D1.3.16 M37 (by 1/2/08) - Report on evaluation of ......Principle Edible parts are grinder and...

1

Project no.FP6 - 513944

EuroFIR

EUROPEAN FOOD INFORMATION RESOURCE NETWORK

Instrument: Network of Excellence

Thematic Priority: 5 – Food Quality and Safety

D1.3.16 – M37 (by 1/2/08) - Report on evaluation of analytical methods

according with compilers needs 4/5 (Minerals and Trace Elements)

Due date of milestone or deliverable: 1/2/08

Actual submission date: 18/03/08*(available at Technical webside)

Start Date: January 01, 2005 Duration: 5 years

Organisation name of lead contractor for this deliverable or milestone –

INSA – Partner 24

Project co-funded by the European Commission within the Sixth Framework Programme

(2002-2006) Dissemination Level (please check appropriate box)

PU Public

PP Restricted to other programme participants (including the Commission Services)

RE Restricted to a group specified by the consortium (including the Commission Services)

CO Confidential, only for members of the consortium (including the Commission Services) x

EuroFIR guidelines for assessment of Methods of Analysis

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Methods of analysis

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Index

Minerals and Trace Elements ........................................................................................... 3

(i) Copper .............................................................................................. 10

(i) Iron ................................................................................................... 23

(i) Magnesium ....................................................................................... 30

(ii) .......................................................................................................... 30

(i) Phosphorus ....................................................................................... 36

(i) Potassium .......................................................................................... 42

(i) Selenium ........................................................................................... 48

(i) Sodium .............................................................................................. 58

(i) Zinc ................................................................................................... 65

(i)


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Methods of analysis

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Minerals and Trace Elements


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Methods of analysis

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Calcium

Calcium (Ca) belongs to group II of the third period of the Periodic Table of Elements. It has an

atomic weight of 40.08; its atomic number is 20, its valency is 2. It is the fifth most abundant element

in the human body (EFSA, 2003)

Golden Standard

ISO 11885: 2007 Water quality -- Determination of selected elements by inductively coupled

plasma optical emission spectrometry (ICP-OES)

ISO 17294:2003: Water quality -- Application of inductively coupled plasma mass spectrometry

(ICP-MS) -- Part 2: Determination of 62 elements

prEN 15505 Foodstuffs - Determination of trace elements - Determination of sodium,

magnesium by flame atomic absorption spectrometry (AAS) after microwave digestion

AOAC 984.27 – ICP-OES Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus,

Potassium, Sodium, and Zinc in Infant Formula

NMKL no 147 (2003). Magnesium and calcium; determination in foodstuffs using flame atomic

absorption spectrometry after microwave oven digestion.

Scope

Determination of Calcium in foodstuffs in all relevant matrix successfully tested in laboratory

proficiency testing.

Principle

Edible parts are grinder and homogenised in suitable apparatus. The organic matrix are

removed by microwave digestion. The Calcium content is determined by flame atomic

absorption spectrometry-procedures( AAS) or by Inductively coupled plasma atomic emission


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Methods of analysis

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spectroscopy (ICP-AES) also refered as Inductively Coupled Plasma Optical Emission

Spectrometry (ICP-OES).

Key steps

Secção 1.02

Preparation

o The edible part needs to be separate from the foodstuffs ( EN 13804:2002

provide examples of sample preparation from foodstuffs)

Homogenization

o Edible parts are grinder in suitable apparatus (coffee grinder or kitchen

grinder; stainless steel vegetable slice; plastic salad spinner and homogenised;

o To avoid contamination the apparatus equipped with titanium or ceramics

knives, agate mortar or ball mill can be used for size reduction and

homogenisation( EN 13804:2002 is the reference standard for sample

preparation

Separation

Organic matrix are removed or extracted :

o Pressure digestion: The sample dissolved in concentrated acid are digested

in a sealed vessel in a pressure container at high temperature and pressure by

conventional or microwave assisted heating. The method is described for AAS

and ICP OES.

Detection

o The instrumental parameters for flame AAS

Flame: Air acetylene, oxidising

Wavelength 422.7nm

o The instrumental parameters for ICP-OES

Wavelength 315,887 nm; Interferences: Co, Mo Limit of Quantification:

(radial viewing 100 ; axial viewing 13)


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Methods of analysis

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Wavelength 317,933 nm ; Fe, V interferences; Limit of Quantification:


Wavelength422,673 nm ; Mo,V, Zr interferences; Limit of Quantification:


Quantification

o AAS

After instrument response is stable the linearity, sensitivity and limit of

quantification verified. The content of Calcium in sample is determined

from calibration curve by plotting (absorbance (A) peak area ) against

concentration. The calibration curve is prepared with at least five

points using concentrations of standard solutions within working range.

o ICP OES

After verification of instrument performance (drift; interferences,

background correction). The content of Calcium in sample is

determined from linear regression method using blank, standard

solutions and , internal standards

Criteria for analytical performance and Analytical Quality

control

Method Performance

Table 1. Relevant parameters obtained by EN 15505 inter laboratory studies

Matrix

Parameter

Wheat

Bran

Simulated

diet

Simulated

diet

Milk

powder

Minced

fish

Apple Chocolate

RSD r % 5.5 4.7 4.3 3.6 2.4 7.8 7.3

RSD R% 19 23 15 6.3 5.9 22 20


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Methods of analysis

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Certified Reference Materials/Standard Reference Material

Table 2. List of Available CRM/SRM in 2008

LGC 7104 Sterilized cream

NIST 2384 Baking chocolate(reference value)

LGC 7112 Pig liver Paste

NIST 2387 Peanut Butter

GBW 08552 Freeze dried Pork Muscle

LGC 7000 Beef Pork Meat

NIST 1546 Meat Homogenate(reference

value)

NIST 8415 Whole Egg Powder(reference

value)

BCR 381 Rye Flour

BCR 383 Freeze Dried Green Beans

GBW 07605 Tea

NIST 1567a wheat Flour

NIST 1568a Rice Flour

NIST 2383 Baby Food(reference value)

NIST 8432 Corn Starch (reference value)

NIST 8433 Corn Barn(reference value)

NIST 8436 Durum Wheