance liquid

chromatography (HPLC) separation and inductively coupled plasma mass

spectrometry (ICP-MS) detection. The formation of SeH+ and mass

discrimination were corrected using a natural SeMet standard injected

every three samples. Similarly, total solubilized selenium was measured in

the extracts after enzymatic hydrolysis using the 77Se-enriched SeMet as a

spike by direct nebulization without a chromatographic separation. To

establish a mass balance, total selenium was also determined by IDA-ICP-

MS on the yeast tablets after microwave digestion using 77Se(VI) as a

spike. Results showed that all enzymatic procedures tested were able to

solubilize total selenium quantitatively from the solid. However, the

recovery for the species SeMet, the major selenium compound detected,

was seriously affected by the enzymatic procedure employed and also by

the matrix composition of the supplement evaluated. For the yeast sample,

SeMet recovery increased from 68 to 76% by the combined use of driselase

and protease. For the nutritional supplements, the two most effective

procedures appeared to be protease and driselase/protease, with a SeMet

recovery ranging from 49 to 63%, depending upon the supplement

evaluated. In the case of in vitro gastrointestinal enzymolysis, the results

obtained showed 26-37% SeMet recovery, while the rest of selenium was

solubilized as other unknown compounds (probably Se-containing

peptides).

Type of sample: nutritional supplements


Microwave oven (model): Microwave 1200 (Milestone Corporation,

Sorisole, Italy)


Heating: 250 W for 2 min and 450 W for 5 min.


Reagents: 3 mL of concentrated HNO3 and 0.5 mL of 30% H2O2 m/v


Detection technique: HPLC-ICP-MS and ICP-MS

Analytes: selenium species

Automated method for the total creatinine determination in

dehydrated broths

Avebal, C. C., Centurión, M. E., Lista, A. and Band, B. S. F., Analytical

Letters, 39 (2), 387-394, 2006

Abstract

In order to improve the quality control of dehydrated broth, a new

automated method was developed to determine total creatinine in

dehydrated broths. The sample pretreatment was coupled on-line with the

Flow Injection Analysis (FIA) system for analyte determination by the

classical Jaffé reaction, stopped flow methodology, and spectrophotometric

detection. The time consumed was reduced from 7 h, which is necessary

with the official method, to 25 min. The calibration graph is linear between

0.342–1.368 mg creatinine/100 mL. The relative standard deviation

(RSD%) was 1.7%, the sample throughput was 7 h-1, and the detection

limit was 0.185 mg creatinine/100 mL. The validation of the proposed

method was carried out with real samples. The obtained results were

compared with those obtained from the Association of Official Analytical

Chemists (AOAC) reference method.

Type of sample: dehydrated Broths

Sample amount: not informed

Microwave oven (model): Maxidigest MX 350 Prolabo, France


Heating: not informed


Reagents: HCl

Pretreatment general aspects: A suitable amount of the sample was

dissolved in 1.5 mol/L HCl. It was stirred for 10 min at 70– 80 °C.

Detection technique: UV-Vis spectrophotometer

Analytes: Creatinine


Certification of a new selenized yeast reference material (SELM-1) for

methionine, selenomethinone and total selenium content and its use in

an intercomparison exercise for quantifying these analytes

Mester, Z., Willie, S., Yang, L., Sturgeon, R., Caruso, J. A., Fernandéz, M.

L., Fodor, P., Goldschimidt, R. J., Goenaga-Infante, H., Lobinski, R.,

Maxwell, P., McSheehy, S., Polatajko, A., Sadi, B. B. M., Sanz-Medel, A.,

Scriver, C., Szpunar, J., Wahlen, R. and Wolf, W., Analytical and

Bionalytical Chemistry (1), 385, 168-180, 2006

Abstract

A new selenized yeast reference material (SELM-1) produced by the

Institute for National Measurement Standards, National Research Council

of Canada (INMS, NRC) certified for total selenium (2.059±64 mg/kg),

methionine (Met, 5.758±277 mg/kg) and selenomethionine (SeMet,

3.431±157 mg/kg) content is described. The ± value represents an

expanded uncertainty with a coverage factor of 2. SeMet and Met amount

contents were established following a methanesulfonic acid digestion of the

yeast using GC-MS and LC-MS quantitation. Isotope dilution (ID)

calibration was used for both compounds, using 13C-labelled SeMet and

Met. Total Se was determined after complete microwave acid digestion

based on ID ICP-MS using a 82Se spike or ICP OES spectrometry using

external calibration. An international intercomparison exercise was piloted

by NRC to assess the state-of-the-art of measurement of selenomethione in

SELM-1. Determination of total Se and methionine was also attempted.

Seven laboratories submitted results (2 National Metrology Institutes

(NMIs) and 5 university/government laboratories). For SeMet, ten

independent mean values were generated. Various acid digestion and

enzymatic procedures followed by LC ICP-MS, LC AFS or GC-MS

quantitation were used. Four values were based on species-specific ID

calibration, one on non-species-specific ID with the remainder using

standard addition (SA) or external calibration (EC). For total selenium,

laboratories employed various acid digestion procedures followed by ICP-

MS, AFS or GC-MS quantitation. Four laboratories employed ID

calibration, the remaining used SA or EC. A total of seven independent

results were submitted. Results for methionine were reported by only three

laboratories, all of which used various acid digestion protocols combined

with determination by GC-MS and LC UV. The majority of participants

submitted values within the certified range for SeMet and total Se, whereas

the intercomparison was judged unsuccessful for Met because only two

external laboratories provided values, both of which were outside the

certified range.

Type of sample: Selenium Enriched Yeast Certified Reference Material

(SELM-1)



USA)


Heating: 10 min at a pressure of 1.36 atm and 40% power, 10 min at

2.72 atm and 50% power, 10 min at 5.44 atm and 50% power, 20 min at

6.80 atm and 60% power, and 30 min at 8.16 atm and 70% power.


Reagents: 5 mL HNO3 + 0.2 mL H2O2



Analytes: Se

Chromium content in different kinds of Spanish infant formulae and

estimation of dietary intake by infants fed on reconstituted powder

formulae

Sola-Larrañaga, C. and Navarro-Blasco, I., Food Additives and

Contaminants, 23 (11), 1157-1168, 2006

Abstract

Chromium is well documented as an essential element for humans.

Trivalent chromium, the main chemical form found in foods, is essential

for maintaining normal glucose metabolism. Owing to analytical

difficulties, several literature reports of chromium content of foods,

especially for the lower levels, show large variability and should be

interpreted with caution. Zeeman background correction, transversely

heated graphite furnace atomic absorption spectrometry was used to

determine the chromium content of 104 different infant formulae (cow’s

milk and soy protein based) marketed in Spain following an acid-digestion

sample preparation procedure in a closed, pressurized and microwave

digestion unit. The mean and range of chromium values, regarding types

and main protein-based infant formulae are presented. Additionally, the

influence of the type of container used, the impact of industrial process

from different manufacturers and the physical state (powder and liquid

formulae) on chromium levels is also discussed. In general, the infant

formulae contain a higher chromium concentration than that found in

human milk (reference range: 0.20 ± 8.18 mg/L), particularly in the case of

hypoallergenic (18.16 ± 7.89 mg/L), lactose-free (11.37 ± 3.07 mg/L), pre-

term (11.48 ± 3.15 mg/L) and soya (10.43 ± 4.05 mg/L) formulae. The

maximum theoretical estimated intake of infants fed on the studied

formulae was lower than the upper limit safety for trivalent chromium of

1 mg/kg (14 mg/kg b.w. day-1) recommended by the experts of Council for

Responsible Nutrition amounting to about 10, 15–18 and 26% of the

standard (adapted and follow-up) and toddler, soya, lactose-free and pre-

term, and hypoallergenic formulae, respectively. Therefore, manufacturers

are called upon to make continued efforts to routinely monitor chromium

levels, particularly for specialised and pre-term formulae, and at the same

time, might consider the inclusion of labelling the levels of chromium at

least in these complex formulations.

Type of sample: infant formulae

Sample amount: 0.3-0.5 g or 3 mL

Microwave oven (model): Ethos Plus, Milestone Corporation, Sorisole,

Italy


Heating: Step 1: 25-170 °C for 10 min. Step 2: 170 °C for 10 min, both at

1000 W, followed immediately by ventilation at room temperature.

Digested samples were diluted to 10 mL in a volumetric flask with

ultrapure water and finally transferred topre-cleaned polypropylene tubes.

Solutions were stored frozen at -20 °C until analysis.


Reagents: 8 mL HNO3



Analytes: Cr

Determination of Cd and Pb in honey by SF-ICP-MS: Validation

figures and uncertainty of results

Frazzoli, C., D’Ilio, S. and Bocca, B., Analytical Letters, 40 (10), 1992-

2004, 2007

Abstract

A method based on microwave-assisted acid digestion of honey and

quantification of Cd and Pb by Sector Field Inductively Coupled Plasma

Mass Spectrometry was in-house validated and the combined uncertainty

was estimated according to the Eurachem/Citac Guide. Limits of detection

and quantification were 0.07 and 0.20 ng/g for Cd, and 0.70 and 2.10 ng/g

for Pb; recovery was 103.9% for Cd and 98.5% for Pb; repeatability was

10.7% for Cd and 18.5% for Pb; within-laboratory reproducibility was

15.2% for Cd and 21.4% for Pb. Relative combined uncertainty in honey

was 15% for Cd and 22 % for Pb, with the main contribution coming from

the within-laboratory reproducibility. The method showed robustness when

subjected to different working conditions and when applied to various

Italian honeys. Cadmium content ranged 0.2-1.37 ng/g and Pb

4.6-30.5 ng/g in flower honeys, while the highest concentrations were

presented by honeydew honeys.

Type of sample: honey


Microwave oven (model): MLS-1200 FKV Milestone, Sorisole, Italy


Heating: Step 1: 250 W, 2 min. Step 2: 0 W, 2 min. Step 3: 250 W, 5 min.

Step 4: 500 W, 5 min. Step 5: 650 W, 5 min. Step 6: 250 W, 5 min.

Number of simultaneously digested: not informed

Reagents: 6 mL HNO3 65% (v/v) + 1 mL H2O2 30% (m/v)

Pretreatment general aspects: Containers with honey were heated in a

water bath at 50 °C and sonicated for 10 min. After digestion, digests were

diluted to 15 g.


Analytes: Cd and Pb

Determination of chromium by GFAAS in slurries of fish feces to

estimate the apparent digestibility of nutrients in feed used in

pisciculture

Silva, F. A., Padilha, C. C. F., Pezzato, L. E., Barros, M. M. and Padilha, P.

M., Talanta, 69 (4), 1025-1030, 2006.

Abstract

This paper presents a simple, fast and sensitive method to determine

chromic oxide (used as a biological marker of fish feed) in samples of fish

feces by GFAAS through the direct introduction of slurries of the samples

into the spectrometer’s graphite tube. The standard samples of feces and of

fish feed containing 0.10–1.00 mg/kg of Cr2O3 were pre-frozen for 1 min in

liquid nitrogen and then ground a cryogenic mill for 2 min, which reduced

the samples grain size to less than 60 μm. The standard slurries were

prepared by mixing 20 mg of standard samples of fish feed or feces with

1 mL of a solution containing 0.05% (v/v) of Triton X-100 and 0.50% (v/v)

of suprapure HNO3 directly in the spectrometer’s automatic sampling glass.

The final concentrations of Cr2O3 present in the standard slurries were 2, 4,

8, 16 and 20 μg/L. After sonicating the mixture for 20 s, 10 μL of standard

slurries were injected into the graphite tube, whose internal wall was lined

with a metallic palladium film that acted as a permanent chemical modifier.

The limits of detection (LOD) and quantification (LOQ) calculated for 20

readings of the blank of the standard slurries (2%, m/v of feces or feed

devoid of minerals) were 0.81 and 2.70 μg/L of Cr2O3 for the standard

feces slurries, 0.84 and 2.83 μg/L of Cr2O3 for the standard feed slurries.

The proposed method was applied in studies of nutrient digestibility of

different fish feeds and its results proved compatible with the results

obtained from samples pre-mineralized by acid digestion.

Type of sample: fish feces and feed used in pisciculture


Microwave oven (model): DGT 100 (Provecto Analítica, Brazil)




Reagents: 2.5 mL of HNO3 conc. and 0.5 mL of H2O2 30% (m/v)

Pretreatment general aspects: the samples were cryogenically ground


Analytes: Cr

Determination of chromium, iron and selenium in foodstuffs of animal

origin by collision cell technology, inductively coupled plasma mass

spectrometry (ICP-MS), after closed vessel microwave digestion

Dufailly, V., Nöel, L. and Guérin, T., Analytica Chimica Acta, 565 (2),

214-221, 2006

Abstract

The determination of chromium (52Cr), iron (56Fe) and selenium (80Se)

isotopes in foodstuffs of animal origin has been performed by collision cell

technology (CCT) mode using an inductively coupled plasma mass

spectrometry (ICP-MS) as detector after closed vessel microwave

digestion. To significantly decrease the argon-based interferences at mass

to charge ratios (m/z): 52 (40Ar12C), 56 (40Ar16O) and 80 (40Ar40Ar), the

gas-flowrates of a helium and hydrogen mixture used in the hexapole

collision cell were optimised to 1.5 mL/min H2 and 0.5 mL/min He and the

quadrupole bias was adjusted daily between −2 and −15 mV. Limits of

quantification (LOQ) of 0.025, 0.086 and 0.041 mg/kg for Cr, Fe and Se,

respectively, in 6% HNO3 were estimated under optimized CCT conditions.

These LOQ were improved by a factor of approximately 10 for each

element compared to standard mode. Precision under repeatability,

intermediate precision reproducibility and trueness have been tested on

nine different certified reference materials in foodstuffs of animal origin

and on an external proficiency testing scheme. The results obtained for

chromium, iron and selenium were in all cases in good agreement with the

certified values and trueness was improved, compared to those obtained in

standard mode.

Type of sample: foodstuffs


Microwave oven (model): Multiwave 3000 (Anton Paar, Austria)




Reagents: 3 mL HNO3 65% (v/v) + 3 mL water



Analytes: Cr, Fe and Se

Determination of macro and trace element in multivitamins

preparations by inductively coupled plasma optical emission

spectrometry with slurry sample introduction

Krejcová, K., Kahoun, D., Cernohorsky, T. and Pouzar, M., Food

Chemistry, 98 (1), 171-178, 2006

Abstract

A slurry sampling technique has been utilized for elemental analysis of

multivitamins preparations using inductively coupled plasma-emission

spectrometry (ICP-OES). For results comparison, samples were

mineralized. Slurry concentration 0.1–0.2% m/v in 6% v/v HNO3, was

used. The calibration by water standard solutions, slurry standards and

standard additions were tested for determination above-mentioned elements

in slurries. The method offers good precision for macro elements (RSD

ranged from 5% to 10%). For in-home control sample, the measured

concentrations are in satisfactory agreement with independent laboratories.

For the analyzed multivitamin preparations, the found element

concentration is compared to amount declared by producer. The

concentrations of Ca, Mg, P, K, Fe, Mn, Zn, Cu and Cr, Ni, V were

determined in the range 1000–100,000 and 5–50 μg/g, respectively. The

slurry ICP-OES analysis was found to be suitable for quality control

monitoring of multivitamin preparations and could be useful as a routine

procedure.

Type of sample: multivitamin preparations


Microwave oven (model): BM 1 S/2 (Plazmatronika, Poznan)


Heating: power setting of 80% for 10 min and at 100% for 10 min. The

maximum total output of the microwave generator was 700 W.


Reagents: 6 mL of concentrated HNO3


Detection technique: ICP-OES

Analytes: Ca, Mg, P, K, Fe, Mn, Zn, Cu, Cr, Ni and V

Evaluation of contents in different bakery foods by electrothermal

atomic absorption spectrometer

Jalbani, N., Kazi, T. G., Jamali, M. K., Arain, B. M., Afridi, H. I. and

Baloch, A., Journal of Food Composition and Analysis, 20 (3-4), 226-231,

2007

Abstract

The present study provides the dietary intake of a non-essential metal,

aluminum (Al), in bakery products consumed in the urban areas of

Hyderabad, Pakistan. The contribution of the different bakery products to

the daily intake of Al was also evaluated. Samples of different branded and

non-branded bread and biscuits studied using electrothermal atomic

absorption spectrometry (ETAAS) prior to microwave assisted and

conventional wet acid digestion methods. Results were calculated in mg/kg.

The validity and accuracy of both procedures were checked by using

certified sample of beech leaves (BCR 100). Non-significant differences

were observed for P40.05 when comparing the values obtained by both

methods (paired t-test). The mean Al concentration of each branded and

non-branded biscuit samples were found in the range of 7.4–84.3 and 34.5–

70.2 mg/kg, respectively, while the analysis of branded and non-branded

bread revealed the presence of Al at concentration levels from 8.0 to 29.6

and 39.1 to 82.9 mg/kg, respectively. We observed that the levels of Al

were significantly higher in non-branded bread, biscuit and in some

branded products. The contribution of the bakery products to the daily

intake of Al, based on the consumption of 250 g bread or biscuit per day,

was found in the range of 1.9–21.1, 8.62–17.6, 2.0–7.4, and 9.5–20.7

mg/day, from all branded and non-branded biscuit and bread, respectively.

The limit of detection (LOD) and limit of quantitation (LOQ) of Al were

0.5 and 5 mg/L, respectively.

Type of sample: bakery foods


Microwave oven (model): Microwave System Milestone Corporation,

Sorisole, Italy







Analytes: Al

Evaluation of selenium behavior in thermospray flame furnace atomic


Rosini, F., Nascentes, C. C., Neira, J. Y. and Nóbrega, J. A., Talanta, 73

(5), 845-849, 2007

Abstract

The behavior of selenium in thermospray flame furnace atomic absorption

spectrometry (TS-FF-AAS) was studied and the developed procedure was

applied for selenium determination in biological materials after microwave-

assisted sample digestion. A sample volume of 600 μL was introduced into

the hot metallic Ni tube at a flow rate of 0.4 mL/min using water as carrier.

The limit of detection obtained for Se was 8.7 μg/L (3sblank/slope, n = 10),

which is 95-fold better than that typically obtained using FAAS. The

applicability of the TS-FF-AAS procedurewas evaluated for selenium

determination in biological materials. Certified reference materials of pig

kidney (BCR 186) and mussel (GBW 08571) were analyzed and a t-test

had not shown any statistically significant difference at a 95% confidence

level between determined and certified values for both materials. The

procedure was successfully applied for determination of Se in pig kidney

and shellfish. It was demonstrated that TS-FF-AAS improved the

performance of FAAS (flame atomic absorption spectrometry) for

determination of Se.

Type of sample: pig kidney and shellfish


Microwave oven (model): ETHOS-1600, Milestone, Sorisole, Italy

Vessel material: Teflon PFA®

Heating: Step 1: 200 W, 2 min, 150 oC. Step 2: 0 W, 2 min, 165 oC. Step 3:

300 W, 3 min, 180 oC. Step 4: 450 W, 3 min, 250 oC. Step 5: 520 W, 3 min,

240 oC. Ventilation: 0 W, 5 min

Number of samples simultaneously digested: 10 vessels

Reagents: 3 mL HNO3 (2 mol/L) + 1 mL H2O2 30% (m/v)


Detection technique: TS-FF-AAS and FAAS

Analytes: Se

Evaluation of trace element contents in canned foods marketed from

Turkey

Mustafa, T. and Mustafa, S., Food Chemistry, 102 (4), 1089-1095, 2007

Abstract

Trace element contents of 10 canned foods (mushroom, corn, pea, mixed

vegetable, tomato, red mullet, stuffed grape leaves, pickle, bean,

delicatessen) from Turkish markets were determined by flame and graphite

furnace atomic absorption spectrometry after microwave digestion. The

accuracy of the method was determined by use of a standard reference

material (NIST SRM 1573a Tomato Leaves). The contents of investigated

trace elements in canned foods were found to be in the range of 2.85–7.77

µg/g for copper, 8.46–21.9 µg/g for zinc, 6.46–18.6 µg/g for manganese,

27.5–79.6 µg/g for iron, 0.05–0.35 µg/g for selenium, 0.93–3.17 µg/g for

aluminium, 0.19–0.52 µg/g for chromium, 0.18–0.75 µg/g for nickel, and

0.20–1.10 µg/g for cobalt. The results found were compared with those

reported by scientists from various countries.

Type of sample: canned foods (mushroom, corn, peas, mixed vegetable,

tomato, red mullet, stuffed grape leaves, pickle, bean)


Microwave oven (model): Ethos D microwave closed system Milestone,

Sorisole, Italy (maximum pressure 98.65 atm, maximum temperature

300 oC)

Vessel material: -



ventilation 8 min.


Reagents: 6 mL of concentrated HNO3 (65%) v/v and 2 mL of

concentrated H2O2 (30%) m/v


Detection technique: FAAS and GFAAS HGAAS

Analytes: Cu, Zn, Mn, Fe, Se, Al, Cr, Ni and Co

Focused microwaves-assisted extraction and simultaneous

spectrophotometric determination of vanillin and p-hydroxy

benzaldehyde from vanilla fragans

Patrón, A. L. and Macías, M. P. C., Talanta, 69 (5), 882-887, 2006

Abstract

A new method to quick extraction of vanillin and p-hydroxybenzaldheyde

(PHB) of vanilla beans from vanilla fragans is proposed. Samples were

irradiated with microwaves energy to accelerate the extraction process and

photometric monitoring was performed at 348 and 329 nm (vanillin and

PHB, respectively). The simultaneous determination of vanillin and PHB

from extracts was performed using the Vierordt’s method, which showed a

precision, expressed as relative standard deviation, smaller 2.5% for both

analytes. Conditions such as microwaves irradiation power, number of

irradiation and non-irradiation cycles, irradiation time and ethanol

concentration were optimized by means of multivariate screening that

showed that irradiation power and number of irradiation cycles are the most

significant condition in the vanilla extraction process. The focused

microwave-assisted extraction (FMAE) was applied to commercial (dried

vanilla beans from fresh green vanilla beans), lyophilised and dried

(commercial vanilla dried at 135 °C in oven) vanilla beans samples. The

results showed that the extraction of vanillin and PHB in the commercial

vanilla samples were higher than in dried and lyophilised samples. With the

proposed FMAE a decrease in the extraction time of 62 times and an

increase in the vanillin and PHB concentrations between 40 and 50% with

respect to the official Mexican extraction method, were obtained.

Type of sample: vanilla beans

Sample amount: 1 g

Microwave oven (model): Microdigest 301 (Prolabo, France)


Heating: twenty cycles of 1 min of irradiation at 150 W, each one with a

delay time between 3 min.


Reagents: 25 mL of ethanol 70%

Pretreatment general aspects: 2 procedures were employed: dried the

sample in an oven at 135 ºC and lyophilization.

Detection technique: spectrophotometry

Analytes: vanillin and p-hydroxybenzaldehyde

High-performance ion chromatography assessment of inorganic and

organic nitrogen fractions in potatoes

Prusisz, B., Jaskiewicz, L. and Pohl, P., Microchimica Acta, 156 (3-4),

219-223, 2006

Abstract

A new high-performance ion chromatography assay for organic and

inorganic nitrogen analysis has been proposed and examined. In the

devised protocol, inorganic sample constituents were measured after

ultrasonically assisted water extraction. The amine and amide nitrogen

content was assessed after modified Kjeldahl digestion and determined as

NH4, and the total nitrogen content was quantified as NO3 after microwave-

facilitated digestion. Finally, the nitro, azo, azoxy nitrogen was calculated

by comparison of the total nitrogen content and all measured nitrogen

species. The detection limits of the measured ions were 2.0, 0.82 and 0.17

mg/L for nitrate, nitrite and ammonium, respectively. For samples of

potatoes, the average shares of the nitrogen species found in the total

nitrogen content were: 0.83% of nitrate nitrogen, <0.03% of nitrite

nitrogen, 2.1% of ammonium nitrogen, 71% of nitro, azo, azoxy nitrogen,

and 26% of amine, amide nitrogen. We expect the method to be applicable

to different vegetable samples. The quality of the results obtained was

verified by analyzing certified reference material and comparing to another

analytical method.

Type of sample: potatoes


Microwave oven (model): MLS 1200 Mega (Milestone, Sorisole, Italy)

with a microwave digestion rotor (MDR-1000/6/100/110)


Heating: 250 W for 5 min, 0 W for 15 min, 600 W for 10 min and

ventilation for 10 min.


Reagents: 10 mL of H2O2 22% (m/v) and 50 μL of acetic acid 80% (v/v)

Pretreatment general aspects: The samples were dried at 105 °C and

ground in a agate mortar prior to analysis.

Detection technique: HPLC

Analytes: NO2-, NO3

- and NH4+

Investigation of palladium and platinum levels in food by sector field

inductively coupled plasma mass spectrometry

Frazzoli, C., Cammarone, R. and Caroli, S., Food Additives and

Contaminants, 24 (5), 546-552, 2007

Abstract

Over the last decades, there has been increased concern regarding the

impact of some noble metals, such as Pd and Pt, on human health. These

elements pollute the environment due to their widespread use as catalytic

converts and in medical applications. The risk they pose to human health

and the environment is still controversial; however, literature data point to

diet as an important source of uptake by the human body. Within this

context, the total Pd Pt content of several Italian food commodities has

been investigated. A total of 90 samples, including flour products,

vegetables and foodstuffs of animal origin (meat, milk and eggs), were

collected and freeze-dried. Samples were analyzed by sector field

inductively coupled plasma mass spectrometry (SF-ICP-MS) after

chopping or crushing followed by freeze-drying and microwave (MW)-

assisted acid digestion in a Class-100 clean-room. A mathematical

approach was adopted to correct the mass signals for still unresolved

interference (m/∆m = 300, 10000). The lowest and highest concentrations

of Pt, i. e. 17 and 93 ng/kg (dry weigth, dw), were found in vegetables and

flour products, respectively. The lowest Pd level (2830 ng/kg dw) was

found in eggs and the highest (47800 ng/kg) in vegetables.

Type of sample: vegetables and foodstuffs of animal origin (meat, milk

and eggs)


Microwave oven (model): MLS 1200 MEGA; Milestone, Bergamo, Italy


Heating: Step 1: 2 min and 250 W. Step 2: 2 min and o W. Step 3: 5 min

250 W. Step 4: 5 min and 500 (400) W. Step 5: 5 min and 650W. Step 6: 5

min and 250 W.


Reagents: 7 mL of a 1:6 mixture 30% H2O2 and 65% HNO3 (v/v)

Pretreatment general aspects: All vegetables were sampled and stored

without washing or peeling. Samples were assigned an identification code,

packed, frozen and stored at -20 oC until analysis. Prior to digestion,

aliquots of each sample were, depending on their nature, chopped or

crushed and then freeze-dried. Freeze-drying was included in the analytical

protocol to normalize the water content (70-80% for eggs and meat, 90%

for vegetables and milk and 20-40% for flour) and, thus, facilitate the

acquisition of comparable data. Moreover, the removal of water increases

the relative concentration of the analytes by a factor of 1.5-10, thus making

their determination easier. The freeze-dried samples were stored at room

temperature in a desiccator.


Analytes: Pd and Pt

Method development for the determination of manganese, cobalt and

copper in green coffee comparing direct solid sampling electrothermal

atomic absorption spectrometry and inductively coupled plasma

optical emission spectrometry

Oleszczuk, N., Castro, J. T., da Silva, M. M., Korn, M. G. A., Welz, B. and

Vale, M. G. R., Talanta, 73 (5), 862–869, 2007

Abstract

A method has been developed for the determination of cobalt, copper and

manganese in green coffee using direct solid sampling electrothermal

atomic absorption spectrometry (SS-ET AAS). The motivation for the

study was that only a few elements might be suitable to determine the

origin of green coffee so that the multi-element techniques usually applied

for this purpose might not be necessary. The three elements have been

chosen as test elements as they were found to be significant in previous

investigations. A number of botanical certified reference materials (CRM)

and pre-analyzed samples of green coffee have been used for method

validation, and inductively coupled plasma optical emission spectrometry

(ICP OES) after microwave-assisted acid digestion of the samples as

reference method. Calibration against aqueous standards could be used for

the determination of Mn and Co by SS-ET AAS, but calibration against

solid CRM was necessary for the determination of Cu. No significant

difference was found between the results obtained with the proposed

method and certified or independently determined values. The limits of

detection for Mn, Cu and Co were 0.012, 0.006 and 0.004 µg/g using

SS-ET AAS and 0.015, 0.13 and 0.10 µg/g using ICP OES. Seven samples

of Brazilian green coffee have been analyzed, and there was no significant

difference between the values obtained with SS-ET AAS and ICP OES for

Mn and Cu. ICP OES could not be used as a reference method for Co, as

essentially all values were below the limit of quantification of this

technique.

Typeof sample: Coffee


Microwave oven (model): Ethos EZ (Milestone, Sorisole, Italy)


Heating: In the first step the temperature was linearly increased to 90 ◦C in

4 min with maximum power of the magnetron of 1000 W. In the second

step the temperature was kept at 90 ◦C for 2 min. In the third step the

temperature was linearly increased to 180 ◦C in 4 min and in the fourth step

the temperature was kept at 180 ◦C for 15 min.


Reagents: 7 mL of HNO3 conc. and 1 mL of H2O2 conc.

Pretreatment general aspects: The vessels were placed in a fume hood

for 1 h for pre-digestion.


Analytes: Co, Cu and Mn

Multivariate optimization of a microwave-assisted leaching procedure

using dilute acid solutions, for FAAS determination of Cu, Fe, Mn and

Zn in multivitamin/multimineral supplements

Soriano, S., Pereira Netto, A. D. and Cassella, R. J., Analytical and

Bioanalytical Chemistry, 387 (3), 1113-1120, 2007

Abstract

This work presents the development of a methodology for the

determination of Cu, Fe, Mn and Zn in samples of

multivitamin/multimineral tablets, by flame atomic absorption

spectrometry (FAAS), after extraction of the analytes with diluted

hydrochloric acid solution. Several parameters that could influence the

extraction process such as acid extraction solution concentration and

nature, mixing mode (ultrasonic or magnetic stirring), extraction time and

sample composition were evaluated. The obtained results showed that Fe,

Mn and Zn were easily extracted with 1 mol/L HCl solution after 5 min of

mixing with either ultrasonic or magnetic stirring for all studied samples.

On the other hand, Cu extraction appeared to be more complex since it

could only be extracted at the same conditions for silicate-free samples. For

samples containing silicates the time of contact between solid sample and

extraction solution presented remarkable influence, being necessary up to

12 h to achieve quantitative recovery with 1 mol/L HCl solution. The

developed methodology was applied in the determination of Cu, Fe, Mn

and Zn in seven commercially available multivitamin/multimineral tablets.

The results obtained with the developed method were compared with those

obtained after total digestion of samples using a closed-vessel microwave

oven device.

Type of sample: multivitamin/multimineral tablets


Microwave oven (model): DGT-100 Plus microwave oven from Provecto

(Jundiaí-Brazil)


Heating: Step 1: 300 W, 2 min. Step 2: 720 W, 5 min. Step 3: 200 W,

5 min.


Reagents: 5 mL HNO3 conc.

Pretreatment general aspects: Solid multivitamin/multimineral

preparations were purchased from a local market. Prior to analysis, a set

with 20 tablets was manually ground with an agate mortar and pestle,

homogenized and sieved through a 1mm pore diameter plastic sieve.


Analytes: Cu, Fe, Mn and Zn

Multivariate technique for optimization of digestion procedure by

focussed microwave system for determination of Mn, Zn and Fe in

food samples using FAAS

Santelli, R. E., Bezerra, M. A., Santana, O. D., Cassela, R. J. and Ferreira,

S. L. C., Talanta, 68 (4), 1083-1088, 2006

Abstract

This article describes the development by response surface methodology

(RSM) of a procedure for iron, zinc and manganese determination by flame

atomic absorption spectrometry (FAAS) in food samples after digestion

employing a focussed microwave system. A Doehlert matrix was used to

find optimal conditions for the procedure through response surface study.

Three variables (irradiation power and time and composition of oxidant

solution - HNO3+H2O2) were regarded as factors in the optimization study.

The working conditions were established as a compromise between

optimum values found for each analyte taking into consideration the

robustness of the procedure. These values were 12 min, 260 W and 42%

(v/v) for irradiation time, irradiation power and percent of H2O2 in solution,

respectively. The accuracy of the optimized procedure was evaluated by

analysis of certified reference materials and by comparison with a well-

established closed vessel microwave dissolution methodology.

Type of sample: Rice flour, corn starch, oat flour, manioc flour, wheat

flour, oat flour, rice flour, wheat flour, corn starch, corn flour


Microwave oven (model): focused microwave Soxwave 100 (Prolabo,

France) and a closed vessel microwave CDS 7000 (Spex).


Heating: For the digestion by closed vessel microwave, 2 steps of 25 min,

at 1000 W were performed. The pressure was not higher than 12.24 atm

and the temperature was not higher than 190 °C. For the digestion by

focused microwave, power settings from 60 to 300 W could be applied in

steps of 10 W and the microwave energy was focussed into quartz vessel

under atmospheric pressure.

Number of samples simultaneously digested: 1 (focussed procedure) and

not informed for the closed vessel

Reagents: HNO3 and H2O2, at different concentrations

Pretreatment general aspects: the samples were dried overnight at 110 ±

5 °C


Analytes: Fe, Zn and Mn

Optimisation of microwave digestion for determination of Fe, Zn, Mn

and Cu in various legumes by flame atomic absorption Spectrometry

Erdogan, S., Erdemoglu S. B. and Kaya, S., Journal of the Science of Food

and Agriculture, 86 (2), 226-232, 2006

Abstract

Fe, Zn, Mn and Cu levels in three Turkish legumes, kidney bean

(Phaseolus vulgaris L.), lentil (Lens esculenta) and chickpea (Cicer

arietinum), were determined by flame atomic absorption spectrometry.

Dissolution conditions in the microwave-assisted wet digestion method

were studied by investigating several variables, including type of acid

mixture, acid volume, digestion time, microwave power input and sample

weight. Comparison with conventional wet acid digestion was also made.

In order to check the element losses during digestion and the accuracy of

the results, all tests were repeated after the addition of a spiked standard

element solution to the legume sample. The microwave-assisted digestion

procedure optimised for kidney bean was adapted for lentil and chickpea.

Fe, Zn, Mn and Cu concentrations (mg per 100 g sample) were determined

in kidney bean as 6.27 ± 0.94, 2.23 ± 0.36, 1.64 ± 0.14 and 0.99 ± 0.19, in

lentil as 8.24 ± 1.11, 2.46 ± 0.06, 1.17 ± 0.19 and 1.01 ± 0.28 and in

chickpea as 6.00 ± 1.40, 2.21 ± 0.14, 1.60 ± 0.43 and 0.58 ± 0.18

respectively.

Type of sample: Kidney beans, lentils and chickpeas samples of several

varieties.

Sample amount: 1 g

Microwave oven (model): An Arcelik 1500 W microwave oven and a

HP-500 MARS 5 (CEM Corporation, Matthews, NC, USA).


Heating: different digestion programs were evaluable. Digestion time

between 4-10 min and microwave power ranging from 150-300 W.


Reagents: 4 mL HNO3 conc. and 4 mL H2O2 30% (v/v)

Pretreatment general aspects: samples were ground in a agate mortar


Analytes: Fe, Zn, Mn, Cu

Factorial design employed for microwave-assisted digestion of beans

samples

Costa, L. M., Korn, M. G. A., Castro, J. T., Santos, W. P. C., Carvalho, E.

V. and Nogueira, A. R. A., Química Nova, 29 (1), 149-152, 2006

Abstract

Factorial design employed for microwave-assisted digestion of bean

samples. The use of factorial design was evaluated for optimization of

focused microwave-assisted digestion of bean samples. Calcium, Fe, Mg,

Mn and Zn percentual recoveries were determined in digestates after

focused-microwave-assisted digestion according to factorial design

procedures. A cavity microwave digestion was carried out to certify the

elemental compositions obtained. The accuracy was checked using a

standard reference material, the NIST SRM 8433 - Corn Bran. Results are

in agreement with certified values at the 95% confidence limit when the

Student t-test was used. Volumes of nitric and sulfuric acid, temperature,

and the interplay between HNO3 and H2SO4 initial volumes were

significant variables according to P-values in the analysis of variance

(ANOVA).

Type of sample: beans

Sample amount: 0.5 g (when STAR 6 was used) and 0.2 g (when

Multiwave was used)

Microwave oven (model): STAR 2 (CEM Corporation, Matthews, NC,

USA) and Multiwave (Anton Paar, Graz, Austria)

Vessel material: Teflon (when Multiwave was used) and for digestion

using STAR 6

Heating: Procedure with Multiwave microwave: 400 W for 3 min, 850 W

for 6 min and 1000 W for 10 min.

Procedure with STAR 6 microwave: Initial addition of 4-7 mL of HNO3

and 1-3 mL of H2SO4. Addition of 1 mL of HNO3 and 2 min at 95 ºC; 1 mL

of HNO3 and 2 min at 150 ºC; 3 min at 170-200 ºC and 3 min at 170-

200 ºC.

Number of samples simultaneously digested: 6 (for digestion using

Multiwave microwave) and for digestion using STAR 6, the number of

simultaneous treated samples was not informed.

Reagents: 2 mL of HNO3 conc. and 1 mL of H2O2 30% (m/v) when

digestion was performed in Multiwave and for digestion using STAR 6,

HNO3 conc. and H2SO4 conc. were used.



Analytes: Ca, Fe, Mg, Mn and Zn

Preliminary chemometric study of minerals and trace elements in

Spanish infant formulae

Larrañaga, S. C. and Blasco, N. I., Analytica Chimica Acta, 555 (2), 354-

363, 2006

Abstract

The concentrations of minerals (Na, K, P, Ca and Mg) and trace elements

(Fe, Zn, Cu, Mn, Se, Al, Cd and Pb) in a total of 105 different infant

formulae (starter, follow-up, premature, specialised and soya formulae)

marketed in Spain were determined by atomic spectrometry (flame and

electrothermal) and inductively coupled plasma emission spectroscopy

after acid-microwave decomposition. On the basis of the elements

distribution, a preliminary chemometric study with the use of pattern

recognition methods was carried out. Hierarchical cluster analysis (HCA),

principal component analysis (PCA), as unsupervised exploratory

techniques, and linear discriminant analysis (LDA), were applied to

characterise, classify and distinguish the different types of infant formulae.

The HCA results showed that mineral and trace element content data

support adequate information to obtain the infant formula differentiation.

PCA permitted the reduction of 13 variables to four principal components

accounting for 61.9% of the total variability. This four-factor model

interprets reasonably well the correlations of these studied elements. The

obtained element associations may be attributed to the composition of

matrix ingredients, the contamination during elaboration, the additives and

mineral supplements added and the present tendency of standardization in

the manufacture of infant formulae. The application of LDA gave a 77.1%

of infant formulae correctly assigned with three clearly differentiated and

two overlapped groups. The use of discriminant functions, as a

complementary tool, to distinguish the different types depending on protein

matrix of infant formula, is also discussed. This survey shows that HCA,

PCA and LDA techniques appear useful tools for the characterisation and

classification of infant formulae using their elemental profile.

Type of sample: infant formulae

Sample amount: 0.3-0.4 g or 3 mL

Microwave oven (model): Ethos Plus (Milestone, Sorisole, Italy)


Heating: 25-170 °C for 10 min and 170 °C for 10 min, both at 1000 W,

followed immediately by ventilation at room temperature (20 min)


Reagents: 7 mL of HNO3 conc.


Detection technique: FAAS, ET AAS and ICP-AES

Analytes: Al, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, P, Pb, Se, and Zn

Sample treatment procedures for the determination of mineral

constituents in honey by inductively coupled plasma optical emission

spectrometry

Mendes, T. M. F. F., Baccan, N. and Cadore, S., Journal of the Brazilian

Chemical Society, 17 (1), 168-176, 2006

Abstract

Preparative methods for quantification of inorganic constituents in honey

by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES)

using microwave assisted digestion and ultrasonication procedures were

developed. Analytical aspects such as matrix complexity, instrumental

optimization and the essentiality/toxicity of the species K, Ca, Mg, Na, Fe,

Mn, Zn, Cu, Co, Ni, Pb, Cd were considered. Parameters such as plasma

power, nebulizer flow rate, torch configuration and the convenience of the

use of yttrium as internal standard were evaluated. Recoveries between 93

and 107% (microwave digestion) and between 90 to 110% (ultrasonication

procedure) and relative standard deviations lower than 10% were obtained.

Samples of Brazilian honeys, from different parts of the country, were

analysed and the results obtained provide relevant information about their

mineral content.


Sample amount: 1 g

Microwave oven (model): DGT 100, Provecto, Brazil


Heating: 1 min at 320 W, 2 min at 0 W, 5 min at 320 W, 5 min at 520 W

and 5 min at 740 W


Reagents: 2 mL HNO3 conc. and 2 mL H2O2 (30%, v/v)

Pretreatment general aspects: 0.5 mL of Y (100 mg/L) solution was used

as internal standard


Analytes: Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Ni, Pb and Zn

Simultaneous determination of arsenic, selenium and mercury in

foodstuffs by chemical vapour generation inductively coupled plasma

optical emission spectroscopy

Grotti, M., Lagomarsino, C. and Magi, E., Annali di Chimica, 96 (11-12),

751-764, 2006

Abstract

A procedure for the simultaneous determination of arsenic, selenium and

mercury in foodstuffs has been developed. After a two-step microwave-

assisted wet digestion in closed vessels, using concentrated nitric acid and

hydrogen peroxide, the solution was analysed by inductively coupled

plasma multichannel-based emission spectrometry using chemical vapour

generation as the sample introduction system. All steps of the procedure,

such as solid sample dissolution, pre-reduction to the suitable oxidation

state, vapor generation, transport and atomization have been designed and

optimised taking into account the concomitant presence of all the analytes

considered. Temporal variation of analytical signals as well as interfering

effects due to transition elements were also studied. Under the optimised

operating conditions, the achieved detection limits for the simultaneous

determination of arsenic, selenium and mercury in foodstuffs were 0.006,

0.023 and 0.018 μg/g, respectively, allowing their determination in real

samples. Precision of the analytical procedure was 6.8% for arsenic, 5.2%

for selenium and 7.7% for mercury (n = 7). The accuracy and reliability of

the method was verified by the analysis of both standard reference

materials (rice flour and spinach leaves) and real samples (natural and Se

enriched rice).

Type of sample: rice



USA)


Heating: Step 1: 5 mL of HNO3 concentrated were added and the

following program was performed: a) 5 min with a control pressure of

5.44 atm and 50% power; b) 5 min with a control pressure of 8.16 atm and

70% power; c) 10 min with a control pressure of 12.02 atm and 100%

power. After cooling, 2 mL of 30% H2O2 (m/v) were added and the sample

treated for 10 min with a control pressure of 5.44 atm, using 100% power.

A temperature control at 200°C was also applied.


Reagents: 5 mL HNO3 concentred + 2 mL H2O2 30% (v/v)


Detection technique: CVG-ICP-OES

Analytes: As, Se and Hg

Study of the bioavailability of selenium in cows’ milk after a

supplementation of cow feed with different forms of selenium

Muñiz-Naveiro, O., Domínguez-González, O. Bermejo-Barrera, A.,

Bermejo-Barrera, P., Cocho, J. A. and Fraga, J. M., Analytical and


Abstract

The purpose of the work described in this paper was to develop an easy and

quick in-vitro method for comparing the bioavailability of selenium in

cows’ milk after different cow feed. The study focuses on bioavailability

differences resulting from the use of different selenium species (organic

selenium as selenised yeast and sodium selenite) for supplementation of

forage. A procedure for determination of selenium in cows’ milk and

dialysates, by hydride-generation atomic-fluorescence spectrometry

(HG-AFS) after microwave-assisted acid digestion, was optimised. The

results show it is possible to obtain cows’ milk enriched with selenium at

different concentration without altering the original composition of the

milk. The bioavailability was statistically greater for cows’ milk obtained

after supplementation of forage with organic selenium at levels of 0.4 and

0.5 μg/g Se than for that obtained after supplementation with inorganic and

organic selenium at levels of 0.2 and 0.3 μg/g Se.

Type of sample: cows’ milk


Microwave oven (model): Ethos Plus (Milestone Corporation, Sorisole,

Italy)


Heating: In the first step the vessel was heated to 200 °C for 10 min in the

microwave oven; and, in the second step the vessel was heated again in the

microwave oven to 130 °C for 10 min.


Reagents: Step 1: 2.0 mL HNO3 (70% v/v) + 1.0 mL H2O2 (35% m/v), 2.5

mL H2O. Step 2: 1.4 mL HCl (37% v/v). Step 3) 0.4 mL urea solution

(50% m/v)


Detection technique: HG-AFS

Analytes: Se

Study on the simultaneous determination of some essential and toxic

trace elements in honey by multi-element graphite furnace atomic


Ajtony, Z., Bencs, L., Haraszi, R., Szigeti, J. and Szoboszlai, N., Talanta,

71 (2), 683–690, 2007

Abstract

A multi-element graphite furnace atomic absorption spectrometry

(GFAAS) method was elaborated and applied for the simultaneous

determination of As, Cd, Cr, Cu, and Pb in various kinds of honey samples

(acacia, floral, linden, rape, and milkweed) using the transversally heated

graphite atomiser (THGA) with end-capped tubes and integrated graphite

platforms (IGPs). For comparative GFAAS analysis, direct (without

digestion) and indirect (with digestion in a microwave oven) sample

preparation procedures were tested. The effects of several chemical

modifiers, such as NH4H2PO4, NH4H2PO4–Mg(NO3)2, and Pd(NO3)2–

Mg(NO3)2, were studied to obtain optimal pyrolysis and atomization

conditions for the set of analytes studied. The most efficient modifier was

proved to be the mixture of 5 µg Pd (applied as nitrate) plus 3 µg

Mg(NO3)2, allowing the optimal 600 ◦C pyrolysis and 2300 ◦C atomization

temperatures. To prevent the sputtering and foaming of the matrix during

the drying and pyrolysis steps of the furnace heating program, the sample

and modifier solutions (20 + 5 µL, respectively) were dispensed together

onto the IGP of the THGA pre-heated at 80 ◦C. The effect of increasing

concentration of honey matrix was studied on the integrated absorbance

(Aint) signals of analytes. The Aint signals of Cr and Pb were not altered up

to 10% (m/v) matrix content in the sample solutions. The matrix effect was

slightly suppressive on the Aint signals of As, Cd, and Cu above 2% (m/v)

honey concentration. The recovery was found to be ranged between 85 and

115% for Cd, Cr, Cu, and Pb, whereas it was a lower, compromise value of

70–99% for As. The limit of detection (LOD) data were 1, 0.04, 0.09, 0.3,

and 0.6 µg/L for As, Cd, Cr, Cu, and Pb, respectively, which values

correspond to 20, 0.8, 1.8, 5.3, and 12 ng/g, respectively, in the solid

samples. The characteristic masses were found to be 21 pg As, 1.3 pg Cd, 4

pg Cr, 12 pg Cu, and 33 pg Pb. The As, Cd, Cr, Cu, and Pb contents of the

studied 42 honey samples varied significantly, i.e. from below the LOD up

to 13, 3.3, 109, 445, and 163 ng/g, respectively.



Microwave oven (model): MW-oven (MLS 1200 Mega, Milestone, Italy)

Vessel material: tetrafluormethaxil (TFM)

Heating: The MW-oven program consisted of five steps: 1) 250 W for

1 min. 2) 0 W for 2 min. 3) 250 W for 5 min. 4) 400 W for 5 min. 5) 500 W

for 5 min.


Reagents: 5 mL HNO3 conc. and 1 mL H2O2 conc.



Analytes: As, Cd, Cr, Cu, and Pb

Trace element levels in honeys from different regions of Turkey

Tuzen, M., Silici, S., Mendil, D. and Soylak, M., Food Chemistry, 103 (2),

325-330, 2007.

Abstract

A survey of 25 honey samples from different botanical origin, collected all

over the Turkey was conducted to assess their trace element contents. The

aim of this study was to determine the levels of cadmium (Cd), lead (Pb),

iron (Fe), manganese (Mn), copper (Cu), nickel (Ni), chromium (Cr), zinc

(Zn), aluminium (Al) and selenium (Se) in honey samples from different

regions of Turkey. Trace element contents were determined by a flame and

graphite furnace atomic absorption spectrometry technique after dry-

ashing, microwave digestion and wet-digestion. The accuracy of the

method was corrected by the standard reference material, NIST-SRM 1515

Apple leaves. The contents of trace elements in honey samples were in the

range of 0.23–2.41 µg/g, 0.32–4.56 µg/g, 1.1–12.7 µg/g, 1.8–10.2 µg/g,

8.4–105.8 µg/kg, 2.6–29.9 µg/kg, 2.4–37.9 µg/kg, 0.9–17.9 µg/kg, 83–325

µg/kg and 38–113 µg/kg for Cu, Mn, Zn, Fe, Pb, Ni, Cr, Cd, Al and Se,

respectively. Iron was the most abundant element while cadmium was the

lowest element in the Turkish honeys surveyed. The results showed that

trace element concentrations in the honeys from different regions were

generally correlated with the degree of trace element contamination of the

environment.



Microwave oven (model): Milestone Ethos D closed vessel microwave

digestion system (maximum pressure 98.65 atm, maximum temperature

300 oC).




ventilation 8 min.


Reagents: 3 mL of HNO3 (65%) v/v and 1 mL of H2O2 (30%) m/v


Detection technique: FAAS and GFAAS equipped with HGA

Analytes: Cu, Mn, Zn, Fe, Pb, Ni, Cr, Cd, Al and Se.

Determination of vanadium in human hair slurries by electrothermal

atomic absorption spectrometry

Fernandes, K. G., Nogueira, A. R. A., Gomes Neto, J. A. and Nóbrega, J.

A., Talanta, 71 (3) 1118–1123, 2007

Abstract

This work describes an analytical procedure for vanadium determination in

human hair slurries by electrothermal AAS using longitudinal heating

(LHGA) and transversal heating (THGA) graphite furnace atomizers. The

samples were powdered using cryogenic grinding and the hair slurries

containing 0.2% (m/v) were prepared in three different media for

determination of vanadium: 0.14 mol/L HNO3, 0.1% (v/v) Triton X-100

and 0.1% (v/v) water soluble tertiary amines (CFA-C, pH 8). The limits of

detection (LOD), limits of quantification (LOQ), and characteristic masses

obtained were 0.28, 0.95 g/L and 35 pg (LHGA) and 0.34, 1.13 g/L and 78

pg (THGA), respectively. The accuracy of the analytical results obtained

by the proposed procedure in both equipments was confirmed by a paired

t-test at the 95% confidence level and compared with a conventional

procedure based on acid digestion.

Type of sample: human hair

Sample amount: 0.8 g approx.

Microwave oven model: Milestone Ethos 1600 (Sorisole, Italy)

Vial material: PFA

Heating: Step 1: 250 W, 120 s. Step 2: 0 W, 90 s. Step 3: 550 W, 120 s.

Step 4: 600 W, 180 s. Step 5: 700 W, 180 s. Step 6: ventilation, 0 W and

300 s.


Reagents: 2.0 mL of 50 % (v/v) HNO3 + 1.0 mL of 30 % (m/m) H2O2



Analytes: V

Determination of Ge, As and Se in nickel-based alloys by flow injection

hydride generation dynamic reaction cell inductively coupled plasma

mass spectrometry

Chen, Z. C. and Jiang, S. J., Journal of Analytical Atomic Spectrometry, 21

(6), 566-573, 2006

Abstract

A dynamic reaction cellt inductively coupled plasma mass spectrometry

(DRC-ICP-MS) method has been developed for the determination of Ge,

As and Se in nickel-based alloys using flow injection hydride generation as

the sample introduction system. The hydride generation technique

alleviated the matrix-based interferences, such as 58Ni16O+, 59Co16O+ and 62Ni16O+, on the determination of 74Ge+, 75As+ and 78Se+. L-Cysteine is used

as a masking agent to reduce the interferences arising from the transition

metals. By using H2 as the reactive cell gas in the DRC, the interferences

arising due to the formation of 35Cl37Cl+, 37Cl37Cl+, 40Ar35Cl+ and 38Ar40Ar+

on the determination of 72Ge+, 74Ge+, 75As+ and 78Se+ have also been

alleviated. The effects of the operating conditions of the hydride generation

and DRC system have been studied to select the best signal-to-background

ratio (S/B). Validation of the method is carried out by determining Ge, As

and Se in standard reference materials of nickel-based alloys (NIST SRM

897–899). The concentrations of Ge, As and Se have been determined by

standard addition and/or isotope dilution methods. The Se experimental

results agreed satisfactorily with the certified values, and that of Ge and As

with reference values obtained by pneumatic nebulization using high

resolution ICP-MS. The detection limits for Ge, As and Se were in the

range 0.001, 0.001 and 0.02 ng ml-1, respectively, which corresponds to

1–20 ng/g in the original alloy samples. The precision between sample

replicates was better than 6% for all the determinations.

Type of sample: nickel-based alloy reference samples


Microwave oven (model): MARS 5 microwave digester (CEM

Corporation, Matthews, NC, USA)


Heating: The microwave power was set at 70%, and the samples were

heated for 45 min. After removing the excess acid by heating the solution

to dryness, the final residue was diluted to 25 mL with 10% HCl.


Reagents: 1 mL HNO3 + 3 mL HCl 10% (v/v)


Detection technique: DRC-ICP-MS

Analytes: Ge, As and Se

Determination of major, minor and trace elements in cobalt-

substituted lithium nickelate ceramic powders by inductively coupled

plasma optical emission spectrometry

Mosqueda, Y., Pomares, M., Pérez-Cappe, E. L., Miranda, A., Fariñas, J.

C., and Larrea, M. T., Analytical and Bionalytical Chemistry, 386 (6),

1855-1862, 2006

Abstract

An analytical method was developed for the determination of three major

(Li, Ni and Co) and fourteen minor or trace elements (Al, Ba, Ca, Cu, Cr,

Fe, K, Mg, Mn, Na, Si, Sr, Ti and V) in LiNi1−xCoxO2 (x=0.2–0.8) ceramic

powders by inductively coupled plasma optical emission spectrometry.

Sample dissolution was achieved by 25% nitric acid digestion in a

microwave oven. For each element, an analytical line free from spectral

interferences was selected. A detailed study of matrix effects over a wide

interval of total excitation energy (TEE) lines (1.62–16.50 eV) was

performed at near-robust plasma conditions. A remarkable enhancement in

atomic lines with TEE < 4 eV was noticed, whereas a significant reduction

in atomic and ionic lines with TEE > 4 eV was observed. The extrapolation

to infinite dilution method was successfully used to overcome these

nonspectroscopic interferences. Detection limits (3σ) varied from

0.21 mg/ kg for Sr to 49.7 mg/kg for Na. The precision of determination

(obtained as the relative standard deviation) was lower than 1% for the

major elements Li, Ni and Co and between 0.69 and 10% for minor and

trace elements. The accuracy of the method ranged from 91 to 101% for

major elements, and from 90 to 110%, or close to this range, for most of

the impurities in both of the samples studied.

Type of sample: ceramic powder


Microwave oven (model): Ethos 1600 microwave labstation (Milestone

Corporation, Sorisole, Italy)

Vessel material: TFM Teflon

Heating: Step 1: 2 min, 120 °C and 500 W. Step 2: 1 min, 100 °C and 0 W.

Step 3: 3 min, 160 °C and 500 W. Step 4: 2 min, 180 °C and 500 W. Step

5: 1 min, 160 °C and 0 W. Step 6: 6 min, 180 °C and 500W


Reagents: 5 mL HNO3 (25% v/v)

Pretreatment general aspects: Sample were homogenized and dried


Analytes: Li, Ni, Co, Al, Ba, Ca, Cu, Cr, Fe, K, Mg, Mn, Na, Si, Sr, Ti and

V

Direct determination of trace elements in high purity gallium by high

resolution inductively coupled plasma mass spectrometry

Hualin, X., Xidu, N., and Yougen, T., Chinese Journal of Analytical

Chemistry, 34 (11), 1570-1574, 2006

Abstract

An analytical method using high resolution inductively coupled plasma

mass spectrometry (HR-ICP-MS) for rapid simultaneous determination of

Be, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As, Mo, Ag, Cd, In,

Sb, Ba, Pb, and Bi elements in high purity gallium was described. The

sample was dissolved in HNO3 and HCl by microwave digestion, then the

above 22 elements in the solution were detected directly by HR-ICP-MS.

Most of the spectral interferences could be avoided by measuring in the

high resolution mode (HRM). The matrix effects because of the presence of

excess HCl and Ga were evaluated. Correction for matrix effects was made

using Sc, Rh and Tl as internal standards. The conditions of the

determination were optimized and discussed. The result showed that the

detection limit of the method was in the range of 0.001–0.21 μg/L, the

relative standard deviation (RSD) was less than 3.3% and the recovery of

the samples was in the range of 89.8%–111.6%.

Type of sample: high purity gallium


Microwave oven (model): MDS-81D (CEM Corporation, Matthews, NC,

USA)


Heating: Step 1: power of 300 W;, slope temperature for 5 min; pressure

of 20.41 atm the controlled temperature at 180 °C for 5 min. Step 2: power

of 300 W; slope temperature for 20 min; pressure of 40.82 atm; the

controlled temperature at 21 °C for 10 min. On cooling at room

temperature the vessels were opened, the mixtures were filtered and then

diluted to 100 ml with 2% HNO3.


Reagents: 1 mL HNO3 + 4 mL HF + 3 mL HCl


Detection technique: HR-ICP-MS

Analytes: Be, Mg, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As, Mo,

Ag, Cd, In, Sb, Ba, Pb, and Bi.

Determination of trace impurities in high-purity zirconium dioxide by

inductively coupled plasma atomic emission spectrometry using

microwave-assisted digestion and wavelet transform-based correction

procedure

Ma, X. and Li, Y., Analytica Chimica Acta, 579 (1), 47-52, 2006

Abstract

This paper describes a rapid, accurate and precise method for the

determination of trace Fe, Hf, Mn, Na, Si and Ti in high-purity zirconium

dioxide (ZrO2) powders by inductively coupled plasma atomic emission

spectrometry (ICP-AES). The samples were dissolved by a microwave-

assisted digestion system. Four different digestion programs with various

reagents were tested. It was found that using a mixture of sulfuric acid

(H2SO4) and ammonium sulfate ((NH4)2SO4), the total sample dissolution

time was 30 min, much shorter than that required for conventional

digestion in an opening system. The determination of almost all of the

target analytes suffered from spectral interferences, since Zr shows a line-

rich atomic emission spectrometry. The wavelet transform (WT), a recently

developed mathematical technique was applied to the correction of spectral

interference, and more accurate and precise results were obtained,

compared with traditional off-peak background correction procedure.

Experimental work revealed that a high Zr concentration would result in a

significant decrease in peak height of the analyte lines, which was corrected

by standard addition method. The performance of the developed method

was evaluated by using synthetic samples. The recoveries were in the range

of 87–112% and relative standard deviation was within 1.1–3.4%. The

detection limits (3σ) for Fe, Hf, Mn, Na, Si and Ti were found to be 1.2,

13.3, 1.0, 4.5, 5.8 and 2.0 µg/g, respectively. The results showed that with

the microwave-assisted digestion and the WT correction, the detection

limits have improved by a factor of about 5 for Fe, 4 for Mn and Ti, 3 for

Si, and 2 for Hf and Na, respectively, in comparison with conventional

open-system digestion and off-peak correction. The proposed technique

was applied to the analysis of trace elements above-mentioned in three

types of ZrO2 powders.

Type of sample: high-purity zirconium dioxide


Microwave oven (model): MDS 81D microwave digestion system, CEM

Corporation, Matthews, NC, USA


Heating: 10 min at 315 W and 20 min at 630 W.


Reagents: 4 g (NH4)2SO4 + 10 mL H2SO4 conc.



Analytes: Fe, Hf, Mn, Na, Si and Ti

Determination of trace impurities in tantalum powder and its

compounds by inductively coupled plasma optical emission

spectrometry using solvent extraction

Anil, G., Reddy, M. R. P. and Prakash, T. L., Journal of Analytical

Chemistry, 61 (7), 641-643, 2006

Abstract

A procedure was developed for the analysis of 18 trace impurity elements

in capacitor-grade tantalum powder (Ta), potassium tantalum fluoride

(K2TaF7), and tantalum pentoxide (Ta2O5) using inductively coupled

plasma optical emission spectrometry (ICP-OES). The detection limits

achieved were in the ppb levels. The samples were dissolved in

hydrofluoric acid (HF) in a microwave digestion system and the Ta matrix

was extracted using cyclohexanone. The impurity traces remained almost

completely in the aqueous phase.

Type of sample: tantalum powder, potassium tantalum fluoride and

tantalum pentoxide.

Sample amount: 1 g

Microwave oven (model): MLS-1200 (Milestone Corporation, Sorisole,

Italy)


Heating: 5 min at 300 W, 5 min at 600 W and 10 min for cooling.


Reagents: HF for digestion in the microwave oven and cyclohexanone for

the analytes extraction.



Analytes: Fe, Cr, Ni, Ti, Nb, Al, Ca, Cu, Mn, Co, Mg, B, P, S, Zr, Mo, W,

and Si.

Optimized microwave-assisted decomposition method for

multi-element analysis of glass standard reference material and

ancient glass specimens by inductively coupled plasma atomic emission

spectrometry

Zachariadis, G., Dimitrakoudi, E., Anthemidis, A. and Stratis, J., Talanta,

68 (5), 1448-1456, 2006

Abstract

A novel microwave-assisted wet-acid decomposition method for the multi-

element analysis of glass samples using inductively coupled plasma atomic

emission spectrometry (ICP-AES) was developed and optimized. The SRM

621 standard reference glass material was used for this purpose, because it

has similar composition with either archaeological glass specimens or

common modern glasses. For the main constituents of SRM 621 (Ca, Na,

Al, Fe, Mg, Ba and Ti), quality control data are given for all the examined

procedures. The chemical and instrumental parameters of the method were

thoroughly optimized. Thirteen acid mixtures of hydrochloric, nitric, and

hydrofluoric acids in relation to two different microwave programs were

examined in order to establish the most efficient protocol for the

determination of metals in glass matrix. For both microwave programs, an

intermediate step was employed with addition of H3BO3 in order to

compensate the effect of HF, which was used in all protocols. The

suitability of the investigated protocols was evaluated for major (Ca, Na,

Al), and minor (Fe, Mg, Ba, Ti, Mn, Cu, Sb, Co, Pb) glass constituents.

The analytes were determined using multi-element matrix matched

standard solutions. The analytical data matrix was processed

chemometrically in order to evaluate the examined protocols in terms of

their accuracy, precision and sensitivity, and eventually select the most

efficient method for ancient glass. ICP-AES parameters such as spectral

line, RF power and sample flow rate were optimized using the proposed

protocol. Finally, the optimum method was successfully applied to the

analysis of a number of ancient glass fragments.

Type of sample: glass


Microwave oven (model): Mars 5, 1200 W (CEM Corporation, Matthews,

NC, USA)




Reagents: various acid mixtures of concentrated HNO3, HCl and HF


Detection technique: ICP-AES

Analytes: Al, Fe, Ca, Mg, Ti, Ba, Na, Mn, Sb, Cu, Co, and Pb

A new demountable hydrofluoric acid resistant triple mode sample

introduction system for ICP-AES and ICP-MS

Asfaw, A. and Wibetoe, G., Journal of Analytical Atomic Spectrometry, 22

(2), 158-163, 2007

Abstract

A new sample introduction system with a triple mode function was

developed by modifying a commercially available cyclonic spray chamber

and combining it with a commercial parallel path nebulizer. The system

can be used for nebulization only, vapor generation (hydride or cold vapor)

only and both together (dual mode). The introduction system is very

practical in use, as it can be dismantled from the bottom side and all the

inserts can be removed and cleaned easily after the end of analysis. Unlike

another commercial multimode system, this new one is HF-resistant and

can be used with all acids. The analytical performance of the new HF-

resistant triple mode sample introduction system (HFR-TMSIS) was

studied by coupling it with ICP-AES and ICP-MS and comparing the

performance with the conventional single mode HF-resistant sample

introduction systems: i.e. a V-groove nebulizer with Sturman-Masters

spray chamber for ICPAES and cross flow nebulizer with double pass

spray chamber for ICP-MS. The performance of the new system was

studied using the various modes, determining As, Cd, Cu, Fe, Mn and Pb

using ICP-AES and Cd, Cu, Hg and Pb using ICP-MS. In the first case

NaBH4 was used for hydride generation (of As), and in the second case

SnCl2 was used for generation of cold vapor (Hg). For both ICP-AES and

ICP-MS, the use of HFR-TMSIS improved the analytical performance of

both As and Hg in hydride and cold vapor generation mode, respectively,

and also in the dual mode compared to the conventional single mode

systems. For the other elements the figure of merits of nebulization and

dual mode were comparable with the conventional systems. Cold vapor

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generation mode (for the determination of Hg) and dual mode (for

simultaneous determination of cold vapor of Hg together with other

elements) were used for the analysis of various CRMs (digested with HF +

HNO3 + H2O2 or HNO3 + H2O2) by ICP-MS.

Type of sample: soil and urban particulate matter; pine needles and human

hair

Sample amount: soil and urban particulate matter: 0.2 g, pine needles and

human hair: 0.2-0.25 g

Microwave oven (model): ETHOS 1600 from Milestone (Sorisole, Italy)

with HPR-1000/10 S rotor.

Vessel material: PFA Teflon

Heating: soil and urban particulate matter: the temperature of the vessels

was increased linearly from 25 to 210 °C for 10 min and kept at 210 °C for

20 min.

pine needles and human hair: the temperature of the vessels was increased

linearly from 25 to 200 °C for 10 min and kept at 200 °C for 20 min.


Reagents: soil and urban particulate matter: 7 mL HNO3 65% (v/v) +

4 mL HF 40% (v/v) + 2 mL H2O2 30% (m/v)

pine needles and human hair: 1.75 mL HNO3 65% (v/v) + 1,25 mL H2O2

(v/v) 30% + 5 mL H2O (m/v)



Analytes: As, Cd, Cu, Fe, Mn and Pb by ICP OES. Cd, Cu, Hg and Pb by

ICP-MS

Application of microwave induced combustion in closed vessels for

carbon black-containing elastomers decomposition

Moraes, D. P., Mesko, M. F., Mello, P. A., Paniz, J. N. G., Dressler, V. L.,

Knapp, G. and Flores, E. M. M., Spectrochimica Acta Part B, 62 (9), 1065-

1071, 2007

Abstract

A rapid digestion procedure for the determination of Al, Fe, Mn, Sr and Zn

in carbon black-containing elastomers (30%) has been developed using

sample combustion in closed quartz vessels. Microwave radiation was used

for ignition. Combustion takes place in the presence of oxygen under

pressure using ammonium nitrate (50 μL of 6 mol/L) as aid for ignition.

Samples of nitrile-butadiene rubber and ethylenepropylene-diene monomer

were decomposed. A quartz device was used simultaneously as a sample

holder and for the protection of vessel cap. The influence of the absorption

solution (nitric acid or water) and the necessity of an additional reflux step

were evaluated. Determination of Al, Fe, Mn, Sr and Zn was performed by

inductively coupled plasma optical emission spectrometry. A reference

method (ASTM D 4004-06) based on conventional dry ashing and flame

atomic absorption spectrometry was used for comparison (Mn and Zn).

Results were also compared to those obtained by using wet acid digestion

in closed systems. Concentrated and diluted (4 mol/L) nitric acid, with 5

min of reflux after the combustion, gave best recoveries for all analytes

(from 97 to 101%). For dry ashing quantitative recoveries were found only

for Zn whereas for Al, Fe, Mn and Sr the recoveries were only 14, 37, 72

and 37%, respectively. With the proposed procedure the residual carbon

content was below 0.5% and further determination of analytes was feasible

with only the combustion step (for Fe a reflux with diluted HNO3 was

necessary). Complete sample digestion is obtained in less time using the

proposed procedure than with other procedures and no concentrated acids

were necessary.

Type of sample: rubber (carbon black-containing elastomers)


Microwave oven (model): Model Multiwave 3000 (Anton Paar, Graz,

Austria)


Heating: Step 1: 60 s at 1400 W. Step 2: 5 min at 1400 W (optional step).

Step 3: 20 min at 0 W


Reagents: Absorbing solution: 6 mL of water, 2, 4 or 14 mol/L HNO3,

50 μL of 6 mol/L NH4NO3

Pretreatment general aspects: After closing and capping of the rotor,

vessels were pressurized with 20 bar of oxygen


Analytes: Al, Fe, Mn, Sr and Zn

Characteristics of a novel UV-TiO2-microwave integrated irradiation

device in decomposition processes

Matusiewicz, H. and Stanisz, E., Microchemical Journal, 86 (1) 9–16, 2007

Abstract

The efficiency of oxidation in wet decomposition procedures for organic

materials can be of great importance to the quality of the analytical data

from various measurement techniques. A novel, microwave-assisted, high-

temperature/high-pressure UV-TiO2 digestion procedure was developed for

the accelerated decomposition of various biological samples. The technique

is based on a closed, pressurized, microwave digestion apparatus (MW).

UV irradiation is generated by immersed electrodeless Cd discharge lamp

operated by the focused microwave field in the single polymer vessel. To

enhance oxidation efficiency, a photocatalyst TiO2 was added to the

microwave heated Teflon bomb. Measures of digestion completeness were

provided by the appearance of carbon content and determination of trace

and minor elements, enabling a comparison of different digestion

procedures and sample types. Compared with other digestion systems,

unusually low residual carbon contents were obtained. For the organic

compounds and biological samples digested, the residual carbon content

was 1–2%, corresponding to a decomposition efficiency of 98–99%. The

potential of the MW-UV-TiO2 system was illustrated by the decomposition

of four certified reference materials (serum, urine, milk, arsenobetaine

solution) and subsequent determination of trace and minor elements.

Recoveries between 92% and 107% were found.

Type of sample: serum (no. 010017), urine (no. 108) IAEA-153 (Milk

powder) and CRM BCR-626 (Arsenobetaine solution), untreated sewage,

fruit juice, milk powder, urine and serum

Sample amount: 1 mL (serum), 4 mL (urine), 100 mg (milk powder), 50

μL (Arsenobetaine solution)

Microwave oven (model): UniClever pressurized microwave digestion

system from Plazmatronika (Wroclaw, Poland).

Vessel material: TFM-PTFE

Heating: Step 1: 5 min at 300 W. Step 2: 10 min at 200 W (300 °C)


Reagents: 170 μL HNO3 0.53 mol/L + 250 μL H2O2 0.49 mol/L + 5 mg

TiO2 + 5 mL H2O (or 6 mL H2O to milk powder)



Analytes: Al, Ca, Cu, Fe, Mg, Na, Se, Zn

Determination of trace elements in coal and coal fly ash by joint-use of

ICP-AES and atomic absorption spectrometry

Iwashita, A., Nakajima, T., Takanashi, H., Ohki, A., Fujita, Y. and

Yamashita, T., Talanta, 71 (1) 251–257, 2007

Abstract

Microwave-acid digestion(MW-AD) followed by inductively coupled

plasma-atomic emission spectrometry (ICP-AES), graphite furnace atomic

absorption spectrometry (GFAAS), and hydride generation atomic

absorption spectrometry (HGAAS) were examined for the determination of

various elements in coal and coal fly ash (CFA). Eight certified reference

materials (four coal samples and four CFA samples) were tested. The 10

elements (As, Be, Cd, Co, Cr, Mn, Ni, Pb, Sb, and Se), which are described

in the Clean Air Act Amendments (CAAA), were especially considered.

For coal, the HF-free MW-AD followed by ICP-AES was successful in the

determination of various elements except for As, Be, Cd, Sb, and Se. These

elements (except for Sb) were well-determined by use of GFAAS (Be and

Cd) and HGAAS (As and Se). For CFA, the addition of HF in the digestion

acid mixture was needed for the determination of elements, except for As,

Sb, and Se, for which the HF-free MW-AD was applicable. The use of

GFAAS (Be and Cd) or HGAAS (Sb and Se) resulted in the successful

determination of the elements for which ICP-AES did not work well. The

protocol for the determination of the 10 elements in coal and CFA by MW-

AD followed by the joint-use of ICP-AES, GFAAS, and HGAAS was

established.

Type of sample: coal and coal fly ash

Sample amount: 0.25 g (coal); 0.1 g (coal fly ash)

Microwave oven model: Milestone Ethos 1600 (Sorisole, Italy)


Heating: Stage 1 (110 ºC): a) 2 min, 250 W. b) 1 min, 0 W. c) 5 min, 250

W. d) 5 min, 400 W. e) 5 min, 500 W. f) 20 min, 400 W.

Stage 2 (130 ºC): a) 5 min, 250 W. b) 5 min, 400 W. c) 5 min, 500 W. d)

5 min, 600 W. e) 15 min, 400 W.


Reagents: HNO3, 61% (v/v); H2O2, 30% (m/v); HF, 46% (v/v).

Coal

Stage 1: 5 mL HNO3 + 3 mL H2O2


CFA

Stage 1: 5 mL HNO3 + 1 mL HF + 2 mL H2O2



Detection technique: ICP AES, GFAAS and HGAAS

Analytes: Al, Ca, Fe, Mg, As, Be, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Se, Ti,

V and Zn.

Evaluation of four sample treatments for determination of platinum in

automotive catalytic converters by graphite furnace atomic absorption

spectrometry

Puig, A.I. and Alvarado, J.I., Spectrochimica Acta Part B, 61 (9), 1050-

1053, 2006

Abstract

Conventional and microwave assisted digestion, both using aqua regia,

alkaline fusion with lithium metaborate and aqueous slurries were

evaluated as sample treatments for determination of Pt in automotive

catalytic converters by Graphite Furnace Atomic Absorption Spectrometry

(GF-AAS). Determination of platinum by GF-AAS in samples of the

catalytic converter's substrates, prepared by the four methods described,

indicates that the highest platinum concentration i.e. maximum Pt

extraction in the range of 748±15-998±10 μg mL−1, is obtained for samples

dissolved by alkaline fusion, closely followed by analysis of aqueous plus

Triton X-100 slurries 708±14-958±10 μg mL−1, while neither one of the

acid digestion procedures achieved total dissolution of the samples. Slurry

analysis is thus shown to be a viable alternative and is recommended, based

on its speed and ease of implementation. Aqueous standards calibration

curves and the standard addition methods were also compared. The results

showed that no appreciable matrix effects are present, regardless of the

sample preparation procedure used. Precision of the measurements,

expressed as percentage relative standard deviation, ranged between 2.5 to

4.9%. Accuracy of the results was assessed by recovery tests which

rendered values between 98.9 and 100.9%.

Kind of sample: automotive catalytic converters


Microwave oven (model): MDS 2000 (CEM)

Vial material: PTFE vessels

Program (Pressure and temperature): four heating steps at increasing

pressure 3.40, 6.80, 10.20 and 12.24 atm; a ramp time of 15 min between

steps; 15 min at each step after reaching pressure and 100% magnetron

power.

Number of simultaneous treated samples: 12

Reagents: 5 mL aqua regia


Detection technique: GF-AAS

Analytes: Pt

High-Throughput microwave-Assisted digestion and extraction

procedures for agricultural materials

Nobrega, J. A., Nascentes, C. C., Labuto, G. A. C., Nogueira, A. R. A. and

Pirola, C., Communications in Soil Science and Plant Analysis, 38 (17-18),

2333-2345, 2007

Abstract

Despite the advances in microwave-assisted procedures, the sample

throughput still remains a critical problem that requires the development of

reactor vessels, rotors, and procedures able to deal with a large number of

samples simultaneously. In this work, a 36-vessel rotor was combined with

dilute nitric acid solution for digestion of agricultural materials. Accurate

results were obtained for aluminum (Al), calcium (Ca), copper (Cu), iron

(Fe), potassium (K), magnesium (Mg), manganese (Mn), phosphorus (P),

and zinc (Zn) in bovine liver and spinach leaf standard reference materials.

The EPA-3051 method was also evaluated using this system. The

procedure led to quantitative recoveries of chromium (Cr), Cu, Mn, nickel

(Ni), and Zn in soil. All measurements were carried out using inductively

coupled plasma—optical emission spectrometry (ICP-OES). The main

advantages of the proposed procedures are the increase of sample

throughput in microwave-assisted digestions or extractions and the lower

dilution required before pneumatic nebulization of digests obtained by

using dilute nitric acid.

Type of sample: plant tissue (spinach leaf), animal tissue (bovine liver)

and soil

Sample amount: plant and animal tissue: 0.1 g and soil: 0.25 g

Microwave oven (model): Ethos-1600, Milestone, Sorisole, Italy with 36

glass reaction vessels (MultiPREP 36 rotor)


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Heating: plant and animal tissue: Step1: 2 min at 250W and 60°C. Step 2:

1 min at 0W and 60°C. Step 3: 4 min at 450W and 150°C. Step 4: 6 min at

550W and 180°C. Step 5: 6 min at 650W and 180°C. soil: the target

temperature (175°C) was reached in 7 min. After, this temperature was kept

for an additional 4.5 min


Reagents: plant and animal tissue: 2 mL of diluted HNO3 solutions (2.0,

3.0, 4.0, 5.0, 6.0, and 7.0 mol/L) + 1 mL H2O2 30% m/v; soil: 10 mL of

concentrated HNO3 65% m/v



Analytes: Al, Ca, Cu, Fe, K, Mg, Mn, P and Zn

ICP-OES Determination of metals present in textile materials

Rezić, I. and Steffan, I., Microchemical Journal, 85 (1), 46–51, 2007

Abstract

The aim of this work was to quantify the content of elements present in

textile materials since it is known that textiles containing metals may

represent a health hazard to consumers. Determination of metal content can

be also useful to the textile industry since some metals present in textiles

may contribute to problems during textile production. Extraction of metals

from different textile materials was performed in an artificial acidic sweat

solution according to the Öko Tex standard for materials coming into direct

contact with the skin. After extraction from textile products made of cotton,

flax, wool, silk, viscose, and polyester materials, all elements were

determined by means of inductively coupled plasmaoptical emission

spectrometry (ICP-OES). Results in the sweat extracts (minimum–

maximum in μg/mL) were: Al 0.11–1.58, Cd 0.02–0.05, Cr 0.01–0.32, Cu

0.05–1.95, Mn 0.01–2.17, and Ni 0.05–0.10. Concentrations of other

elements were bellow detection limits. The total amount of metals present

was determined after microwave assisted acidic digestion of textile

materials with 7 M nitric acid. According to the results, the majority of the

detected elements were below the concentration limits given by the Öko

Tex, and for this reason the textile materials investigated do not represent a

health hazard to consumers.

Type of sample: textile materials



Sorisole, Italy)


Heating: 5 min at 250 W (150 °C), 15 min at 300 W (180 °C) and 20 min

at 350 W (200 °C).


Reagents: 8 mL HNO3 7 mol/L

Pretreatment general aspects: Samples were dried for 48 h at 60 °C and

cut.


Analytes: Al, As, Be, B, Co, Cr, Cu, Fe, K, Mg, Mo, Ni, Si and Zn

Mercury and its bioconcentration factors in brown birch scaber stalk

(leccinum scabrum) from various sites in Poland

Falandysz, J. and Bielawski, L., Food Chemistry, 105 (2), 635-640, 2007

Abstract

The total mercury contents were determined in the carpophores of Brown

Birch Scaber Stalk (Leccinum scabrum) and topsoil (0–10 cm) collected

from 12 spatially distant sites across Poland. Mercury was measured by

cold-vapour atomic absorption spectroscopy (CV-AAS) after nitric acid

(mushrooms) or aqua regia (soil) digestion of the samples. The caps,

depending on the site, had total mercury concentrations from 0.38 ± 0.23 to

1.2 ± 0.4 l μg/g dm (median 0.36–1.2 μg/g dm), and stalks from 0.17 ±

0.08 to 0.72 ± 0.20 μg/g dm (median 0.17–0.72 μg/g dm). Overall-mean

mercury contents for 240 caps and stalks were 0.63 ± 0.38 (0.072–2.0 μg/g

dm) and 0.32 ± 0.20 (0.028–1.2 μg/g dm), respectively. The total mercury

content in top soil layer (0–10 cm) at 12 sites, after hot aqua regia

extraction, averaged 0.026 ± 0.010–0.066 ± 0.018 μg/g dm. The BCF

values of total mercury in caps of Brown Birch Scaber Stalk from the

particular sites ranged from 14 ± 5 to 20 ± 4 (total mean was 16 ± 5, and

median 18), in stalks from 6.0 ± 4.0 to 11 ± 1 (total mean was 8.3 ± 3.1,

and median 8.1). In human feeding, wild mushrooms are usually only a

small part of the total diet, so consumption of Brown Birch Scaber Stalk

collected from the background sites in Poland, or elsewhere in Europe, as

regards mercury content, could be considered safe.

Type of sample: carpophores and Topsoil


Microwave oven (model): MARS 5 of CEM Corporation, Matthews, NC,

USA



Number of simultaneous treated samples: 12

Reagents: 6 mL HNO3


Detection technique: CV-AAS

Analytes: Hg

Microwave-assisted extraction of rare earth elements from petroleum

refining catalysts and ambient fine aerosols prior to inductively

coupled plasma-mass spectrometry

Kulkarni, P., Chellam, S. and Mittlefehldt, D. W., Analytica Chimica Acta,

581 (2), 247-259, 2007

Abstract

A robust microwave-assisted acid digestion procedure followed by

inductively coupled plasma-mass spectrometry (ICP-MS) was developed to

quantify rare earth elements (REEs) in fluidized-bed catalytic cracking

(FCC) catalysts and atmospheric fine particulate matter (PM2.5). High

temperature (200 oC), high pressure (200 psig), acid digestion (HNO3, HF

and H3BO3) with 20 min dwell time effectively solubilized REEs from six

fresh catalysts, a spent catalyst and PM 2.5. This method was also employed

to measure 27 non-REEs including Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn,

Fe, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb and U.

Complete extraction of several REEs (Y, La, Ce, Pr, Nd, Tb, Dy and Er)

required HF indicating that they were closely associated with the

aluminosilicate structure of the zeolite FCC catalysts. Internal

standardization using 115In quantitatively corrected non-spectral

interferences in the catalyst digestate matrix. Inter-laboratory comparison

using ICP-optical emission spectroscopy (ICP-OES) and instrumental

neutron activation analysis (INAA) demonstrated the applicability of the

newly developed analytical method for accurate analysis of REEs in FCC

catalysts. The method developed for FCC catalysts was also successfully

implemented to measure trace to ultra-trace concentrations of La, Ce, Pr,

Nd, Sm, Gd, Eu and Dy in ambient PM2.5 in an industrial area of Houston,

TX.

Type of sample: PM2.5 samples, zeolite based fresh FCC catalysts and

spent zeolite FCC catalyst

Sample amount: 0.050 g of each catalyst and 0.002–0.005 g of PM2.5

samples.

Microwave oven (model): MARS 5, CEM Corporation, Matthews, NC,

USA

Vessel material: Teflon-lined

Heating: The effect of HF volume on digestion was evaluated for all the

catalysts using 5 mL of HNO3 65% (v/v) and volume of HF in each vessel

(0.00, 0.05, 0.10, 0.30, 0.50 or 1.00 mL). In the first stage, the temperature

was ramped to 200 oC with the application of 600 W power and time of 20

min. Only for the case of 0.3 mL HF 48% (v/v), lower temperature settings

of 150 and 175 oC were also evaluated. In the second stage, remaining HF

was complexed by adding stoichiometric excess of H3BO3 (5% (m/v)

solution corresponding to eight times the HF volume). The vessels were

recapped and heated again to set points of 200oC, 200 psig, with 20 min

dwell time. Ambient PM2.5 filters were also digested using the same two-

stage technique determined to be optimal for FCC catalysts (200 oC, 200

psig and 20 min dwell time).


Reagents: 0.00, 0.05, 0.10, 0.30, 0.50 or 1.00 mL HF 48% (v/v) + 5 mL

HNO3 65% (v/v) + excess of H3BO3 5% (m/v)

Pretreatment general aspects: All samples were dried at 80 oC for 4 h in a

clean oven and stored in a desiccator

Detection technique: ICP-MS, ICP OES and INAA

Analytes: Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga,

As, Se, Rb, Sr, Zr, Mo, Cd, Cs, Ba, Pb, U, Y, La, Tb, Er, La, Ce, Pr, Nd,

Sm, Gd, Eu and Dy

Multi-walled carbon nanotubes as sorbent for flow injection on-line

microcolumn preconcentration coupled with flame atomic absorption

spectrometry for determination of cadmium and copper

Liang, H. D. and Han, D. M., Analytical Letters, 39 (11), 2285-2295,

2006

Abstract

Multi-walled carbon nanotubes (MWNTs) were used as sorbent for flow

injection (FI) on-line microcolumn preconcentration coupled with flame

atomic absorption spectrometry (FAAS) for determination of trace

cadmium and copper in environmental and biological samples. Effective

preconcentration of trace cadmium and copper was achieved in a pH range

of 4.5–6.5 and 5.0–7.5, respectively. The retained cadmium and copper

were efficiently eluted with 0.5 mol/L HCl for on-line FAAS

determination. The MWNTs packed microcolumn exhibited fairly fast

kinetics for the adsorption of cadmium and copper, permitting the use of

high sample flow rates up to at least 7.8 mL/min for the FI on-line

microcolumn preconcentration system without loss of the retention

efficiency. With a preconcentration time of 60 sec at a sample loading flow

rate of 4.3 mL min-1, the enhancement factor was 24 for cadmium and 25

for copper at a sample throughput of 45 h-1. The detection limits (3s) were

0.30 and 0.11 mg/L for Cd and Cu, respectively. The precision (RSD) for

11 replicate measurements was 2.1 % at the 10 mg/L Cd level and 2.4% at

the 10 mg/L Cu level. The developed method was successfully applied to

the determination of trace Cd and Cu in a variety of environmental and

biological samples.

Type of sample: tea, human hair and rice flour

Sample amount: 2 g of tea was (for Cd), 0.25 g of tea (for Cu); 1 g of

human hair (for Cd), 0.3 g of human hair (for Cu); 1 g of rice flour.

Microwave oven (model): Qwave-2000 (Questron Corp.)



Heating: All instrumental parameters for the sample digestion were chosen

according to the recommendations of Environmental Protection Agency of

America (EPA).


Reagents: 20 mL HNO3 conc. (tea, for Cd); 5 mL HNO3 conc. (tea, for

Cu); 12 mL HNO3 conc. (human hair, for Cd); 6 mL HNO3 conc. (human

hair, for Cu); 10 mL HNO3 conc. (rice flour)



Analytes: Cu and Cd

Speciation of selenium(IV) and selenium(VI) in environmental samples

by the combination of graphite furnace atomic absorption

spectrometric determination and solid phase extraction on Diaion

HP-2MG

Saygi, K.O., Melek, E., Tuzen, M. and Soylak, M. Talanta, 71 (3), 1375-

1381, 2007

Abstract

A simple solid phase extraction procedure for speciation of selenium (IV)

and selenium (VI) in environmental samples has been proposed prior to

graphite furnace atomic absorption spectrometry. The method is based on

the solid phase extraction of the selenium (IV)–ammonium pyrrolidine

dithiocarbamate (APDC) chelate on the Diaion HP-2MG. After reduction

of Se (VI) by heating the samples in the microwave oven with 4 mol/L

HCl, the system was applied to the total selenium. Se (VI) was calculated

as the difference between the total selenium content and Se (IV) content.

The experimental parameters, pH, amounts of reagents, eluent type and

sample volume were optimized. The recoveries of analytes were found

greater than 95%. No appreciable matrix effects were observed. The

adsorption capacity of sorbent was 5.20 mg/g Se (IV). The detection limit

of Se (IV) (3sigma, n = 11) is 0.010 μg/L. The preconcentration factor for

the presented system was 100. The proposed method was applied to the

speciation of selenium (IV), selenium (VI) and determination of total

selenium in natural waters and microwave digested soil, garlic, onion, rice,

wheat and hazelnut samples harvested various locations in Turkey with

satisfactory results. In order to verify the accuracy of the method, certified

reference materials (NIST SRM 2711 Montana Soil, NIST SRM 1568a

Rice Flour and NIST SRM 8418 Wheat Gluten) were analyzed and the

results obtained were in good agreement with the certified values. The

relative errors and relative standard deviations were below 6 and 10%,

respectively.

Type of sample: soil, garlic, onion, rice, wheat and hazelnut




Heating: Step 1: 250 W, 3 min. Step 2: 450 W, 5 min. Step 3: 650 W, 5

min. Step 4: ventilation 8 min.


Reagents: 6 mL HNO3 conc. + 2 mL H2O2 conc. (garlic, onion, rice, wheat

and hazelnut) or 6 mL HCl conc. + 2 mL HNO3 conc. (soil)



Analytes: Se

Combination of ultrasonic extraction and stripping analysis: An

effective and reliable way for the determination of Cu and Pb in

lubricating oils

Munoz, R. A. A., Oliveira, P. V. and Angnes, L., Talanta, 68 (3), 850-856,

2006

Abstract

The determination of metals in lubricating oil has been used as an

important way to prevent components failures, to provide environmental

information and in some cases, to identify adulteration. In this work, an

effective and simple procedure is proposed for Cu and Pb determination in

lubricating oils. An ultrasonic bath was employed for extraction of these

elements from oil samples in a mixture 1:1 (v/v) of concentrated HCl and

H2O2. A very efficient extraction of Cu and Pb (100%) was attained after

30 min of ultrasound, allowing the simultaneous determination of both

metals using square-wave anodic stripping voltammetry at thin-film gold

electrodes. The extraction procedure was performed in 4 mL polypropylene

closed vessels and dozens of samples could be treated simultaneously in the

same ultrasonic bath. The regions of the ultrasonic bath, where the

maximum efficiency of extraction was attained were evaluated. Over the

optimized region, 30 samples can be treated simultaneously. Used

lubricating oils from automotive engines were analyzed by using the

optimized extraction procedure.

Type of sample: used lubricating oils


Microwave oven (model): Star System 2 (CEM Corporation, Matthews,

NC, USA)


Heating: sequence ramp of temperature ranging from 100–220 °C were

applied, total time: 38 min. After that, 15 mL of hydrogen peroxide 30% is

added together and the temperature is maintained at 220 °C for 7 min.


Reagents: 10 mL of (both) HNO3 and H2SO4 conc. and 15 mL of H2O2

30% (m/v)


Detection technique: Square-wave stripping voltammetry and GF AAS

Analytes: Cu and Pb

Determination of Mo, Zn, Cd, Ti, Ni, V, Fe, Mn, Cr and Co in crude oil

using inductively coupled plasma optical emission spectrometry and

sample introduction as detergentless microemulsions

Souza, R. M., Meliande, A. L. S., Silveira, C. L. P. and Aucélio, Q. C.,

Microchemical Journal, 82 (2), 137-141, 2006

Abstract

A procedure to prepare crude oil samples as detergentless microemulsions

was optimized and applied for the determination of Mo, Zn, Cd, Si, Ti, Ni,

V, Fe, Mn, Cr and Co by ICP OES. Propan-1-ol was used as a co-solvent

allowing the formation of a homogeneous and stable system containing

crude oil and water. The optimum composition of the microemulsion was

crude oil/propanol/water/ concentrated nitric acid, 6/70/20/4 w/w/w/w. This

simple sample preparation procedure together with an efficient sample

introduction (using a Meinhard K3 nebulizer and a twister cyclonic spray

chamber) allowed a fast quantification of the analytes using calibration

curves prepared with analyte inorganic standards. In this case, Sc was used

as internal standard for correction of signal fluctuations and matrix effects.

Oxygen was used in the nebulizer gas flow in order to minimize carbon

building up and background. Limits of detection in the ng/g range were

achieved for all elements. The methodology was tested through the analysis

of one standard reference material (SRM NIST 1634c, Residual Fuel Oil)

with recoveries between 97.9% and 103.8%. The method was also applied

to two crude oil samples and the results were in good agreement with those

obtained using the acid decomposition procedure. The precision (n = 3)

obtained was below 5% and the results indicated that the method is well

suited for oil samples containing low concentrations of trace elements.

Type of sample: Crude oil



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USA)


Heating: The cups were sealed and subjected once to a three-step digestion

program: 5 min at 300 W, 1 min at 0 W and 5 min at 600 W. A second

addition of concentrated nitric acid (2 mL) was made to each vessel and,

then, the sealed cups were subjected to three cycles of the digestion

program. After the solution has cooled down (30 min), 1 mL of H2O2 was

added to the vessel. The solution was submitted once to the program

mentioned above.


Reagents: 2 mL HNO3 conc. + 1 mL H2O2 30% (m/v)

Pretreatment general aspects: Detergentless microemulsions were

prepared using propanol as the co-solvent and water.


Analytes: Mo, Zn, Cd, Ti, Ni, V, Fe, Mn, Cr and Co

Determination of trace elements in crude oil by ICP-OES using

ultrasound-assisted acid extraction

Souza, R. M., Saraceno, A. L., Silveira, C. L. P. and Aucélio, R. Q.,

Journal of Analytical Atomic Spectrometry, 21 (11), 1345-1349, 2006

Abstract

The determination of Cr, Mo, Ti, V, Cd, Fe, Mn, Ni and Zn in crude oil by

ICP-OES using ultrasound-assisted acid extraction is proposed. The crude

oil was treated with concentrated nitric acid and heated at 85 °C for 30 min.

Then, the mixture was placed in an ultrasonic bath for 15 min in order to

obtain total extraction of trace elements from the oil sample into the acid

solution, which was directly aspirated into the ICP to be quantified using

analytical curves constructed with inorganic standards. Principal

component analysis (PCA) and factor analysis (FA) were used to evaluate

the effect and importance of the experimental variables in this sample

preparation procedure. The proposed method was tested using NIST 1634c

(Trace Elements in Residual Fuel Oil) and two petroleum samples.

Recoveries between 90 and 105% were achieved. Limits of quantification

in the sample ranged from 0.008 to 0.62 µg/g, depending on the analyte.

Type of sample: Crude oil


Microwave oven (model): MARS 5 (CEM Corporation, Matthews, NC

USA)


Heating: 5 min at 300 W, 1 min at 0 W and 5 min at 600 W. Before each

of the subsequent runs, the Teflon bomb was allowed to cool down

(25 min) and a new aliquot of 2 mL of concentrated HNO3 (second and

third runs) or 1 mL of H2O2 (fourth run) was added to the vessel.

Number of samples simultaneously digested: four

Reagents: 2.0 mL HNO3 conc. + 1 mL H2O2 30% (m/v)



Analytes: Cr, Mo, Ti, V, Cd, Fe, Mn, Ni and Zn

Focused-microwave-assisted digestion of encapsulated lubricanting

oils: gradual sample addition to pré-heated acid

Bressani, F. A., Silva, H. O., Nóbrega, J. A., Costa, L. M. and Nogueira, A.

R. A., Química Nova, 29 (6), 1210-1214, 2006

Abstract

Focused microwave-assisted digestion of encapsulated lubricating oils:

gradual sample addition to pre-heated acid. The applicability of the recently

proposed procedure based on gradual sample addition to microwave-

assisted pre-heated concentrated acid is limited by the sample viscosity. In

this work, lubricating oil samples with high viscosity were encapsulated

and manually added to the microwave-assisted pre-heated concentrated

digestion mixture. The procedure was applied for determination of Al, Ca,

Cr, Cu, Fe, Mg, Ni, P, Pb, Si, Sn, Sr, V, W, and Zn in lubricating oil by

inductively coupled plasma optical emission spectrometry (ICP OES).

Determined and certified values for Ca, Mg, P, and Zn in lubricating oil

were in agreement at a 95% confidence level.

Type of sample: lubricating oil


Microwave oven (model): STAR 6 (CEM Corporation, Matthews, NC,

USA)


Heating: Conventional procedure: 10 mL of concentrated H2SO4 and 5 mL

of concentrated HNO3: until reached the temperature of 95 ºC. After, more

2 mL of concentrated HNO3 were added and the temperature was set to

250 ºC. Then, 2 mL and 1 mL of concentrated HNO3 were added. In order

to complete the digestion cycle, after the sample cooling until 200 ºC (10

min), 20 mL of H2O2 were added.

Developed procedure: 3 mL of concentrated H2SO4 and 4 mL of

concentrated HNO3. The mixture was heated at 130 ºC for 2 min. After,

more 2 aliquots of 1.5 mL of concentrated HNO3 were added and the

temperature was selected to 150 ºC for 6 min. Then, 10 mL of H2O2, in

aliquots of 1 mL, were added and the temperature was reached to 180 ºC

for 10 min.

Number of samples simultaneously digested: one

Reagents: H2SO4 conc., HNO3 conc. and H2O2 30% (m/v)

Pretreatment general aspects: for the sample digestion using the

developed to the pre-heated acid procedure, the samples were encapsulated

and gradually added


Analytes: Al, Ca, Cr, Cu, Fe, Mg, Ni, P, Pb, Si, Sn, Sr, V, W, and Zn.

Optimization of an open-focused microwave oven digestion procedure

for determination of metals in diesel oil by inductively coupled plasma


Sant'Ana, F. W., Santelli, R. E., Cassella, A. R. and Cassella, R. J., Journal

of Hazardous Materials, 149 (1), 67-74, 2007

Abstract

This work reports the optimization of a focused microwave assisted

procedure for the wet acid dissolution of diesel oil in order to allow the

determination of metals in the samples by inductively coupled plasma

optical emission spectrometry (ICP-OES). The dissolution process was

monitored by measuring residual carbon content (RCC), also by ICP-OES,

in the final solutions obtained after application of digestion program. All

experimental work was performed using a commercial sample of diesel oil

containing 85.74 ± 0.13% of carbon. The initial dissolution program

comprised three steps: (i) carbonization with H2SO4; (ii) oxidation with

HNO3 and (iii) final oxidation with H2O2. During work it was verified that

the first step played an important role on the dissolution process of this

kind of sample. It is therefore, necessary to give a detailed optimization of

such step. Employing the optimized conditions it was possible to digest

2.5 g of diesel oil with a 40 min-heating program. At these conditions,

residual carbon content was always lower than 5%. Optimized

methodology was applied in the determination of metals in three diesel oil

samples by ICP-OES. Recovery tests were also performed by adding 10 µg

of metals, as organic standards, to the samples before digestion. Recovery

percentages always higher than 90% were obtained for the metals of

interest (Al, Cu, Fe and Ni), except for Zn, which presented recoveries

between 70 and 78 %.

Type of sample: diesel oil






Microwave oven (model): Microdigest 3.6, CEM Corp., Matthews, NC,

USA

Vessel material: Borosilicate

Heating: 5 mL of concentrated H2SO4: 5 min at 60 W. After, more 5 mL of

concentrated H2SO4 were added: 10 min at 120 W and 10 min at 150 W.

Then, 4 mL of concentrated HNO3: 10 min at 210 W. In order to complete

the digestion cycle, 10 mL of H2O2 were added and the mixture was

irradiated for more 5 min.


Reagents: 10 mL H2SO4 + 4 mL HNO3 + 10 mL H2O2



Analytes: Al, Cu, Fe, Ni and Zn

Trace elemental characterization of edible oils by ICP–AES and

GFAAS

Cindric, I. J., Zeiner, M. and Steffan, I., Microchemical Journal, 85 (1),

136–139, 2007

Abstract

A method for the determination of the inorganic profile in edible oils is

proposed. The quantification of selected metals in various oils (olive,

pumpkin seed, sunflower, sesame seed, hazelnut, grape, soya, rice oil) was

carried out using microwave assisted digestion followed by ICP–AES and

GFAAS detection. The detection power of the ICP–AES technique was

sufficient for the determination of Ca, Fe, Mg, Na, and Zn. Since the

samples contained very low amounts of Al, Cu, Co, Cr, K, Ni, Mn, and Pb,

these elements were measured by GFAAS. Differences of metal

concentrations for edible oils obtained in this preliminary study represent a

starting basis for the development of an additional analytical procedure

applicable for oil characterization.

Type of sample: edible oils


Microwave oven (model): MLS-1200 MEGA with an EM-30


Heating: Step 1: 2 min at 250W. Step 2: 1 min at 0 W. Step 3: 2 min at 250

W. Step 4: 1 min at 600 W. Step 5: 5 min at 400 W. Step 6: ventilation

3 min


Reagents: 4 mL HNO3 65% + 2 mL H2O2 30%


Detection technique: ICP AES and GFAAS

Analytes: Al, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn

An ultrasound-assisted digestion method for the determination of toxic

element concentrations in ash samples by inductively coupled plasma


Ilander, A. and Vaisanen., Analytica Chimica Acta, 602 (2), 195-201, 2007

Abstract

A method of ultrasound-assisted digestion followed by inductively coupled

plasma optical emission spectrometry (ICP-OES) used for the

determination of toxic element concentrations (arsenic, barium, cobalt,

copper, lead, nickel, strontium, vanadium and zinc) in ash samples was

developed. All the measurements were performed in robust plasma

conditions which were tested by measuring the Mg(II) 280.270 nm/Mg(I)

285.213 nm line intensity ratios. The highest line intensity ratios were

observed when a nebulizer gas flow of 0.6 L/min, auxiliary gas flow of

0.2 L/min and plasma power of 1400 W were used for radially viewed

plasma. The analysis of SRM 1633b showed that the ultrasound-assisted

method developed is highly comparable with the microwave digestion

method standardized by the United States Environmental Protection

Agency (EPA-3052). The ultrasound-assisted digestion with a digestion

solution of aqua regia and hydrofluoric acid (HF) resulted in recovery rates

of over 81%. One exception is arsenic which resulted in recoveries of about

60% only; however, it could be digested with good recovery

(> 90%) using a digestion solution of 5 mL of water and 5 mL of aqua

regia. The major advantage of the ultrasound-assisted digestion over

microwave digestion is the high treatment rate (30 samples simultaneously

with a sonication time of 18 min).

Type of sample: ash


Microwave oven (model): ETHOS PLUS microwave digestion system,

Milestone (Sorisole, Italy)


Heating: Step 1: 5 min, 1000 W and 180 oC. Step 2: 10 min, 1000 W and

180 oC


Reagents: 9 mL of HNO3 and 3 mL of HF



Analytes: As, Ba, Co, Cu, Pb, Ni, Sr, V, and Zn

Characterization and determination of 28 elements in fly ashes

collected in a thermal power plant in Argentina using different

instrumental techniques

Marrero, J., Polla, G., Rebagliati, R. J., Plá, R., Gómez, D. and

Smichowski, P., Spectrochimica Part Acta B, 62 (2), 101-108, 2007

Abstract

Different techniques were selected for comprehensive characterization of

seven samples of fly ashes collected from the electrostatic precipitator of

the San Nicolás thermal power plant (Buenos Aires, Argentina). Particle

size was measured using laser based particle size analyzer. X-ray

diffraction powder (XRD) analysis and scanning electron microscopy

(SEM) were used to characterize the mineral phase present in the matrix

consisting basically of aluminosilicates and large amounts of amorphous

material. The predominant crystalline phases were mullite and quartz.

Major and minors elements (Al, Ca, Cl, Fe, K, Mg, Na, S, Si and Ti) were

detected by energy dispersive X-ray analysis (EDAX). Trace elements (As,

Cd, Co, Cr, Cu, Mn, Ni, Pb, Se, Vand Zn) content was quantified by

inductively coupled plasma optical emission spectrometry (ICP OES).

Different acid mixtures and digestion procedures were compared for

subsequent ICP OES measurements of the dissolved samples. The

digestion procedures used were: i) a mixture of HF+HNO3+HClO4 (open

system digestion); ii) a mixture of HF+HNO3 (MW-assisted digestion); iii)

a mixture of HF and aqua regia (MW-assisted digestion). Instrumental

neutron activation analysis (INAA) was employed for the determination of

As, Ba, Co, Cr, Ce, Cs, Eu, Fe, Gd, Hf, La, Lu, Rb, Sb, Sc, Sm, Ta, Tb, Th,

U and Yb. The validation of the procedure was performed by the analysis

of two certified materials namely, i) NIST 1633b, coal fly ash and ii)

GBW07105, rock. Mean elements content spanned from 41870 μg/g for Fe

to 1.14 μg/g for Lu. The study showed that Fe (41870 μg/g)�V (1137

μg/g)> Ni (269 μg/g)> Mn (169 μg/g) are the main components. An

enrichment, with respect to crustal average, in many elements was

observed especially for As, V, and Sb that deserve particular interest from

the environmental and human health point of view.

Type of sample: fly ash


Microwave oven (model): MLS-2000


Heating: 2 min at 250 W; 2 min at 0 W; 6 min at 250 W; 5 min at 400 W;

6 min at 650 W


Reagents: 3 mL HF concentrated + 8 mL of aqua regia

Pretreatment general aspects: A mixture of 3 mL of HF and 8 mL of

aqua regia was added to the SRM, placed in PTFE vessels which were then

allowed to undergo overnight digestion. Samples were finally subjected to

microwave (MW)-assisted acid digestion in an MW oven.

Detection technique: XRD, SEM, EDAX, ICP OES, INAA

Analytes: As, Ba, Ce, Cd, Co, Cr, Cs, Cu, Eu, Fe, Gd, Hf, La, Lu, Mn, Ni,

Pb, Rb, Sb, Sc, Se, Sm, Ta, Tb, Th, U, V, Yb, Zn

Comparison of different sampling heads applied for investigation of

welding fume

Berlinger, B., Náray, M. and Záray, G., Microchemical Journal, 85 (1), 25–

30, 2007

Abstract

Welding fume samples were collected in two Hungarian welding plants,

where different types of steels were welded with metal active gas (MAG)

welding. Welding fumes were sampled with “fixed point” and personal

sampling techniques applying different sampling heads: Institute of

Occupational Medicine (IOM) sampler and conical inhalable sampler (CIS)

for the inhalable aerosol fraction and the Higgins-Dewell (HD) cyclone for

the respirable fraction. When sampled, the welding fume samples were

digested with the mixture of nitric acid and hydrogen peroxide in a closed

vessel microwave digestion system. The Cr, Mn, Ni and Co contents of the

solutions were determined by inductively coupled plasma atomic emission

spectrometry (ICP-AES) and inductively coupled plasma mass

spectrometry (ICP-MS). Iron was analysed only by the ICP-AES method.

Metal concentrations of the workplace air were calculated for the three

samplers, and the results were compared to each other. The differences of

the metal concentrations determined by the different inhalable sampling

heads, which were paired during the sampling, proved not to be significant.

Therefore, the IOM and CIS heads can be equally used for the sampling of

welding fume. Finally, the distributions of metals were determined between

the inhalable and respirable fractions. Metal concentrations in the

respirable aerosol fraction were 57–98% of the concentrations in the

inhalable fraction. These high rates of metals in the respirable aerosol call

the attention to the increased health risk of the welding fume.

Type of sample: welding fume (membrane filter)


Microwave oven (model): MARS 5, CEM, Matthews, NC, USA


Heating: 25 min at 600W, 10.88 atm, 210 °C


Reagents: 2 mL HNO3 70% + 0.5 mL H2O2 30%


Detection technique: ICP AES and ICP-MS

Analytes: Cr, Mn, Ni, Co, and Fe

Effect of pretreatment conditions on the determination of major and

trace elements in coal fly ash using ICP-AES

Iwashita, A., Nakajima, T., Takanashi, H., Ohki, A., Fujita, Y.and

Yamashita, T., Fuel, 85 (2), 257-263, 2006

Abstract

Microwave-assisted acid digestion (MW-AD) followed by atomic

spectrometries such as inductively coupled plasma-atomic emission

spectrometry (ICP-AES) was examined for the determination of major and

trace elements in coal fly ash (CFA). Effective digestion conditions were

studied using four certified reference materials of CFA, with particular

focus on the composition of acid mixture and the removal of HF after MW-

AD. When MW-AD was conducted without using HF (HNO3 + H2O2), the

tested elements yielded fairly poor recoveries. When MW-AD with HF

(HNO3 + HF + H2O2) was carried out, two methods for HF removal were

attempted, H3BO3 addition and evaporation of acids. In the former method,

while the recoveries of major elements (Al, Ca, Fe, and Mg) were

satisfactory, those of trace elements were not satisfactory; in particular, the

recovery of Pb was fairly low. In the latter method, the recoveries of Al,

Ca, and Mg were extremely poor; however, those of other elements

including the trace elements (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) were

satisfactory. In this paper, the optimization of the digestion method for

ICP-AES is discussed. Further, the advantages and limitations of ICP-AES

in the determination of elements in CFA are assessed.

Type of sample: coal fly ash


Microwave oven (model): ETHOS 1600 (Milestone Corporation, Sorisole,

Italy)


Heating: First stage: 250 W for 2 min at 110 ºC, 0 W for 1 min at 110 ºC,

250 W for 5 min at 110 ºC, 400 W for 5 min at 110 ºC, 500 W for 5 min at

110 ºC and 400 W for 20 min at 110 ºC.

Second stage: after the first stage and the addition of more acids, the

microwave processing was repeated using 250 W for 5 min at

130 ºC, 400 W for 5 min at 130 ºC, 500 W for 5 min at 130 ºC, 600 W for

5 min at 130 ºC and 400 W for 15 min at 130 ºC.


Reagents: for the first stage 5 mL of concentrated HNO3 and 3 mL of H2O2

30% (m/v) or 5 mL of concentrated HNO3, 1 mL of HF 48% and 2 mL of

H2O2 30% (m/v) were used. After the digestion, the vessels were remove

and more 2 mL of concentrated HNO3 and 1 mL of H2O2 30% (m/v) were

added (second stage).


Detection technique: ICP AES

Analytes: Al, Ca, Fe, Mg, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn

Microwave digestion – ICP-MS for elemental analysis in ambient

airbone fine particulate matter: Rare earth elements and validation

using a filter borne fine particle certified reference material

Kulkarni, P., Chellan, S., Flanagan, J. B. and Jayanty, R. K. M., Analytica

Chimica Acta, 599 (176), 170-176, 2007

Abstract

NIST standard reference material SRM 2783 was employed to validate a

high temperature, high pressure, two-stage microwave assisted acid

digestion procedure using HNO3, HF and H3BO3 developed for the analysis

of trace elements (including rare earths) in atmospheric fine particulate

matter (PM 2.5) prior to inductively coupled plasma mass spectrometry

(ICP-MS). This method quantitatively solubilized Na, Mg, Al, K, Ti, V,

Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sb, Cd, Cs, Ba, Pb, Th, U and several

rare earth elements (REEs) (La, Ce, Pr, Nd, Gd, Dy, Er, Sm and Eu) from

SRM 1648 and SRM 2783. A small amount of HF in the first stage was

required to dissolve silicates necessitating the corresponding addition of

H3BO3 in second stage to dissolve fluoride precipitates of Mg, La, Ce and

Th. The optimized microwave dissolution—ICP-MS method detected Na,

Mg, Al, K, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr, Cd, Mo, Sb, Cs,

Ba, La, Ce, Pr, Nd, Sm, Gd, Pb, Th and U at trace to ultra-trace levels in

ambient airborne fine particles from three sites in North Carolina. La to

light lanthanide signature ratios suggested that soil and motor vehicles are

the dominant REE sources in SRM 2783 and PM2.5 samples collected

during this study.

Type of sample: atmospheric fine particulate matter


Microwave oven (model): (MARS 5, CEM Corp., Matthews, NC, USA)


Heating: In the first stage, the temperature was ramped to 200 oC within 20

min followed by a dwell time of 20 min (with a pressure setting of 200

psig). The vessels were then cooled for 60–90 min, and then vented and

opened. For dual-stage digestions, 5% (m/v) H3BO3 was then added (to

mask free fluoride ions in the solution and redissolve fluoride precipitates),

the vessels were recapped, placed again in the microwave and heated for a

second time to the same microwave settings.


Reagents: Four digestion procedures were evaluated: (1) single stage with

3 mL HNO3 alone, (2) single stage with 3 mL HNO3 and 0.3 mL HF, (3)

dual stage with 3 mL HNO3 and 0.3 mL HF in the first stage and 2.4 mL

H3BO3 in the second stage and (4) dual stage with 3 mL HNO3 and 1mL

HF in the first stage with 8 mL H3BO3 in the second stage



Analytes: Na, Mg, Al, K, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Rb, Sr,

Cd, Mo, Sb, Cs, Ba, La, Ce, Pr, Nd, Sm, Gd, Pb, Th and U

Simultaneous measurements of arsenic, bromine, and iodine in coal

and coke by inductively coupled plasma-mass spectrometer

Chuan, G. Y., Fen, G. Q., Xing, S. M., Xiu, Z. Z. and Hong, C. Z., Chinese

Journal of Analytical Chemistry, 35 (8), 1175-1178, 2007

Abstract

Using high pressure and closed microwave digestion technology, the

imports and exports of coal and coke samples from different countries were

digested quickly with mixed acids of nitric acid, hydrofluoric acid, and

hydrogen peroxide solution, with the help of Inductively Coupled Plasma

Mass Spectrometer (ICP-MS), a method was established for simultaneous

determination of trace elements, such as, arsenic (As), bromine (Br) and

iodine (I) in coal and coke. The influence of the medium of nitric acid and

other acids on the determined elements was researched. The unstable mass

signal of bromine and iodine on account of different valencies could be

made stable by adding sodium persulfate. And the silver ion could catalyze

and accelerate the reaction mentioned earlier. High memory effect of

halogen was effectively decreased by a washing step with neutral mixed

lotion. The low detection limits were in the range of 0.1–5.0 μg/L with

relative standard deviations of 1.5%-12.0%, and the recoveries were in the

range of 80%-106.7%. The analysis results were satisfactory.

Type of sample: coil and coke


Microwave oven (model): ETHOS Touch Control microwave digestion

oven (Milestone Corp.), Sorisole, Italy.


Heating: digesting reaction system at 1000 W and rising temperature for

15–20 min, followed by 30–50 min at 200 oC


Reagents: 7–8 mL of HNO3, 1–2 mL HF, and 2 mL of H2O2



Analytes: As, Br and I

An improved procedure for phosphorus fractionation in plant material

explointing sample preparation and monosegment flow analysis

Maruchi, A. K., Rocha, F. R. P., Microchemical Journal, 82 (2), 207-213,

2006

Abstract

Sample treatment procedures were evaluated for fractionation of

phosphorous in plant materials (determination of organic and inorganic,

soluble and insoluble fractions). The procedures aimed the conversion of

different species into orthophosphate, minimizing time, reagent amounts

and waste generation. A monosegmented flow system with

multicommutation was developed for the spectrophotometric determination

of orthophosphate by the molybdenum blue method. Linear response

within 0.5 and 25.0 mg/L P, detection limit of 24 μg/L P (99.7%

confidence level), coefficient of variation of 3.5% (n=10) and sampling rate

of 38 measurements per hour were estimated. Each determination

consumes 5.0 mg ascorbic acid and 0.60 mg of ammonium molybdate.

Total phosphorous determination can be carried out after microwave-

assisted acid digestion by employing 100 mg of plant material and 500 μL

of concentrated HNO3. Extraction of soluble phosphorous can be carried

out with water by stirring for 10 min and organic soluble phosphorous can

be determined either after microwave-assisted acid digestion or

photodegradation in the presence of ammonium persulfate in acid medium.

The results for the different fractions agreed with those obtained by

ICP OES at the 95% confidence level

.Type of sample: plant materials






Heating: Program 1 1) ramp (5 min)/hold (1 min): 140 W; 2) ramp

(4 min)/hold (5 min): 180 W; 3) ramp (4 min)/hold (10 min): 220 W. In the

Program 2: 1) ramp (5 min)/hold (1 min): 140 °C: 2) ramp (4 min)/hold

(5 min): 180 °C; 3) ramp (4 min)/hold (10 min): 220 °C.


Reagents: 0.5 mL HNO3 65% (v/v) + 5.5 mL H2O2 30% (m/v)

Pretreatment general aspects: Samples were dried at 60 °C with air

circulation for 48 h and the material was ground in a cutting mill producing

solid particles with diameter lower than 1 mm.


Analytes: P

Application of LC/MS and ICP/MS for establishing the fingerprint

spectrum of the traditional Chinese medicinal preparation

Gan-Lu-Yin

Lin, I.H., Lee, M.C. and Chuang, W.C., Journal of Separation Science, 29

(1), 172-179, 2006

Abstract

We developed a method to analyze the fingerprint spectrum qualitatively

and quantitatively for the traditional Chinese herbal medicinal preparation

Gan-Lu-Yin with HPLC combined with photodiode array detection, and

MS, and to identify the preparation’s 14 main components including

baicalin, baicalein, oroxylin A-7-O-glucuronide, wogonin-7-O-

glucuronide, wogonin, and oroxylin A in Radix Scutellariae; naringin and

neohesperidin in Aurantii fructus; liquiritigenin, liquiritin, and glycyrrhizic

acid in Radix Glycyrrhizae. In LC/UV assay, a Cosmosil 5C18-MS-II

column was used as the stationary phase, and a gradient of potassium

dihydrogen phosphate, ACN, and water as the elute solution. The UV

detection wavelengths were 250 and 280 nm. In LC/MS assay, a gradient

of phosphoric acid, ACN, and water was used as the elute solution, and

electrospray positive ion mode ((+)-ESI) as the analytic mode. In order to

explore the distribution of trace metal elements effectively in Gan-Lu-Yin,

a microwave digestion method was used for sample treatment, and an

inductively coupled plasma MS assay was used to analyze fingerprint

spectra of the inorganic metals in Gan-Lu-Yin. Combined with fingerprint

spectra of organic compounds by LC/UV and LC/MS, it was expected to

provide effective quality control in the production of Gan-Lu-Yin.

Type of sample: herbal medicines


Microwave oven (model): MARS5 (CEM Corporation, Matthews, NC,

USA)




Vessel material: -

Heating: the mixture was incubated for 10 min. After, the digestion

program was as follow: stage 1: 10 min until 1200 W (40.82 atm, 150 ºC)

and 5 min at 150 ºC. Stage 2: 15 min until 1200 W (40.82 atm, 190 ºC) and

10 min at 190 ºC. After complete digestion and cooling to room

temperature, the solution was filtered through a 0.45 µm filter membrane

and water was added to the filtrate to make the total volume 100 mL.




Detection technique: ICP-MS, LC/MS

Analytes: Na, Mg, K, Ca, Fe, As, Cd, Hg and Pb (semiquantitative mode)

Biosorption of heavy metals on Aspergillus fumigatus immobilized

Diaion HP-2MG resin for their atomic absorption spectrometric

determinations

Soylak, M., Tuzen, M., Mendil, D. and Turkeku, I., Talanta, 70 (5), 1129-

1135, 2006

Abstract

A solid phase extraction procedure based on biosorption of copper(II),

lead(II), zinc(II), iron(III), nickel(II) and cobalt(II) ions on Aspergillus

fumigatus immobilized Diaion HP-2MG has been investigated. The

analytical conditions including amounts of A. fumigatus, eluent type, flow

rates of sample and eluent solutions were examined. Good recoveries were

obtained to the spiked natural waters. The influences of the concomitant

ions on the retentions of the analytes were also examined. The detection

limits (3 sigma, n = 11) were 0.30 μg/L for copper, 0.32 μg/L for iron,

0.41 μg/L for zinc, 0.52 μg/L for lead, 0.59 μg/L for nickel and 0.72 μg/L

for cobalt. The relative standard deviations of the procedure were below

7%. The validation of the presented procedure is performed by the analysis

of three standard reference materials (NRCC-SLRS 4 Riverine Water,

SRM 1515 Apple leaves and GBW 07605 Tea). The procedure was

successfully applied for the determination of analyte ions in natural waters,

microwave digested samples including street dust, tomato paste, black tea,

etc.

Type of sample: canned fish, tomato paste, street dust, black tea sample

and the reference materials Tea (GBW 07605) and apple leaves (SRM

1515).

Sample amount: 1.0 g and 0.25 g (reference materials)

Microwave oven (model): Ethos D (Milestone Corporation, Sorisole,

Italy)


Heating: 6 min at 250 W, 6 min at 400 W, 6 min at 550 W, 6 min for 250

W and vent: 8 min.


Reagents: HNO3 conc. and 2 mL of H2O2 30% (v/v)



Analytes: Cu, Pb, Zn, Fe, Ni and Co

Comparison between hydride generation and nebulization for sample

introduction in the determination of lead in plants and water samples

by inductively coupled plasma mass spectrometry, using external

calibration and isotope dilution

Petrov, P. K., Wibetoe, G. and Tsalev, D. L., Spectrochimica Acta Part B,

61 (1), 50–57, 2006

Abstract

Four inductively coupled plasma mass spectrometric methods: nebulization

sample introduction with external calibration; hydride generation with

external calibration; isotope dilution with nebulization; and isotope dilution

with hydride generation, have been tested and compared. Multimode

Sample Introduction System (MSISi) was employed in either nebulization

or hydride generation mode. Best limits of detection (below 0.1 Ag L-1) and

accuracy were obtained for isotope dilution techniques in hydride

generation and sample nebulization mode. A mixture of HNO3 and H2O2

served both for microwave-assisted digestion as well as a medium for

subsequent plumbane generation. Optimal reagent concentrations for

hydride generation stage were 0.1 mol/L HNO3, 0.28 mol/L H2O2 and 1.5%

m/v NaBH4. Critical effects of acidity, blanks and concomitants have been

discussed. Analytical methods were validated by use of plant and water

certified reference materials and spiked high salt solutions (seawater and

20% m/v NaCl) at lead levels in nanograms per gram to micrograms per

gram range.

Type of sample: plants and water


Microwave oven (model): Ethos 1600 (Milestone Corporation, Sorisole,

Italy)


Heating: The temperature was increased linearly from 25 to 200 °C

(250 °C for BCR CRM 60) for 10 min, kept for 20 min and then cooled to

room temperature. Then samples and blanks were transferred to 250 mL

volumetric glass flasks, 5.25 mL H2O2 was added and contents were diluted

to the mark with deionized water.


Reagents: 1.75 mL HNO3 conc. + 0.75 mL H2O2 30% (m/v) + 5.25 mL

H2O2 30% (m/v)



Analytes: Pb

Determination of Cd and Pb in biological reference materials by

electrothermal atomic absorption spectrometry: A comparison of three

ultrasonic-based sample treatment procedures

Maduro, C., Valea, G., Alves, S., Galesio, M., Silva, M. D. R. G.,

Fernandez, C., Catarino, S., Rivas, M. G., Mota, A. M. and Capelo, J. L.,

Talanta, 68 (4), 1156-1161, 2006

Abstract

Three different ultrasonic-based sample treatment approaches, the

automated ultrasonic slurry sampling, the ultrasonic assisted acid solid–

liquid extraction (ASLE) and the enzymatic probe sonication (EPS) were

compared and discussed for the determination of Cd and Pb by ET-AAS in

biological reference materials. The sample mass chosen to perform the

analysis was 10 mg and the liquid volume was 1 ml of nitric acid 1M. The

best results were obtained with the slurry procedure with which it was

possible accurate and precise determination of the Cd and Pb content in

four of the five reference materials studied. Optimum performance (total

metal extraction) of ASLE assisted by ultrasound for Cd was only achieved

in two of the four materials assessed whereas total Pb recovery was only

possible in three of the five samples. Total extraction with the enzymatic

probe sonication was only obtained for Cd in oyster tissue. Neither ASLE

nor EPS were able to extract Cd or Pb from spruce needles. Pb

concentration obtained after EPS was found to be highly dependent from

sample centrifugation speed and time.

Type of sample: algae



Sorisole, Italy)


Heating: 1 min at 250 W, 3 min at 0 W, 5 min at 250 W, 5 min at 400 W

and 5 min at 600 W.


Reagents: 3 mL of HNO3 (concentrated) and 0.5 mL of H2O2 30% (m/v)


Detection technique: ET AAS

Analytes: Pb and Cd

Determination of 36 elements in plant reference materials with

different Si contents by inductively coupled plasma mass

spectrometry: comparison of microwave digestions assisted by three

types of digestion mixtures

Sucharová, J. and Suchara, I., Analytica Chimica Acta, 576 (2), 163-176,

2006

Abstract

Closed-vessel microwave digestion of nine standard reference plant

materials (NIST, BCR, IAEA) and a laboratory standard of

plantmaterialwith different Si contents assisted by HNO3+H2O2 (procedure

A), HNO3+H2O2+HF+H3BO3 (procedure B) and HNO3+H2O2+HBF4

(procedure C) were used to determine the recovery of 36 elements by

ICP-MS: Ag, Al, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, In,

La, Li, Mn, Mo, Nd, Ni, Pb, Pr, Rb, Sb, Se, Sn, Sr, Th, Tl, U, V, W, Y, Zn.

Additions of HF+H3BO3 and HBF4 in procedures B and C exceeded by

10% (B1, C1) and 100% (B2, C2) the equivalent concentrations of Si in the

samples determined by ICP-OES. Most recoveries of certified elements

(e.g., Al, Cu, Mo, Rb, Sb, Th) decreased significantly (p ≤ 0.05) with

increasing Si content in plant reference materials digested by procedure A,

while the recoveries from procedures B and C decreased insignificantly

only for Mo and Sb. Digestions B and C gave significantly higher

recoveries of Al, Sb, W and REEs, which were tighter to the reference

values of these elements. A similar effect was found for Cu, Fe, Li, Ni, Sn,

Th, Tl, V, Zn, Ba, Rb and Sr recoveries in samples with Si contents

exceeding 2000 µg/g. If the Si content in plant samples is less than

10 mg/g, digestion of 0.5 g of plant samples through 0.05 mL of HF and

0.5 mL of 4% H3BO3 or 0.1 mL of HBF4 is recommended to get

satisfactory results for most of the elements. For materials with Si content

exceeding 10 mg g−1 the weight of the sample for digestion should be

reduced to 0.25 g. However, the operation of potential interferences should

be taken into account and eliminated through correction equations and

adequate dilution of the samples.

Type of sample: standard reference plant materials

Sample amount: 0.5 g of plant SRMs or 0.25 g for SRMs with a high

concentration of Si


USA)


Heating: a ramp time of 10 min to reach 150 °C and a dwell time of

10 min at 150 °C, both at a pressure limit of 17.0 atm. The power was

1000 W. In procedure B the solution in the closed vessel was then heated in

the microwave oven for 20 min at power 1000 W to reach 190 °C and

pressure 11.5 atm


Reagents: 5 mL HNO3 conc. + 2 mL H2O2 30% (v/v) (procedures A, B and

C) + 0.01 mL HF 48% (v/v) (procedure B) + 0.01 mL H3BO3 4% (m/v)

(procedure B) + 0.015 mL HBF4 48% (procedure C)



Analytes: Ag, Al, As, Ba, Be, Bi, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, In,

La, Li, Mn, Mo, Nd, Ni, Pb, Pr, Rb, Sb, Se, Sn, Sr, Th, Tl, U, V, W, Y and

Zn

Determination of mineral and trace elements in some medicinal herbs

and their infusions consumed in Turkey

Basgel, S. and Erdemoglu, S. B., Science of the Total Environment, 359 (1-

3), 82-89, 2006

Abstract

Fourteen mineral and trace elements (Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg,

Mn, Ni, Pb, Sr and Zn) were determined in the herbs and their infusions

consumed for medical purposes in Turkey such as chamomile (Matricaria

chammomile L.), fennel (Foeniculum vulgare), linden (Tilia vulgaris),

nettle (Urtica dioical), rosehip (Fr. Rosa caninae), sage (Salvia officinalis)

and senna tea (Cassia anqustifolia). Microwave digestion procedure was

applied under optimized conditions for dissolution of medicinal herbs.

Element concentrations in the medicinal herbs and their infusions were

determined by FAAS and ICP-AES. The accuracy and precision were

verified against a GBW 07605 Poplar leaves and Tea certified reference

material. The mineral and trace element content of medicinal herbs and

their infusions showed a wide variability. However, distribution of the

elements in the infusions is not high and it is nil especially for Cd, Co, Cr

and Pb.

Type of samples: medicinal herbs and infusions


Microwave oven (model): HP 500 MARS 5 (CEM Corporation,

Matthews, NC, USA)


Heating: The vessel was closed, placed on the rotating turntable of the

micro wave oven and then digestion was started for 3 min. When the time

finished, the vessel was removed from the oven and cooled to room

temperature. A volume of 4 mL of concentrated HClO4 was added to

previous content of the vessels and digestion was allowed to continue at

400 W for 4 min. After re-cooling, 3 mL of concentrated HCl was added

into the vessel and then the power was gradually increased at 400 W for

2 min, at 550 W for 2 min and 700 W for 4 min. Finally 1 mL of

concentrated HClO4 was added into cooled PTFE vessel for digestion at

700 W for 3 min. Maximum operating pressure was 23.81 atm.


Reagents: 8 mL HNO3 conc. + 4 mL HClO4 conc. + 3 mL HCl conc. +

1 mL HClO4 conc. Pretreatment general aspects: -

Detection technique: F AAS and ICP OES

Analytes: Al, Ba, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sr and Zn

Determination of trace elements in herbal tea products and their

infusions consumed in Thailand

Nookabkaew, S., Rangkadilok, N. and Satayavivad, J., Journal of

Agricultural and Food Chemistry 54 (18), 6939-6944, 2006

Abstract

Nineteen elements, Mg, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Sr, Sb,

Ba, As, Cd, Hg, and Pb, were determined in three types of popular herbal

tea products, Gynostemma pentaphyllum, Camellia sinensis, and Morus

alba. These herbal tea products, both imported and locally made products,

are widely consumed in Thailand and worldwide. Microwave-assisted acid

digestion was used for all of the samples, and the element contents were

determined by ICP-MS. The concentrations of all elements varied among

these herbal teas. Ca and Mg were the most abundant elements in all herbal

samples (1384-34070 and 783-7739 mg/kg, respectively). Most elements in

these herbal tea powders were also released into the infusions at different

percentages depending on types of herbs. G. pentaphyllum infusion

contained essential elements (Mg, Ca, V, and Fe) at higher levels than C.

sinensis and M. alba infusions. Al and Ni were present at high levels in C.

sinensis infusion, and Cd level was high in M. alba infusion. The daily

intake of all elements from these herbal tea infusions (three cups/day) is

still within the average daily intake. Therefore, it may not produce any

health risks for human consumption, if other sources of toxic metal

contaminated food are not taken at the same time.

Type of sample: herbal tea


Microwave oven (model): HP-500 MARS 5 (CEM Corporation,

Matthews, NC, USA)


Heating: 11.5 atm and 190 °C over 30 min and then maintained at 190 °C

for 40 min.


Reagents: 6 mL of concentrated HNO3 and 2 mL of H2O2 30% (m/v)

Pretreatment general aspects: Samples were powdered with a stainless

steel blender.


Analytes: Mg, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Se, Sr, Sb, Ba, As,

Cd, Hg, and Pb

Determination of twenty-five elements in lichens by sector field

inductively coupled plasma mass spectrometry and microwave-assisted

acid digestion

Pino, A., Alimontil, A., Botrè, F., Minoia, C., Bocca, B. and Conti, M. E.,

Rapid Communications in Mass Spectrometry, 21 (12), 1900-1906, 2007

Abstract

A simple and efficient digestion method for rapid sample preparation and

quantification of 25 chemical elements in lichens by sector field

inductively coupled plasma mass spectrometry is described. A microwave

(MW)-assisted acid digestion was carried out at atmospheric pressure

simultaneously handling up to 80 samples in screw-capped disposable

polystyrene tubes. This digestion procedure was compared with the

established MW digestion in closed vessels in order to examine its potential

applicability in routine analysis for environmental monitoring. Three

certified reference materials, i.e. BCR 482 (lichens), BCR 62 (olive leaves)

and BCR 100 (beech leaves), as well as a small set of real samples were

analyzed. Limits of quantification, accuracy and precision of the method

were assessed. The majority of the elements were totally recovered from

the lichens and from the other vegetable matrices. Low contamination risk,

simplicity, time-saving, and applicability in routine analyses make this

method very suitable for use in extensive screening campaigns.

Type of sample: lichens


Microwave oven (model): ETHOS MEGA II equipped with a Multi PREP

80 rotor, Milestone, Sorisole, Italy

Vessel material: Polystyrene and PTFE

Heating: Digestion. A. Step 1: ramp time 30 min, 80 °C. Step 2: 30 min,

80 °C. Step 3: ramp time 10 min, 80-90 °C. Step 4: 120 min, 90 °C.

Digestion. B. Step 1: 250W, 5 min. Step 2: 0W, 5 min. Step 3: 250W,

5 min. Step 4: 600 W, 5 min.

Number of samples simultaneously digested: 80 or 10

Reagents: Digestion. A: 4.0 mL HNO3 + 0.2 mL HClO4 (Cycle I) and

0.1 mL HF + 0.3 mL H3BO3 0.45 mol/L (Cycle II). Digestion. B: 4.0 mL

HNO3 + 0.1 mL HF

Pretreatment general aspects: Dig. A: The samples were previously

soaked with 10% ultrapure HNO3 for 24h and rinsed with deionized water.

A predigestion step overnight at room temperature with 4.0 mL of HNO3

and 0.2 mL of HClO4 was carried out. After the digestion time, samples

were brought to a final volume of 10 mL. Dig. B: After the digestion time,

samples were brought to a final volume of 10 mL.


Analytes: Al, As, Ba, Ca, Cd, Co, Cr, Cs, Cu, Fe, K, Mg, Mn, Mo, Na, Ni,

Pb, Sb, Se, Sn, Sr, Tl, V, W and Zn

Evaluation of different sample extraction strategies for selenium

determination in selenium-enriched plants (Allium sativum and

Brassica juncea) and Se speciation by HPLC-ICP-MS

Bayón, M. M., Molet,, M. J. D., González, E. B. and Medel, A. S., Talanta,

68 (4), 1287-1293, 2006

Abstract

Several sample extraction techniques have been evaluated in order to

obtain highest selenium (Se) extraction efficiency in two types of selenium-

enriched plants (Allium sativum and Brassica juncea). Three extracting

solutions have been studied for this purpose: 0.1 mol/L HCl, 25 mmol/L

ammonium acetate buffer (pH 5.6) and protease in aqueous solution. In

each case, the effect of the ultrasonic probe during extraction was also

evaluated. Selenium extraction yields were calculated based on the ICP-MS

determination of the total selenium content in the corresponding extracts

and in the plant tissue after its microwave digestion. The action of

ultrasounds allowed the reduction on the extraction time while maintaining

good Se recoveries (which ranged from 75 to 120% of the total Se in the

plant). The accuracy of total Se determination was controlled by analyzing

a reference material (aquatic plant, BCR-670). On the other hand,

speciation studies of the extracts were carried out by using ion-pairing

reversed phase and size exclusion/ion exchange (Shodex Asshipak) liquid

chromatographic columns. The two separation mechanisms were suitable to

isolate the main extractable Se species which were identified as Se-methyl

selenocysteine and Se-methionine in both systems. The extracts of both

plants (A. Sativum and B. juncea) exhibited also the presence of several

unknown Se-species.

Type of sample: plants


Microwave oven (model): MLS-1200 (Milestone Corporation, Sorisole,

Italy)




Reagents: 1.5 mL of HNO3 65% (v/v) and 1.5 mL of HF 48% (v/v)

Pretreatment general aspects: Samples were lyophilized at -54 °C during

48 h.

Detection technique: HPLC-ICP-MS

Analytes: Se and organic Se species

Heavy metals from soil and domestic sewage sludge and their transfer

to Sorghum plants

Jamili, M. K., Kazi, T. G., Arain, M. B., Afridi, H. I., Jalbani, N., Menon,

A. R. and Shah, A., Environmental Chemical Letters, 5 (4), 209-218, 2007

Abstract

We studied the mobility and transport of heavy metals such as Cu, Zn, As,

Cd, Cr, Ni, and Pb, from soil and soil amended with sewage sludge to

sorghum plants. The total and ethylenediaminetetraacetic acid (EDTA)

extractable heavy metals in agricultural soil and untreated domestic sewage

sludge (DWS) samples were determined. The correlation between the total

and extractable metals in soil and sewage sludge was investigated. The

total and extractable heavy metals in soil, sewage sludge and sorghum

grain were analysed by flame and electro thermal atomic absorption

spectrometer (FAAS/ETAAS), after digestion in microwave oven.

Statistically good correlations were obtained between the total contents of

all heavy metals and their respective extractable fractions in soil and

domestic wastewater sludge. Transfer factors of all heavy metals from

domestic sewage sludge to sorghum grains were determined.

Type of sample: soil and soil amended with sewage sludge to sorghum

plants




Heating: 30 min, 250 W


Reagents: 4 mL of HNO3 concentred and 2 mL H2O2 30%


Detection technique: FAAS and ETAAS

Analytes: Cu, Zn, As, Cd, Cr, Ni, and Pb

Macro- and micro-nutrients and their bioavailability in polish herbal

medicaments

Lesniewicz, A., Jaworska, K. and Zyrnicki, W., Food Chemistry, 99 (4),

670–679, 2006

Abstract

Several polish herbal medicaments were studied to determine trace

elements and their bioavailable forms by the use of the ICP-AES method.

The contents of Al, B, Ba, Bi, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, P, Pb, Se,

Si, Ti, V and Zn were determined. The total concentrations were measured

in samples mineralised with concentrated nitric acid and hydrogen peroxide

in a microwave system. The one-step extraction was applied, using, as

extractants: deionised water, diluted hydrochloric acid and buffer solution

containing pepsin. Efficiencies of the leaching versus time were

investigated. The extraction efficiencies were analysed, taking into account

bioavailability of elements under conditions simulating digestion processes

in the alimentary system. The contents of the examined elements in

prescribed amounts of medication, were compared to the nutritional

requirements and daily permissible dose. The results are considered in

terms of the utility of the natural herbal medicaments as a source of

minerals indispensable for proper functioning of the human organism.

Some points of merit (precision of measurements, accuracy by Standard

Reference Material analysis) are also considered.

Type of sample: polish herbal medicaments



Sorisole, Italy)


Heating: a six-step programe, with maximum power 650 W was used


Reagents: 6 mL HNO3 conc. + 1 mL H2O2 30% (m/v)


Detection technique: ICP-AES

Analytes: Al, B, Ba, Bi, Ca, Cd, Cr, Cu, Fe, Mg, Mn, Ni, P, Pb, Se, Si, Ti,

V and Zn

Multi-elemental speciation analysis of barley genotypes differing in

tolerance to cadmium toxicity using SEC-ICP-MS and ESI-TOF-MS

Person, D. P., Hansen, T. H., Holm, P. E., Schjoerring, J. K., Hansen, H. C.

B., Nielsen, J., Cakmak, I. and Husted, S., Journal of Analytical Atomic

Spectrometry, 21 (10), 996-1005, 2006

Abstract

Plants respond to Cd exposure by synthesizing heavy-metal-binding

oligopeptides, called phytochelatins (PCs). These peptides reduce the

activity of Cd2+ ions in the plant tissues by forming Cd chelates. The main

objective of the present work was to develop an analytical technique, which

allowed identification of the most prominent Cd species in plant tissue by

SEC-ICP-MS and ESI-TOF-MS. An integrated part of the method

development was to test the hypothesis that differential Cd tolerance

between two barley genotypes was linked to differences in Cd speciation.

Only one fraction of Cd species, ranging from 700–1800 Da, was detected

in the shoots of both genotypes. In the roots, two additional fractions

ranging from 2900–4600 and 6700–15000 Da were found. The Cd-rich

SEC fractions were heart-cut, de-salted and demetallized using reversed-

phase chromatography (RPC), followed by ESI-MS-TOF to identify the

ligands. Three different families of PCs, viz. (γGlu-Cys)n-Gly (PCn), (γGlu-

Cys)n-Ser (iso-PCn) and Cys-(γGlu-Cys)n-Gly (des-γGlu-PCn), the last

lacking the N-terminal amino acid, were identified. The PCs induced by Cd

toxicity also bound several essential trace elements in plants, including Zn,

Cu, and Ni, whereas no Mn species were detected. Zn, Cu and Ni-species

were distributed between the 700–1800 Da and 6700–15000 Da fractions,

whereas only Cd species were found in the 2900–4600 Da fraction

dominated by PC3 ligands. Although the total tissue concentration of Cd

was similar for the two species, the tolerant barley genotype synthesized

significantly more CdPC3 species with a high Cd specificity than the

intolerant genotype, clearly indicating a correlation between Cd tolerance

and the Cd–PC speciation.

Type of sample: plant tissue


Microwave oven (model): Multiwave 3000 (Anton Paar GmbH)


Heating: 30 min (100 ºC), 30 min (50 ºC), 30 min (25 ºC) and 30 min

(50 ºC), which ends up with a total sample preparation time of 150 min,

including three 10 min-ramps between the temperature regimes.


Reagents: 0.75 mL HNO3 70% (v/v) + 8.0 mL H2O

Pretreatment general aspects: The vials with the sample were left

standing overnight for 16 h in a fume-hood, loosely capped.

Detection technique: ESI-TOF-MS

Analytes: Cd

Optimization of microwave assisted digestion procedure for the

determination of zinc, copper and nickel in tea samples employing

flame atomic absorption spectrometry

Soylak, M., Tuzen, M., Souza, A. S., Korn, M. G. A. and Ferreira, S. L. C.,

Journal of Hazardous Materials, 149 (2), 264-268, 2007

Abstract

The present paper describes the development of a microwave assisted

digestion procedure for the determination of zinc, copper and nickel in tea

samples employing flame atomic absorption spectrometry (FAAS). The

optimization step was performed using a full factorial design involving the

factors: composition of the acid mixture (CMA), microwave power (MP)

and radiation time (RT). The experiments of this factorial were carried out

using a certified reference material of tea GBW 07605 furnished by

National Research Centre for Certified Reference Materials, China, being

the metal recoveries considered as response. The relative standard

deviations of the method were found below 8% for the three elements. The

procedure proposed was used for the determination of copper, zinc and

nickel in several samples of tea from Turkey. For 10 tea samples analyzed,

the concentration achieved for copper, zinc and nickel varied at 6.4–13.1,

7.0–16.5 and 3.1–5.7 (µg/g), respectively.

Type of sample: tea


Microwave oven (model): Ethos D, Milestone, Sorisole, Italy


Heating: Steps: 1) 2 min, 250 W. 2) 2 min, 0 W. 3) 6 min, 250 W. 4)

5 min, 400 W. 5) 8 min, 550 W. 6) 5 min, 0 W.


Reagents: 6 mL HNO3 concentred and 2 mL H2O2 concentred



Analytes: Cu, Zn and Ni

Optimisation of sample treatment for arsenic speciation in alga

samples by focussed sonication and ultrafiltration

Salgado, S. G., Nieto, M. A. Q. and Simon, M. M. B., Talanta, 69 (5),

1522-1527, 2006

Abstract

A procedure for arsenic species fractionation in alga samples (Sargassum

fulvellum, Chlorella vulgaris, Hizikia fusiformis and Laminaria digitata) by

extraction is described. Several parameters were tested in order to evaluate

the extraction efficiency of the process: extraction medium, nature and

concentration (tris(hydroxymethyl)aminomethane, phosphoric acid,

deionised water and water/methanol mixtures), extraction time and physical

treatment (magnetic stirring, ultrasonic bath and ultrasonic focussed probe).

The extraction yield of arsenic under the different conditions was evaluated

by determining the total arsenic content in the extracts by ICP-AES.

Arsenic compounds were extracted in 5 mL of water by focussed

sonication for 30 s and subsequent centrifugation at 14.000 x g for 10 min.

The process was repeated three times. Extraction studies show that soluble

arsenic compounds account for about 65% of total arsenic. An

ultrafiltration process was used as a clean-up method for chromatographic

analysis, and also allowed us to determine the extracted arsenic fraction

with a molecular weight lower than 10 kDa, which accounts for about

100% for all samples analysed. Speciation studies were carried out by

HPLC-ICP-AES. Arsenic species were separated on a Hamilton PRP-X100

column with 17 mmol/L phosphate buffer at pH 5.5 and 1.0 mL/min flow

rate. The chromatographic method allowed us to separate the species As

(III), As (V), MMA and DMA in less than 13 min, with detection limits of

about 20 ng of arsenic per species, for a sample injection volume of

100 μL. The chromatographic analysis allowed us to identify As(V) in

Hizikia (46 ± 2 μg/g), Sargassum (38 ± 2 μg/g) and Chlorella

(9 ± 1 μg/g) samples. The species DMA was also found in Chlorella alga

(13 ± 1 μg/g). However, in Laminaria alga only an unknown arsenic

species was detected, which eluted in the dead volume.

Type of sample: algae



USA)


Heating: The digestion was performed during 30 min, applying 15.30 atm

of pressure and 210 °C of temperature




Detection technique: HPLC-ICP-MS

Analytes: As

Rapid, wet oxidation procedure for the estimation of silicon in plant

tissue

Haysom, M. B. and Boczynski, Z. A. O., Communications in Soil Science

and Plant Analysis, 37 (15-20), 2299-2306, 2006

Abstract

The quantification of silicon (Si) in plant samples is being requested more

frequently, especially in agricultural laboratories associated with the

determination of nutritional requirements of sugarcane (Saccharum

officinarum L.) and rice (Oryza sativa L.). The analysis of plant material

for Si can be protracted, especially if laboratories do not have access to X-

ray flourescence (XRF) instrumentation and large numbers of samples are

involved. A simplified procedure using equipment considered standard in

most agricultural laboratories is reported. Dry, ground plant material is

subjected to nitric acid/peroxide oxidation in a low-pressure laboratory

microwave digestion system. The hydrated silica liberated from the organic

matrix is dissolved in a small volume of sodium hydroxide solution also

using the microwave digestion system. Silicon is measured by inductively

coupled plasma atomic emission spectrometry (ICP-AES). This method

gives results that are linearly correlated with the much slower conventional

techniques and avoids using hazardous chemicals (hydrofluoric acid)

sometimes employed in other microwave methods.

Type of sample: sugarcane, rice, and other plants belonging to the

gramineae species.


Microwave oven (model): Anton Paar (model not informed)


Heating: Power settings – acid decomposition: 500 W step to 1000 W for

5 min, maintain at 1000 W. For 10 min, and cool for 15 min at fan setting

2. Power settings – alkali dissolution: 500 W step to 1000 W for 5 min,

maintain at 1000 W for 10 min, and cool for 15 min at fan setting 2.


Reagents: 3 mL HNO3, 2 mL H2O2 and 20 mL NaOH

Pretreatment general aspects: samples were dried at 60 °C and then

ground to pass a 1-mm screen using a microhammer mil.

Detection technique: ICP AES

Analytes: Si

Simultaneous determination of selenium and arsenic contents in

different extracts of Radix Astragali by enhancement effect of ethanol

in hydride generation-inductively coupled plasma-atomic emission

spectrometry

Qiu, P., Ai, C., Lin, L., Wu, J. and Yeh, F., Microchemical Journal, 87 (1),

1-5, 2007

Abstract

A new method was developed for simultaneous determination of trace

arsenic and selenium in different extracts of Radix Astragali by

enhancement effect of ethanol in hydride generation-inductively coupled

plasma-atomic emission spectrometry (HG-ICP-AES) with a microwave

digestion system. The effects of the concentration of the hydride generating

reagent (NaBH4), ethanol concentration, different extraction methods and

pre-reducing reagents on selenium and arsenic emission intensity were

discussed and optimized. The contents of selenium and arsenic in different

extracts (polysaccharide, amino acid, astragaloside, and water decoction,)

in Radix Astragali were analyzed. The proposed method was validated by

the use of two plant reference samples poplar leaf (GBW07604) and tea

(GBW07605). The detection limits (3σ) were 7.0 ng/L and 2.0 ng/L for

Se(IV) and As(III) and relative standard deviations (RSD) were 1.8% and

2.3%, respectively. The determination of selenium and arsenic contents in

different extracts of Radix Astragali would provide useful information for

the quality control of Radix Astragali.

Type of sample: Radix Astragali plant (Astragaloside, polysaccharides and

amino acids)

Sample amount: 0.1 g of each solid sample or 1.0 mL of water decoction

solution

Microwave oven (model): Model XT-III, Shanghai Xintuo Microwave

Rongyang Test Technology Co., Shanghai, China


Heating: Three steps: At the first step the samples were irradiated for 1

min a 0.5 MPa. Second step: 2 min at 1.0 MPa and the third step: 6 min at

2.5 MPa. After digestion, the vessels were cooled in the air to room

temperature before opening for the addition of 1 mL of H2O2. After closure

of the vessels, samples were irradiated for 1 min at 2.5 MPa, and were

cooled to room temperature before measurement.


Reagents: 5 mL HNO3 + 1 mL HF + 1 mL H2O2

Pretreatment general aspects: Radix Astragali plants (200 g) were dried

at 60 °C for 24 h and ground into powder. The powder was stored with

silica gel at room temperature, which stabilized the chemical constituents,

until analysis. For the extraction of total astragaloside, 10 g of ground

powder was extracted with 80% ethanol (100 mL × 2) in an ultrasonic

wave extractor at 60 oC for 1 h. The combined ethanol extract was

concentrated to viscous concentrate on a rotation evaporator. The resulted

viscous concentrate was stirred in 15 mL of 60 oC hot water. The solution

was then loaded on the macroporous resin column and eluted with 150 mL

of 70 % ethanol. Fractions from the column were collected, concentrated,

and freeze dried in lyophilizer. For the extraction of total polysaccharide,

10 g of ground powder was mixed with water (100 mL × 2), decocted by an

ultrasonic wave extractor at 50 oC for 1 h. The water extract was filtered

through a 0.45 μm membrane filter immediately. The filtrate was

concentrated on a rotation evaporator approximately dry. The resulted

concentrate was mixed with 20 mL of 60% ethanol and centrifuged at room

temperature and 4500 r/min, rotation 5 min. The deposition was then dried

under vacuum for seven days. For the extraction of amino acids, 1.0 g of

ground powder was extracted two times with 10 mL of 6 mol/L

hydrochloric acid by an ultrasonic wave extractor at 60 oC for 2 h. The

combined extract solution was concentrated on a rotation evaporator until

approximately dried. The dried substance was re-dissolved in 25 mL of

0.01 mol/L HCl and stored at room temperature until used for the analysis.

Detection technique: HG-ICP-AES

Analytes: Se and As

Total phosphorus and its extratable form in plant drugs. Interrelation

with selected micro-and macroelements

Konieczynski, P. and Wesolowski, M., Food Chemistry, 103 (1), 210-216,

2007

Abstract

Determinations of total phosphorus, its extractable inorganic form and

selected essential elements (Ca, Mg, Na, K, Fe, Zn, Mn, Cu) in 27 leaves of

medicinal plants supplied from the Polish herbal enterprise – Herbapol,

were carried out. After the microwave digestion of plant samples, the total

phosphorus was determined spectrophotometrically, using the

phosphomolybdenum blue method, whereas contents of metals were

established by flame atomic absorption spectrometry (FAAS). Extraction

with 2% (v/v) acetic acid solution was done in order to separate the

extractable inorganic fraction of phosphorus, which was evaluated by the

same method as used for the total elements. The macroelements (P, Ca,

Mg, Na, K) were determined in a range of concentration from several

hundreds of mg/kg to thousands of mg/kg of dry plant tissue.

Microelements (Fe, Zn, Mn, Cu) were found in a range up to several

hundreds of mg/kg of dry plant weight. The average level of the inorganic

fraction of phosphorus represented 63.2% of the total concentration of that

non-metal in leaves, which indicates that a large fraction of phosphorus

may be bioavailable for people who often use herbal teas in their everyday

diet. Statistically significant correlations between the total and extractable

phosphorus and among metals (Ca–Mg, Ca–K, Ca–Fe, Mg–Fe, Cu–K, Cu–

Zn, and Mn–Zn) were observed, concerning their indispensable role in

activation of the same group of enzymes in medicinal plants. PCA

revealed, that the levels of the total, extractable phosphorus and metals,

may depend on the origin of the analyzed leaf sample from plants of the

same plant species.

Type of sample: medicinal plant


Microwave oven (model): Uniclever BM-1z (Plazmatronika, Poland)




Reagents: 5 mL HNO3 + 3 mL H2O2



Analytes: total phosphorus and Ca, Mg, Na, K, Fe, Zn, Mn, Cu

Total and inorganic arsenic in Antarctic macroalgae

Farías, S., Smichowski, P., Vélez, D., Montoro, R., Curtosi, A. and

Vodopívez, C., Chemosphere, 69 (7), 1017-1024, 2007

Abstract

The Antarctic region offers unparalleled possibilities of investigating the

natural distribution of metals and metalloids, such as arsenic. Total and

inorganic As were analysed in nine species of Antarctic macroalgae

collected during the 2002 summer season in the Potter ove area at Jubany–

Dallmann Station (South Shetland Islands, Argentinian Base). Total As was

determined by inductively coupled plasma-optical emission spectrometry

after microwave-assisted acid digestion. Inorganic As was determined by

acid digestion, solvent extraction, flow injection-hydride generation-atomic

absorption spectrometry. Total As ranged from 5.8 µg/g dry weight (dw)

(Myriogramme sp.) to 152 µg/g dw (Himantothallus grandifolius). Total As

concentrations were higher in Phaeophytes (mean ± SD: 71 ± 44 µg/g dw)

than in Rhodophytes (mean ± SD: 15 ± 11 µg/g dw). Inorganic As ranged

from 0.12 µg/g (Myriogramme sp.) to 0.84 µg/g dw (Phaeurus antarcticus).

The percentage of inorganic As with respect to total As was 0.7 for

Phaeophytes, but almost 4 times higher for Rhodophytes (2.6). The work

discusses possible causes for the presence of As in marine organisms in

that pristine environment.

Type of sample: macroalgae


Microwave oven (model): MLS-2000, Milestone-FKW (Sorisole,

Bergamo, Italy)

Vessel material: Teflon-PFA

Heating: Cycle 1: 1) 2 min, 250 W. 2) 2 min, 0 W. 3) 5 min, 250 W. 4)

5 min, 400 W. 5) 5 min, 600 W. Cycle 2: 1) 2 min, 250 W. 2) 2 min, 0 W.

3) 5 min, 250 W. 4) 5 min, 400 W.


Reagents: not informed

Pretreatment general aspects: Inorganis As determination: Deionized

water (4.1 mL) and concentrated HCl (18.4 mL) were added to the samples

(0.5 g) and the mixture was left overnight. After reduction by HBr (2 mL)

and hydrazine sulphate (1.5%, w/v, 1 mL), the inorganic As was extracted

into chloroform (10 mL, 3 times) and back-extracted into 1 mol/L HCl (10

mL, 2 times). Inorganic As in the back-extraction phase was determined by

dry ashing FI–HG–AAS. Calibration standard solutions of As(III),

prepared from As(V) reduced with a mixture of 5% (w/v) KI and 5% (w/v)

ascorbic acid, were used.

Detection technique: ICP OES, ICP MS and FI-HG-AAS

Analytes: Total and inorganic As

Ultrasonic extraction–ozonation sequential Ssmple treatment for the

determination of arsenic in environmental certified reference materials

by hydride generation–atomic fluorescence spectrometry

Costas, C. F., Lavilla, I. and Bendicho, C., Spectroscopy Letters, 39 (6),

713-725, 2006

Abstract

A sample pretreatment method based on ultrasound-assisted extraction

followed by ozonation is developed for sensitive determination of total As

in biological and environmental certified reference materials and an

unknown plant sample (Acacia dealbata) by flow injection and continuous-

flow hydride generation–atomic fluorescence spectrometry. The method is

meant to minimize the use of corrosive and oxidizing acids for sample

decomposition and common errors in trace analysis. Problems derived from

introduction of sonicated extracts in continuous flow and flow injection

manifolds in combination with an atomic fluorescence detector, such as

excessive foaming and flame instability, are addressed. The following

certified reference materials (CRMs) were employed for method

assessment: BCR CRM 482 lichen; BCR CRM 60 and 61 aquatic plants;

BCR CRM 279 sea lettuce; NIST 1633b fly ash; BCR 320 river sediment;

RTC CRM 024-050 soil. Effect of variables such as extraction time,

ultrasound amplitude, concentration of extractant acid, sample mass, drying

mode, and particle size was investigated. Leaves of Acacia dealbata were

also employed for method development. Limits of detection ranged from

0.03 to 0.15 μg/g As depending on the sample. Between-batch precision

values ranged from 2% to 11%. Sample throughput was 40 h-1 with flow

injection.

Type of sample: leaves



USA)


Heating: two stages of 1 min at 2.72 and 5.44 atm, respectively, and a final

stage at 0.008 atm for 5 min; the power used was 300 W.


Reagents: 5 mL of HNO3 conc. and 0.5 mL of HF conc.

Pretreatment general aspects: Leaves were washed with a chloroform-

water (1:1) solution for 10 s, rinsed three times with deionized water, and

dried. Once dried, leaves were ground with a mixer mill equipped with

agate balls for 5 min.

Detection technique: HG-AFS

Analytes: Arsenium

Comparison of atomic absorption, mass and X-ray spectrometry

techniques using dissolution-based and solid sampling methods for the

determination of silver in polymeric samples

Schrijver, I., Aramendia, M., Vincze, L., Resano, M., Dumoulin, A. and

Vanhaecje, F., Spectrochimica Acta Part B, 62 (11), 1185-1194, 2007

Abstract

In this work, the capabilities and limitations of solid sampling techniques –

laser ablation inductively coupled plasma mass spectrometry

(LA-ICP-MS), wavelength dispersive X-ray fluorescence spectrometry

(WD-XRFS) and solid sampling electrothermal atomic absorption

spectrometry (SS-ETAAS) – for the determination of silver in polymers

have been evaluated and compared to those of acid digestion and

subsequent Ag determination using pneumatic nebulization ICP-MS

(PN-ICP-MS) or flame AAS (FAAS). In a first stage, two dissolution

procedures were examined: conventional acid digestion in a Kjeldahl flask

and the combination of dry ashing and microwave-assisted digestion.

Accurate results for Ag could be obtained, although occasionally, problems

of analyte losses and/or incomplete dissolution were observed. LA-ICPMS

shows potential for direct analysis of solid materials, but calibration was

found to be difficult. A polypropylene sample was used as standard. This

approach provided satisfactory results for other polypropylene samples and

even for other types of plastics, provided that the 13C+ signal was used as

internal reference, correcting for variations in ablation efficiency. However,

the results for polyoxymethylene were overestimated. Similar calibration

problems appeared with WD-XRFS, due to differences in absorption

efficiency of X-rays. In this case, the accuracy could be improved by using

a matrix correction procedure, which however required the matrix

composition to be known into sufficient detail. SS-ETAAS, proved to be a

fast approach that allowed accurate determination of Ag in polymers using

aqueous standard solutions for calibration. Due to the high Ag content and

the excellent sensitivity, the use of a 3-field mode Zeeman-effect

background correction system was essential for the extension of the

working range.

Type of sample: polymers: polypropylene (HPPP), acrylonitril butadiene

(ABS), nitrile rubber (NBR) and polyoxymethylene (POM)


Microwave oven (model): MLS-1200


Heating: 1 min at 250 W; 1 min at 0 W; 4 min at 250 W; 4 min at 400 W;

4 min at 600 W; 5 min ventilation


Reagents: 4 mL HNO3 14 mol/L + 1 mL HF 28 mol/L

Pretreatment general aspects: The samples were ashed in a muffle

furnace for one hour at a temperature of 750 ºC before the microwave

digestion.

Detection technique: PN-ICP-MS, FAAS, ETAAS, LA-ICP-MS, WD-

XRFS

Analytes: Ag

New REE and trace element data on two kimberlitic reference

materials by ICP-MS

Roy, P., Balaram, V., Kumar, A., Satyanarayanan, M. and Rao, T. G.,

Geostandards and Geoanalytical Research, 31 (3), 261-273, 2007

Abstract

Data on thirty-four minor and trace elements including all rare earth

elements (REE) are reported for two kimberlitic international reference

materials (SARM-39, MINTEK, RSA and MY-4, IGEM, Russia) by

inductively coupled plasma-mass spectrometry (ICP-MS), some of them

for the first time. Four digestion techniques (open acid, closed vessel acid,

microwave and lithium metaborate fusion digestion) were used for the

decomposition of samples for analysis by ICP-MS. Three other reference

materials (USGS BHVO-1, CRPG BR-1 and ANRT UB-N) were analysed

simultaneously using the same analytical methodology to assess the

precision and accuracy of the determinations. The data obtained in this

study compare well with working values wherever such values are

available for comparison. Though open acid digestion was found to be very

rapid, effective and convenient for the determination of several trace

elements in kimberlitic samples, recoveries for heavy rare earth elements

(HREE) were lower than the respective recoveries obtained by the other

decomposition techniques used. The precision obtained was better than

± 6% RSD in the majority of cases with comparable accuracy. Chondrite-

normalised plots of each RM for all the digestion techniques were smooth.

The new data reported on the two kimberlitic reference materials make

these samples useful for future geochemical studies of kimberlitic rocks.

Type of sample: Six reference materials of rocks



USA)

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Vessel material: PTFE Teflon beakers (Open acid digestion method);

Savillex®Teflon pressure decomposition vessels (Closed vessel digestion

method) and Perfluoro-Alkoxy (PFA) lined vessels that included a safety

rupture membrane (Microwave digestion)

Heating (Pressure and temperature): Open acid digestion method: the

beakers were heated on a hot plate at ~ 200 °C for about 1 hour, the lids

were removed and the contents were evaporated to incipient dryness until a

crystalline paste was obtained. The remaining residues were then dissolved

using 10 mL of 1:1 HNO3 and kept on a hot plate for 10 minutes with

gentle heat (70 °C) to dissolve all suspended particles.

Closed vessel digestion method: the vessels were tightly closed and kept

on a hot plate at ~ 110 °C for 48 hours. Following this, the vessels were

opened and the contents were evaporated at 200 °C for about one hour to

near dryness. The remaining residues were dissolved by adding 10 mL 1:1

HNO3 and kept on a hot plate for 10 minutes to dissolve all suspended

particles.

Microwave digestion: not informed


Reagents: Open acid digestion method: 10 mL an acid mixture HF-HNO3-

HClO4 (7:3:1); Closed vessel digestion method: 10 mL an acid mixture HF-

HNO3-HCl (7:3:2); Microwave digestion: 10 mL an acid mixture HF-

HNO3 (7:3)



Analytes: Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Cs, Ba, La,

Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, Pb, Th, U

A comparative study of acid-extractable and total digestion methods

for the determination of inorganic elements in peat material by

inductively coupled plasma-optical emission spectrometry

Yafa, C. and Farmer, J. G., Analytica Chimica Acta, 557 (1-2), 296-303,

2006

Abstract

In the absence of a standard wet preparation method for the determination

of inorganic elements in peat, four acid digestion methods (nitric acid

(HNO3), HNO3/HCl, aqua regia and HNO3/HF) were compared using a

Canadian fen peat (OGS 1878 P-6), previously proposed as a reference

material, and inductively coupled plasma-optical emission spectrometry

(ICP-OES) as the instrumental analytical technique. Two microwave-

assisted methods, HNO3 and HNO3/HF, representing ‘acid-extractable’ and

total digestion, respectively, were then selected for optimisation and

application to a newly developed ombrotrophic peat reference material

(NIMT/UOE/FM/001) and to the individual sections of a 43 cm peat core,

also from Flanders Moss, Scotland, for a range of elements, including Al,

Co, Cr, Cu, Fe, Mn, P, Pb, S, Ti, V and Zn. While the results suggested the

general efficacy of HNO3 in investigations of the greatly elevated levels of

trace elements, such as Cu, Pb and Zn, resulting from the severe

anthropogenic contamination of the environment during the industrial era,

the need for addition of HF for the determination of major lithogenic

elements, such as Al and Ti, present in aluminosilicates and other resistant

minerals, and some trace elements (Co, Cr and V) was clearly

demonstrated. The inclusion of HF in a total digestion method, such as

HNO3/HF, is, therefore, necessary when normalisation of trace element

concentrations to those of a conservative lithogenic reference element, such

as Ti, is performed for the purpose of determining elemental enrichment



factors. For elements other than Hg, the dry ashing of peat samples at

450 ◦C prior to acid digestion is recommended for the destruction of the

predominantly organic matrix, especially relevant where inductively

coupled plasma-mass spectrometry (e.g. quadrupole inductively coupled

plasma-mass spectrometry (ICP-MS)) is to be used in the determination of

the much lower concentrations of trace elements prevalent in pre-industrial

and ancient times.

Type of sample: peat material



USA)


Heating: (the procedures were adapted from USEPA 3051, 3051a and

3052 protocol) Procedure 1 (10 mL of concentrated HNO3): maximum

power 1200 W, 100%, ramp 30 min, hold 20 min, 10.20 atm, 205 °C; upon

cooling, the solution was filtered through Whatman No. 542 filter paper to

remove any remaining solid material; the solution was evaporated to

approximately 1 mL on a hotplate and then made up to 25 mL with 2%

(v/v) HNO3 prior to analysis by ICP-OES.


Reagents: Procedure 1: 10 mL HNO3 conc. Procedure 2: 9 mL HNO3 conc.

+ 3 mL HCl conc. Procedure 3: 9 mL HNO3 conc. + 0.5 mL HF conc.

Pretreatment general aspects: a representative sample of up to 0.25 g

(initial weight) was ashed at 450 ◦C for 4 h prior to digestion procedures.


Analytes: Al, Co, Cr, Cu, Fe, Mn, P, Pb, S, Ti, V and Zn.

Analysis of environmental samples using microwave-assisted acid

digestion and inductively coupled plasma mass spectrometry:

maximizing total element recoveries

Hassan, N. M., Dabek-Zlotorzynska, R. E., Celo, V. and Chen, H., Water

Air Soil Pollut, 178 (1-4), 323–334, 2007

Abstract

For the routine determination of metals in environmental samples, we

require microwave-assisted digestion methods that yield ‘total’ or ‘near-

total’ recoveries while avoiding the use of HF acid. As inductively coupled

plasma mass spectrometry (ICPMS) is the method of detection, it is

desirable to minimize the use of HCl to avoid spectral interferences caused

by high Cl – concentrations. Using certified reference materials, we

performed a series of modifications to the US EPA method 3051 which

included: increasing the temperature and durations of microwave digestion,

varying the ratio of sample mass to acid volume, and alterations to the

compositions of the acid digestion mixture. The experiments were

conducted using urban particulate matter (NIST- 1648), coal fly ash (NBS-

1633) and six CANMET certified reference materials (Till-2, Till-3, Till-4,

LKSD-1, LKSD-2 and LKSD-4), in two laboratories (Health Canada and

Environment Canada) using different microwave digestion systems and

different ICP-MS instruments. Our modified microwave assisted nitric acid

digestion method improved recoveries for Pb, Zn, V, Fe and Cu

approaching ‘total’ recoveries in the same matrices determined using Xray

fluorescence (XRF) and instrumental neutron activation analysis (INAA) as

reported in the certificates of analysis. Recoveries for other elements such

as Cr and Ni compared well with ‘near-total’ recoveries yielded by

traditional (non-assisted) acid digestion methods.

Type of sample: soil and sediments


Microwave oven (model): Milestone Ethos Touch Control (ETHOS TC)

(24010 Sorisole (Bergamo), Italy) and Model CEM MARS 5 (CEM


Vesselmaterial: Teflon

Heating: ETHOS TC Microwave: ramp time 30 min, hold time 30 min and

hold temperatures 220 oC

MARS 5 Microwave: ramp time 5.5 min, hold time 10 min and 175 oC

Number of samples simultaneously digested: ETHOS TC Microwave: 10

vessels. MARS 5 Microwave: 14 vessels.

Reagents: HNO3 and HCl


Detection technique: ICP MS

Analytes: Pb, Zn, V, Fe, Cr, Ni and Cu

Arsenic release from iron rich mineral processing waste: Influence of

pH and redox potential

Al-Abed, S. R., Jegadeesan, G., Purandare, J. and Allen, D., Chemosphere,

66 (4), 775-782, 2007

Abstract

This paper presents the effect of pH and redox potential on the potential

mobility of arsenic (As) from a contaminated mineral processing waste.

The selected waste contained about 0.47 g/kg of As and 66.2 g/kg of Fe.

The characteristic of the waste was identified by acid digestion, X-ray

diffraction and sequential extraction procedures. Less than 2% of the total

As was acid extractable with the remaining 98% associated with Fe-

oxyhydroxides and oxides. Batch leaching tests at different pH conditions

showed a strong pH dependence on arsenic and iron leaching. Arsenic

leaching followed a "V" shaped profiles with significant leaching in the

acidic and alkaline pH region. Acid extractable phases dissolved at acidic

pH, while desorption of arsenic due to increase in pH resulted in high

arsenic concentration at alkaline pH. Under aerobic conditions and pH 7,

As solubility was low, probably due to its precipitation on Fe-

oxyhydroxides. Maximum As solubilization occurred at pH 11

(3.59 mg/L). Similarity in the As and Fe leaching profiles suggested that

the release of As was related to the dissolution of Fe in the low pH region.

In general, redox potential did not play a significant role in arsenic or iron

solubilization. It was thus concluded that for this solid waste, desorption

was the predominant mechanism in arsenic leaching. A simple

thermodynamic model based on arsenic and iron redox reactions was

developed to identify the more sensitive redox couple.

Type of sample: mushrooms and the underlying soils.



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Vesselmaterial: not informed



Reagents: HNO3 concentred

Pretreatment general aspects: samples were air-dried

Detection technique: ICP-OES.

Analytes: As, Fe.

Comparison of sample digestion procedures for the determination of

arsenic in bottom sediment using hydride generation AAS

Loska, K. and Wiechula, D., Microchimica Acta, 154 (3), 235-240, 2006

Abstract

Certified reference materials (JMS-2 and JMS-1 Marine sediment, LKSD-1

Lake Sediment, and STSD-1 Stream Sediment) and bottom sediment were

analyzed for arsenic by hydride generation atomic absorption spectrometry

(HG-AAS) after digestion by different methods (microwave digestion,

digestion in aluminium block, dry digestion) and different combinations of

acids (HNO3, HCl, HClO4, H2SO4). The study revealed that both wet and

dry digestion can be used to digest the reference materials and bottom

sediment. Exceptionally satisfactory results were produced by the

application of aqua regia, HNO3+HCl+HClO4, and HNO3+HCl mixtures.

Addition of Mg(NO3)2 during dry digestion caused an increase in arsenic

recovery in the reference materials and improved the accuracy of arsenic

determination in the bottom sediments.

Type of sample: sediment



Sorisole, Italy)


Heating: 3 min at 250 W, 1 min at 0 W, 2 min at 450 W, 4 min at 650 W,

3 min at 950 W and 1 min at 0 W.


Reagents: HNO3, HCl and HClO4, at different ratio volumes

Pretreatment general aspects: The samples were ground and dried.

Detection technique: HG AAS

Analytes: As

Determination of alkylated tin compounds in landfill leachates using

isotopically enriched tin species with GC-ICP-MS detection

Pinel-Raffaitin, P., Rodriguez-Gonzalez, P., Ponthieu, M., Amouroux, D.,

Le Hecho, I., Mazeas, L., Donard, O.F.X. and Potin-Gautier, M., Journal of

Analytical Atomic Spectrometry, 22 (3), 258-266, 2007

Abstract

A method for the simultaneous determination of methylated, ethylated and

butylated tin compounds in landfill leachates has been developed in this

work. The assessment of the organotin compound composition has been

achieved by the development of a specific GC-ICP-MS protocol adapted to

these complex matrices. The analytical procedure consists in three major

steps which have been carefully optimized, taking into account the variety

of alkyltin compounds and the high organic content of the leachate matrix:

nitric acid digestion under microwave, derivatization using sodium

tetrapropylborate and chromatographic separation. Different quantification

approaches are proposed for the determination of the alkyltin species in the

leachates. In this way, isotope dilution analyses in the species-specific and

species-unspecific spiking modes have been found to provide results in

agreement with external and internal calibration approaches. A single

analysis with an addition of three isotopically enriched butyltin species is

found to be suitable for the routine quantitative and semi-quantitative

determination of all occurring alkyltin species in landfill leachates. The

different qualitative and quantitative GC-ICP-MS complementary

approaches developed in this work allow the full organotin composition

assessment of landfill leachates.

Type of sample: landfill leachates

Sample amount: 5 mL

Microwave oven (model): An open focused vessel microwave oven

Prolabo A301 (France)

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Reagents: concentrated nitric acid


Detection technique: Gas chromatography coupled to inductively coupled

plasma mass spectrometry (GC-ICP-MS)

Analytes: methylated, ethylated and butylated tin compounds

Metal speciation in coastal marine sediments from Singapore using a

modified BCR-sequential extraction procedure

Cuong, D. T. and Obbard, J. P., Applied Geochemistry, 21 (8), 1335-1346,

2006

Abstract

The chemical speciation of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in

marine sediments from two coastal regions of Singapore (Kranji in the

NW, and Pulau Tekong in the NE) was determined using the latest version

of the 3-step sequential extraction procedure, as described by the European

Community Bureau of Reference (1999). To obtain a mass balance, a

fourth step, i.e., digestion and analysis of the residue was undertaken using

a microwave-assisted acid digestion procedure. The total content of all

metals except for Pb in sediments was greater in Kranji than in Pulau

Tekong. All metals, except Cd were more mobile and bio-available in

Kranji, where metals were present at higher percentages in the acid-soluble

fractions (the most labile fraction). In sediments from Kranji, the mobility

order of the heavy metals studied was Cd > Ni > Zn > Cu > Pb > Cr,

whereas sediments from Pulau Tekong showed the same order for Cd, Ni,

Pb and Cr, but had a reverse order for Cu and Zn (Cu > Zn). The highest

percentages of Cr, Ni and Pb were found in the residual fractions in both

Kranji (78.9%, 54.7%, 55.9%, respectively) and Pulau Tekong (82.8%,

77.3%, 62.2%, respectively), meaning that these metals were strongly

bound to the sediments. Results are consistent with findings from

Barcelona, Spain where similar results for Cr and Ni have also been

reported for marine sediments. The sum of the 4 steps (acid-soluble +

reducible + oxidizable + residual) was in good agreement with the total

content, which implies that the accuracy of the microwave extraction

procedure in conjunction with the GF AAS analytical method is assured.

Type of sample: marine sediments


Microwave oven (model): microwave unit MARS 5, CEM Corporation,

Matthews, NC, USA

Vessel material: PP, HDPE or PTFE

Heating: Samples were heated in the microwave unit. The temperature of

samples rose to 180 ± 5 °C in 10 min and remained at 180 ± 5 °C for

9.5 min. Digests were centrifuged at 3000 rpm for 10 min to clear the

supernatant.


Reagents: 9 mL HNO3 conc. + 3 mL HF conc.



Analytes: Cd, Cr, Cu, Ni, Pb and Zn

Optimisation of microwave assisted digestion of sediments and

determination of Sn and Hg

Navarro, P., Raposo, J. C., Arana, G. and Etxebarria, N., Analytica

Chimica Acta, 576 (1), 37-44, 2006

Abstract

The determination of Sn by flow injection–hydride generation–quartz

furnace atomic absorption spectrometric (FI–HG–QFAAS) was optimised

following different experimental designs. The best conditions were: 0.2%

HCl (v/v), 0.5% NaBH4 (w/v) and the furnace temperature 875 ◦C. Under

those conditions, the limit of detection was 0.17 ng/dm3 and a precision of

5.3% was obtained. One of the aims of this work was to optimise the closed

vessel microwave assisted digestion (MAD) of sediments for the

determination of Sn and Hg in the same extract using the analytical

conditions previously optimised for Sn in the FI–QFAAS. The optimisation

of the MAD of sediments was accomplished following a D-optimal design,

including the composition of the HCl–HNO3 mixture, the pressure and

irradiation time. However, we could not determine tin in the extracts due to

the formation of foams, the optimisation of the digestion conditions were

taken from the FI–cold vapour (CV)–QFAAS measurements of mercury.

The optimum conditions were: 2.1 bar of pressure during 10 min of

irradiation and two local optima composition of the acid mixtures: 80%

HCl–20% HNO3 and 60% H2O–20% HCl–20% HNO3. The determination

of mercury in sediments was validated with the CRM-580. In order to

determine Sn in sediments the solutions from the same D-optimal design

were analysed using an ICP-MS and the digestion conditions were

optimised for Sn and for other 8 metals. In this case the same optimal

conditions were obtained (2.1 bar and 10 min) but different acid mixture

composition 20% HCl–80% HNO3. The determination of Sn and the other

metals in sediments was validated using two other CRMs (PACS-2 and

SGR-1).

Type of sample: sediments


Microwave oven (model): MDS 2000 (CEM Corporation, Matthews, NC,

USA)


Heating: the irradiation process was divided in two parts: firstly, the oven

worked at full power (630 W) in order to reach the expected pressure

according to the experimental design; and secondly, the pressure was kept

constant at 80% of power during the time of the experiment (10 min

irradiation time and maximum pressure 2.04 atm).

Number of samples simultaneously digested: -

Reagents: 3 mL HNO3 20% (v/v) + 3 mL HCl 80% (v/v) + 9 mL H2O or

12 mL 20% (v/v) HCl + 3 mL HNO3 20% (v/v)


Detection technique: FI-CV-QF AAS and FI-HG-QF AAS (additional

elements were determined by ICP-MS)

Analytes: Hg and Sn (Cd, Ce, Co, Cr, Cu, Mn, Pb, Sn, V and Zn were also

determined)

Toxic elements at a disused mine district: Particle size distribution and

total concentration in stream sediments and mine tailings

Giuliano, V., Pagnanelli, F., Bornoroni, L., Toro, L. and Abbruzzese, C.

Journal of Hazardous Materials, 148 (1-2), 409–418, 2007

Abstract

Heavy metal and metalloid pollution at a disused pyrite mine was

investigated. Five solid samples collected in the area (three stream

sediments with different soil texture, a background soil sample and a mine

tailing) were characterised by mineral and element composition, particle

size distribution (by wet and dry sieving and laser diffraction) and total

concentration by acid digestion (Mn, Zn, Cu, Pb, Hg, Cd, Sb and As).

X-ray and element analyses denoted a common mineralogical and chemical

composition of mainly quartz, clinochlore, muscovite, anorthite, and

hematite. Particle size distributions of the five samples showed that stream

sediments were characterised by larger percentage of sand range classes

(2000–60 µm) while background sample and tailing are mainly

characterised by gravel particles (> 2000 µm).Wet and dry sieving

procedures gave different particle size distributions, which can be

interpreted by laser diffraction analysis and represented by Rosin–Rammler

model. Concentrations of Zn, Cu and Cd were higher in the stream

sediments than the tailing and background soil, while Mn, As, Sb and Hg

are mainly concentrated in the tailing sample. Metal concentrations in the

three stream sediment samples are correlated with both particle size

dimensions (D 63.2) and concentration of geochemical normalizers (iron and

aluminium). These correlations are observed also for the pollutants that are

mainly concentrated in tailing sample (Mn and As), denoting the

importance of surface interactions also for the binding of these elements

onto stream sediments.

Type of sample: stream sediments, soils and mine tailings.




Heating: Step 1: 800 W, 4 min. Step 2: 400 W, 4 min. Step 3: 800 W, 4

min. Step 4: 20 min of ventilation. After complete digestion of solid

samples, 5.6 g HBO3 was added to avoid silica evaporation and each liquid

sample was diluted to 100 ml with deionized water.


Reagents: 3 mL HNO3 65% + 1 mL HCl 37% + 6 mL HF 48%


Detection technique: ICP- MS

Analytes : As, Cd, Cu, Hg, Mn, Pb, Sb and Zn.

A rapid fractionation method for heavy metals in soil by

continuous-flow sequential extraction assisted by focused microwaves

Nakazato, T., Akasaka, M., and Tao, H., Analytical and Bionalytical

Chemistry, 386 (5), 1515-1523, 2006

Abstract

A microwave-assisted continuous-flow sequential extraction system was

developed for rapid fractionation analysis of heavy metals in soil. Insertion

of pressure-adjusted air between the extractants provided stable flows of

the extractants without mutual mixing and back-pressure influence of a

column packed with soil, thereby facilitating reliable continuous-flow

extractions. In addition, use of pure water as a pumping solvent removed

metal contamination because of direct contact between corrosive

extractants and the pump containing metallic materials. Focused

microwave irradiation to the soil accelerated the selective extractions of the

acid-soluble and reducible fractions of heavy metals in soil in the first and

second steps of the sequential extraction conditions, as defined by the

Commission of the European Bureau of Reference (BCR). The microwave-

assisted continuous-flow extraction provided high correlations in amounts

of six heavy metals except Zn in the first step and Cu in the second step

extracted from a reference sludge soil, BCR CRM 483, with a conventional

batchwise extraction proposed by BCR; continuous-flow extraction assisted

by conductive heating provided lower correlations for all the six metals.

The proposed method drastically reduced the time required for the

sequence extraction to ca. 65 min without losing accuracy and precision of

the fractionation analysis of heavy metals in soil, whereas the BCR

batchwise method requires ca. 33 h.

Type of sample: Soil



Microwave oven (model): focused-microwave irradiator Discover (CEM


Vessel material: PEEK columm

Heating: Optimized flow rate conditions of the extractant and microwave

power for step 1 were 0.1 mL/min and 40 W; those for step 2 were

0.15 mL/min and 10 W, respectively. The step 3 extraction was

successively performed without microwave irradiation.


Reagents: acetic acid + hydroxylammonium chloride + nitric acid +

hydrogen peroxide + ammonium acetate



Analytes: Cu, Cd, Cr, Ni, Pb, Pb, Zn and Cl

Calibration of an HPGe detector and self-attenuation correction for 210Pb: Verification by alpha spectrometry of 210Po in environmental

samples

Saidou, F. B., Laedermann, J. P., Buchillier, K. N. M and Froidevaux, P.,

Nuclear Instruments and Methods in Physics Research, 578 (3), 515-522,

2007

Abstract

In this work the calibration of an HPGe detector for 210Pb measurement is

realised by a liquid standard source and the determination of this

radionuclide in solid environmental samples by gamma spectrometry takes

into account a correction factor for self-attenuation of its 46.5 keV line.

Experimental, theoretical and Monte Carlo investigations are undertaken to

evaluate self-attenuation for cylindrical sample geometry. To validate this

correction factor, 210Pb (at equilibrium with 210Pb) alpha spectrometry

procedure using microwave acid digestion under pressure is developed and

proposed. The different self-attenuation correction methods are in

coherence, and corrected 210Pb activities are in good agreement with the

results of 210Po. Finally, self-attenuation corrections are proposed for

environmental solid samples whose density ranges between 0.8 and 1.4

g/cm3 and whose mass attenuation coefficient is around 0.4 cm2/g.

Type of sample: soil

Sample amount: 1 g

Microwave oven (model): Milestone MLS Ultra Clave, (Milestone,

Sorisole, Italy)


Heating: Samples were heated in the microwave oven at 170 oC for 40 min

at a loading pressure of 60 bar.


Reagents: 30 mL HNO3 concentred + 1 mL 209Po

Pretreatment general aspects: After filtration and dry evaporation at 80–

90 oC, being cautious to avoid temperatures above 100 oC to minimise

losses of polonium by volatilization, the residue was dissolved in 40 mL of

2 mol/L HCl.

Detection technique: Canberra Alpha Analyst spectrometer

Analytes: 210Pb

Closed vessels microwave digestion method for uranium analysis of

soils using alpha-spectroscopy

Amoli, H. S., Barker, J. and Flowers, A., Journal of Radioanalytical and

Nuclear Chemistry, 273 (2), 281-284, 2007.

Abstract

This paper describes our development of an accurate determination of

uranium by alpha spectrometry using various kinds of sample digestion

methods. The sample preparation techniques employed an acid digestion

with HNO3, and microwave oven digestion either by HNO3 or by

combination of HNO3 and HF. The samples were obtained from surface

and in depth (40 cm) soils from residential area. An extraction

chromatography column has been used to separate the uranium from

interference matrix and elements. Results show that the microwave method

significantly speeds up the analysis time, reduces the volume of acids used

and eliminates a large fraction of acid vapour emission. Compared with the

uranium recoveries it was shown that microwave HNO3+HF achieved

greater recovery (83%) than microwave HNO3 (78%), while less obtained

by HNO3 digestion using hot plate (75%). Various kind of digestion

methods have been applied (24 times) for two kind of soil sample. The

reproducibility was acceptable and the average precision (coefficient of

variation) was between 4 to 5. No significant differences between the

precision of the methods have been observed. Acid volume required for the

microwave procedures are a fraction of 5 times lower and the analysis time

6 times lower than traditional digestion by hot plate technique.

Type of sample: soils


Microwave oven (model): (Model MDS- 2100), CEM Corporation,

Matthews, NC, USA)


Heating: Digestion 1 (HNO3): step 1) 30 min, 8.16 atm. Digestion 2

(HNO3): step 1) 30 min, 8.16. Step 2) HF was added to each sample soil

and left for 24 hours.


Reagents: Digestion 1: 10 mL HNO3. Digestion 2: 10 mL HNO3 + 10 mL

HF.

Pretreatment general aspects: Soil samples were air dried and after

sieving through 2 mm plastic mesh were also oven dried for 24 hours at

110 °C.

Detection technique: Alfa- spectrometer

Analytes: U

Copper, zinc, and cadmium accumulation in two prairie soils and

crops as influenced by repeated applications of manure

Lipoth, S. L. and Schoenau, J. J., Journal of Plant Nutrition and Soil

Science, 170 (3), 378-386, 2007

Abstract

A study was conducted to determine the effect of repeated (5-7 y) annual

application of liquid swine or solid cattle manure on the plant availability

of copper (Cu), zinc (Zn), and cadmium (Cd) at two field sites in the W-

central and E-central agricultural regions of Saskatchewan, Canada. Soil

samples, plant-straw and grain samples from the 2003 growing season were

collected and analyzed for total Cu, Zn, and Cd concentrations using nitric

acid microwave digestion followed by atomic-absorption spectroscopy. An

ammonium bicarbonate diethylenetriaminepentaacetic acid (AB-DTPA)

extraction was performed on the soil samples as a measure of the plant-

available fraction. Crop plants that were tested included wheat (Triticum

aestivum L.) and barley (Hordeum vulgare L.). The results of this study

indicated that long-term repeated applications of manure fertilizer

sometimes resulted in increased plant availability of Cu, Zn, and Cd, as

reflected in increased concentrations of the plant-available metal observed

both in the soil and plant tissue. In the case of Cu and Zn, these increases

were related to the rate of application, as the manure is a source of Cu and

Zn. Changes in soil conditions from repeated manure application, including

a decrease in pH and stimulated plant-root growth can explain the effect

that both manure and urea-fertilizer application had on increasing the Cd

concentration in the plant. Overall, there does not appear to be any concern

about soil metal loading and plant accumulation in these soils after 5-7 y of

manure application, as soil and plant concentrations were well below the

allowable limits.

Type of sample: soil and plants

Sample amount: soil: 1 g, plant: 0.5 g

Microwave oven (model): Model MDS-2000 (CEM Corporation,

Matthews, NC, USA)


Heating: soil: 90% power in two stages, pressure was maintained at each

stage for 10–15min. Plant: 90% power in three stages


Reagents: 10 mL HNO3

Pretreatment general aspects: after digestion time the digests were

diluted to 50 mL.


Analytes: Cu, Zn and Cd

Observation: the air dried-soil was extracted using 40 mL AB-DTPA in

20 g of soil. The mixture was shaken for 15 min at 180 cycles/min. the

extracts were then filtered through WhatmanTM with suction applied.

CZE for the speciation of arsenic in aqueous soil extracts

Kutschera, K., Schmidt, A. C., Kohler, S. and Otto, M., Electrophoresis, 28

(19), 3466-3476, 2007

Abstract

We developed two separation methods using CZE with UV detection for

the determination of the most common inorganic and methylated arsenic

species and some phenylarsenic compounds. Based on the separation

method for anions using hydrodynamic sample injection the detection

limits were 0.52, 0.25, 0.27, 0.12, 0.37, 0.6, 0.6, 1.2 and 1.0 mg/L As for

phenylarsine oxide (PAO), p-aminophenylarsonic acid (p-APAA), o-

aminophenylarsonic (o-APAA), phenylarsonic acid (PAA), 4-hydroxy-3-

nitrobenzenearsonic acid (roxarsone), monomethylarsonic acid (MMA),

dimethylarsinic acid (DMA), arsenite or arsenious acid (AsIII) and arsenate

(AsV), respectively. These detection limits were improved by large-volume

sample stacking with polarity switching to 32, 28, 14, 42, 22, 27, 26 and

27 mg/L As for p-APAA, o-APAA, PAA, roxarsone, MMA, DMA, AsIII

and AsV, respectively.We have applied both methods to the analysis of the

arsenic species distribution in aqueous soil extracts. The identification of

the arsenic species was validated by means of both standard addition and

comparison with standard UV spectra. The comparison of the arsenic

species concentrations in the extracts determined by CZE with the total

arsenic concentrations measured by inductively coupled plasma-atomic

emission spectroscopy (ICP-AES) indicated that CZE is suited for the

speciation of arsenic in environmental samples with a high arsenic content.

The extraction yield of phenylarsenic compounds from soil was derived

from the arsenic concentrations of the aqueous soil extracts and the total

arsenic content of the soil determined by ICP-AES after microwave

digestion. We found that 6–32% of the total amount of arsenic in the soil

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was extractable by a one-step extraction with water in dependence on the

type of arsenic species.



Microwave oven (model): MLS Start 1500 (MLS, Leutkirch, Germany)


Heating: 120 °C in 5 min and to 200 °C in the following 5 min; this

temperature was held constant for further 10 min


Reagents: 2 mL HNO3 65% + 6 mL HCl 32% + 2 mL H2O



Analytes: As

Evaluation of extraction/digestion techniques used to determine lead

isotopic composition in forest soils

Komárek, M., Chrastný, V., Ettler, V. and Tlustoš, V., Analytical and


Abstract

Lead isotopic studies in soils provide an efficient tool for tracing the

sources of lead pollution. Five different extraction/digestion techniques

(0.05 mol/L EDTA, 0.5 mol/L HNO3, 2 mol/L HNO3, aqua regia, total

digestion) were used for lead isotopic composition (206Pb/207Pb)

determination in three forest soil profiles with different kinds of prevailing

Pb contamination (unpolluted area, smelting area and vicinity of a

motorway). The results obtained showed that all extraction/digestion

methods used for the determination of 206Pb/207Pb ratios in surface horizons

containing high organic matter contents gave statistically identical values

(according to the Tukey test). In mineral soil horizons, differences between

the individual extraction/digestion methods could be observed (the lowest 206Pb/207Pb ratios were obtained from EDTA extracts, corresponding to

weakly bound anthropogenic lead, and the highest 206Pb/207Pb ratios were

obtained from total digestion). The combination of total digestion and

EDTA extraction (labile lead fraction) seems to be the optimal combination

for 206Pb/207Pb ratio determination and optimal result interpretation.

Type of sample: Soils

Sample amount: 0.5 and 1.0 g



Heating: All digestion procedures were optimized for microwave digestion

according to the US EPA 3051A method.


Reagents: 10 mL of 0.5 mol/L HNO3 (1 g soil sample); 10 mL of 2 mol/L

HNO3 (1 g soil sample); 3 mL HNO3 + 9 mL HCL (0.5 g soil sample); and,

3 mL of HNO3, + 3 mL of HClO4 + 3 mL of HCl + 3 mL of HF (0.5 g soil

sample).

Pretreatment general aspects: Soil and bedrock samples used for total

digestion were finely ground in an agate mortar.


Analytes: Pb

Improved elemental recoveries in soils with heating boric acid

following microwave total digestion

Wilson, M. A., Burt, R. and Lee, C. W., Communications in Soil Science

and Plant Analysis, 37 (3-4), 513-524, 2006

Abstract

Microwave digestion of soils for elemental analysis commonly uses

hydrofluoric acid (HF) because of insolubility of aluminosilicate minerals

in other acids. Boric acid is added following digestion to complex F in

solution. Low recoveries of calcium (Ca), aluminum (Al), and magnesium

(Mg) of soil reference materials led to this investigation of a secondary

heating of the boric acid with digested soil. The objectives were to evaluate

boric acid (H3BO3) concentrations needed to complex F from 4 mL HF and

to evaluate soil characteristics that may contribute to the formation of

metal-fluoride complexes that decrease recovery following digestion. Four

standard soil reference materials and a variety of soil samples (n = 75) were

evaluated. Heating 20 mL 2.5% H3BO3 with a digested standard reference

soil produced recoveries of 94, 98, and 99% for Al, Ca, and Mg,

respectively, compared to 46% for Al and Mg and 37% recovery for Ca in

extracts where H3BO3 was added but not heated. Two other concentrations

of H3BO3 were tested with slightly improved recoveries, and results

suggest that 20 mL of a 4.5% H3BO3 solution was sufficient to maximize

recoveries. Digestion of soil samples by both the nonheated and heated

H3BO3 methods showed that recovery difference between the two methods

ranged from 0 to 100% for Al and Ca. Assuming that this difference in

recovery was related to the formation of metal fluorides, correlation with

clay and C in soils may reflect the positive or negative influence of these

constituents on the formation of these complexes, respectively.


Sample amount: 0.250 g for all methods


USA)


Heating: 180 ºC for 9.5 min for “original method” (based on EPA 3052);

160 ºC for 10 min for methods 1 and 2.


Reagents: 9 mL of concentrated HNO3, 4 mL of concentrated HF, 3 mL of

concentrated HCl and 2.5% (w/v) of H3BO3 for original method; 20 mL of

2.5% (w/v) of H3BO3 for method 1; 50 mL of 2.5% (w/v) of H3BO3 for

method 2.



Analytes: Al, Ca, and Mg

Novel matrix separation—on-line pre-concentration procedure for

accurate quantification of palladium in environmental samples by

isotope dilution inductively coupled plasma sector field mass

spectrometry

Rudolph, E., Limbeck, A. and Hann, S., Journal of Analytical Atomic

Spectrometry, 21 (11), 1287-1293, 2006

Abstract

A method for accurate on-line ultra-trace analysis of palladium by

inductively coupled plasma mass spectrometry has been developed. After

separation of interfering cations by cation exchange chromatography,

palladium was selectively adsorbed on to a C18 micro-column on-line

which had been reversibly loaded with the complexing agent N,N-diethyl-

N’-benzoylthiourea (DEBT). The palladium complex formed was eluted

with methanol and introduced into an ICP-SFMS via microconcentric

nebulization with membrane desolvation. Quantification of palladium was

carried out by isotope dilution analysis. The results obtained via the isotope

ratios of 105Pd/108Pd and 106Pd/108Pd agreed within their measurement

uncertainty. For solid samples (total intake 100 mg, final sample volume of

10 mL after closed vessel microwave digestion) the limit of detection was

0.24 ng/g palladium (2 mL of digested sample). The necessity of

combining matrix separation and pre-concentration for elimination of

spectral interferences was demonstrated using soil samples. The method

was validated by analysis of the certified reference material BCR-723 (road

dust).



Microwave oven (model): MLS 1200 mega (Microwave Laboratory

Systems)


Heating: The first microwave program was as follows: (step 1) 1 min,

250 W at 220 °C; (step 2) 1 min, 0 W at 220 °C; (step 3) 5 min, 250 W at

220 °C; (step 4) 5 min, 400 W at 220 °C; (step 5) 5 min, 600 W at 220 °C.

A second digestion procedure was performed: (step 1) 1 min, 250 W at

220 °C; (step 2) 2 min, 0 W at 220 °C; (step 3) 1 h, 400 W at 220 °C.


Reagents: 4 mL HNO3 conc.+ 1 mL H2O2 conc.



Analytes: Pd

Single-step microwave digestion with HNO3 alone for determination of

trace elements in coal by ICP spectrometry

Wang, J., Nakazato, T., Sakanishi, K., Yamada, O., Tao, H. and Saito, I.,

Talanta, 68 (5), 1584-1590, 2006

Abstract

A microwave digestion method with HNO3 alone was conducted at a

temperature as high as 250 °C for determination of 19 trace elements (Li,

Be, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Cd, Cs, Ba, Hg, and Pb)

in coal jointly by inductively coupled plasma optical emission spectrometry

(ICP-OES), inductively coupled plasma mass spectrometry (ICP-MS), and

flow injection ICP-MS (FI-ICP-MS). The validity of determination was

assessed by using three standard coals, SRM 1632c, BCR 180, and SARM

19. It was found that the high-temperature digestion led to an extensive

decomposition of the organic matrix and clay in coal, and no dissolved and

solid carbon remained in the final solution after evaporation. Good

recoveries were observed for all trace elements in three coals, with the

exception of V, Rb, and Cs in high-ash SARM 19. Additionally, FI-ICP-

MS combined with the present digestion without evaporation pretreatment

was proved to be a rapid and efficient approach for determination of ultra-

trace elements such as Se, Cd, and Hg in coal.

Type of sample: coal




Heating: the temperature rose from room temperature to 200 °C in the first

30 min, and then to about 250 °C in the later 30 min with the pressure of

about 7.5 MPa


Reagents: 3 mL of concentrated HNO3


Detection technique: ICP-OES, ICP-MS and FI-ICP-MS

Analytes: Li, Be, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Cd, Cs,

Ba, Hg, and Pb

The form, distribution and mobility of arsenic in soils contaminated by

arsenic trioxide, at sites in southeast USA

Yang, L. and Donahoe, R. J., Applied Geochemistry, 22 (2), 320-341, 2007

Abstract

Soils from many industrial sites in southeastern USA are contaminated

with As because of the application of herbicide containing As203. Among

those contaminated sites, two industrial sites, FW and BH, which are

currently active and of most serious environmental concerns, were selected

to characterize the occurrence of As in the contaminated soils and to

evaluate its environmental leachability. The soils are both sandy loams with

varying mineralogical and organic matter contents. Microwave-assisted

acid digestion (EPA method 3051) of the contaminated soils indicated As

levels of up to 325 mg/kg and 900 mg/kg (dry weight basis) for FW and

BH soils, respectively. However, bulk X-ray powder diffraction (XRD)

analysis failed to find any detectable As-bearing phases in either of the

studied soil samples. Most of the soil As was observed by scanning

electron microscopy, coupled with energy dispersive X-ray spectroscopy

(SEM/EDX), to be disseminated on the surfaces of fine-grained soil

particles in close association with Al and Fe. A few As-bearing particles

were detected in BH soil using electron microprobe analysis (EMPA).

Synchrotron microXRD and X-ray absorption near-edge structure

(XANES) analyses indicated that these As-rich particles were possibly

phaunouxite, a mineral similar to calcium arsenate, which could have been

formed by natural weathering after the application of As2O3. However, the

scarcity of those particles eliminated them from playing any important role

in As sequestration.

Synthetic acid rain sequential batch leaching experiments showed

distinct As leaching behaviors of the two studied soil samples: BH soil,

which has the higher As content, showed a slow, steady release of As,

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while FW soil, with a lower As content, showed a much quicker release

and lower overall retention of As upon leaching. Sequential chemical

extraction experiments were carried out using a simplified 4-step sequential

chemical extraction procedure (SCEP) previously developed to characterize

the fractionation of As and better understand the different leaching

behaviors of the two studied soils. It was shown that only about 50% of the

total extractable As was removed by the first two extraction steps, which

represented the most weakly bonded and readily available As for

environmental leaching. Compared with the sequential leaching

experiments, it was further indicated that only half of the As associated

with phases extracted by the second SCEP step was mobilized by SPLP

leaching. Although microwave-assisted acid digestion results showed

similar Al and Fe contents in both soils, the sequential chemical extraction

experiments indicated that BH soil has a much higher content of

amorphous Al and Fe phases and that a comparably higher portion of soil

As was associated with those materials. The experimental results suggest

that remediation efforts for the contaminated sites can be directed towards

enhancing the formation of more stable As-bearing compounds in the soils

to reduce the environmental leachability of As.



Microwave oven (model): MLS-1200 MEGA (Milestone, Sorisole, Italy)


Heating: US EPA Method 3051


Reagents: 10 mL concentrated HNO3


Detection technique: ICP OES, Perkin–Elmer Optima 3500DV model

Analytes: As

Comparison of three optimized digestion methods for rapid

determination of chemical oxygen demand: Closed microwaves, open

microwaves and ultrasound irradiation

Domini, C. E., Hidalgo, M., Marken, F. and Canals, A., Analytica Chimica

Acta, 561 (1-2), 210-217, 2006

Abstract

In the present work, experimental design was used for the fast optimization

of three kinds of sample digestion procedures with the final aim of

obtaining the COD value of wastewater samples. The digestion methods

evaluated were “closed microwave-assisted” (CMWD), “open microwave-

assisted” (OMWD) and “ultrasound-assisted” (USD). Classical digestion

was used as reference method. The optimum values for the different

variables studied in each method were: 0.006 atm pressure, 475 W power

and 4 min irradiation time (CMWD); 150 °C temperature and 4 min

irradiation time (OMWD); 90% of maximum nominal power (180 W), 0.9

s (s−1) cycles and 1min irradiation time (USD). In all cases, interference

concentration that produces a deviation of 10% in COD values is 13.4,

23.4, 21.1 and 2819 mg/L for S2-, Fe2+, NO2- and Cl-, respectively. Under

optimum conditions, the proposed digestion methods have been

successfully applied, with the exception of pyridine, to several pure organic

compounds and COD recoveries for 10 real wastewater samples were

ranged between 88 and 104% of the values obtained with the classical

(open reflux) method used as reference, with R.S.D. lower than 4% in most

cases. Thus, the use of ultrasound energy for COD determination seems to

be an interesting and promising alternative to conventional open reflux and

microwave-assisted digestion methods used for the same purpose since the

instrumentation is simpler, cheaper and safer and the digestion step faster

than the ones used for the same purpose.

Type of sample: wastewater

Sample amount: 9 mL

Microwave oven (model): Star System 2 TM, CEM Corporation,

Matthews NC, USA and a closed microwave MSP 1000, CEM

Corporation, Matthews NC, USA.

Vessel material: glass

Heating: Three parameters (pressure, power and irradiation time) were

programmed according to the experimental design. Closed system:

maximum recovery was found for the values of pressure, power and

irradiation time fixed at 6.12 atm, 475 W and 4 min, respectively. Open

system: maximum recovery for COD was found when the values of

temperature and irradiation time were fixed at 150 °C and 4 min,

respectively.


Reagents: 18 mL of digestion solution: 0.0417 mol/L in K2Cr2O7,

3.0 mol/L in H2SO4, and 0.11 mol/L in HgSO4. Previously, silver sulphate

was added to the sulphuric acid in the proportion 5.5 g of Ag2SO4 per kg of

H2SO4.


Detection technique: titration

Analytes: COD (chemical oxygen demand)

Exploiting in situ hydride trapping in tungsten coil atomizer for Se and

As determination in biological and water samples

Souza, S. S., Santos Jr., D., Krug, F. J. and Barbosa Jr., F., Talanta, 73 (3),

451-457, 2007

Abstract

A flow injection hydride manifold was coupled to a 150 W tungsten coil

electrothermal atomizer for in situ hydride collection followed by selenium

and arsenic determination by ET AAS. Rhodium (200 μg), thermally

reduced over the double layer tungsten atomizer, was very efficient at

collecting selenium or arsenic hydrides. Prior to analysis, biological

samples were digested in closed-vessels microwave digestion system. Prior

to the hydride formation, both selenium and arsenic were reduced to

valence state (IV) and (III), respectively. The detection limit was 35 ng/L

for selenium and 110 ng/L for arsenic. Sample throughput was 70 h−1 using

30 s of hydride trapping time. Method accuracy was evaluated by analyzing

biological-certified reference materials from the National Institute of

Standard and Technology (SRM-1577a and SRM-1577b “bovine liver” and

RM-8414 “bovine muscle powder”) and from the International Agency for

Energy Atomic (A-13 “animal blood”) and one water-certified reference

material from the National Institute of Standard and Technology (SRM-

1640 trace elements in natural water). By applying a t-test, there was no

significant difference at the 95% probability level between the results

obtained with the proposed method and those certified values.

Type of sample: water


Microwave oven (model): ETHOS 1600 Milestone, Sorisole, Italy


Heating: Step 1: 160 oC, 550 W, 3 min. Step 2: 160 oC, 0 W, 3 min. Step 3:

180 oC, 700 W, 5 min. Step 4: 230 oC, 1000 W, 15 min




Detection technique: WCAAS

Analytes: Se and As

Lead ultra-trace on-line preconcentration and determination using

selective solid phase extraction and electrothermal atomic absorption

spectrometry: applications in seawaters and biological samples

Alonso, E. V., Cordero, M. T. S., Torres, A. G. and Pavón, J. M. C.,

Analytical and Bioanalytical Chemistry, 385 (7), 1178-1185, 2006

Abstract

In this work, a new chelating resin [1,5-bis(2-pyridyl)-3-sulphophenyl

methylene] thiocarbonohydrazide immobilised on aminopropyl-controlled

pore glass (550 Å; PSTH-cpg) was synthesised and packed in a

microcolumn which replaced the sample tip of the autosampler arm. The

system was applied to the preconcentration of lead. When microliters of

10% HNO3, which acts as elution agent, pass through the microcolumn, the

preconcentrated Pb(II) is eluted and directly deposited in a tungsten-

rhodium coated graphite tube. With the use of the separation and

preconcentration step and the permanent modifiers, the analytical

characteristics of the technique were improved. The proposed method has a

linear calibration range from 0.012 to 10 ng/mL of lead. At a sample

frequency of 36 h−1 with a 90 s preconcentration time, the enrichment

factor was 20.5, the detection and determination limits were 0.012 and

0.14 ng/mL , respectively and the precision, expressed as relative standard

deviation, was 3.2% (at 1 ng/mL). Results from the determination of Pb in

biological certified reference materials were in agreement with the certified

values. Seawaters and other biological samples were analysed too.

Type of sample: Water and biological samples




Heating: microwave oven to a power of 5% for 5 min. After this, 1 mL

35% H2O2 was added and the sample was subjected again to 5% of power

for 5 min.


Reagents: 1.5 mL H2SO4 conc. + 2.0 mL HNO3 conc. + 1.0 mL H2O2

35% (m/v)

Pretreatment general aspects: The samples were dried


Analytes: Pb

Microwave-assisted UV-digestion procedure for the accurate

determination of Pd in natural waters

Limbeck, A., Analytica Chimica Acta, 575 (1), 114-119, 2006

Abstract

A procedure was developed for the selective determination of Pd in

environmental aquatic solutions. The method is based on a preliminary

microwave-assisted UV-digestion for the degradation of dissolved organic

material, and the subsequent determination of Pd using a recently presented

enrichment procedure with ET AAS detection. Due to the simultaneous use

of microwave and UV irradiation only extremely small quantities of

hydrogen peroxide were necessary to yield a quantitative degradation of

interfering organic ligands. Thus the on-line pre-concentration of Pd in the

digested samples using the complexing agent N,N-diethyl-N’-

benzoylthiourea was possible without any further sample pre-treatment.

Using a sample volume of 1.57 mL for FI-ET AAS analysis a limit of

detection of 15 ng/L was obtained for the combined procedure, with a

relative standard deviation being not more than 4.9%. The method was

applied to quantify the water-soluble fraction of Pd in urban road dust.

Extractions with a rain sample of pH 5.9 revealed that an average of 2.2%

(n = 8) of the total Pd present in urban road dust was water soluble.

Type of sample: natural waters

Sample amount: 10 mL or 0.1 g

Microwave oven (model): Multiwave 3000, Anton Paar, Austria

Vessel material: quartz and PTFE

Heating: 5 min ramp, followed by a 15 min hold time at the maximum

power of 1000 W (maximum temperature and pressure 240 °C and

39.4 atm, respectively).


Reagents: 3 mL HCl + 2 mL HNO3 + 0.5 mL HF + 10 µL H2O2



Analytes: Pd

Preface - UFSCardq-gaia/images_2007/cookbook.pdf · Preface This manual contains procedures...

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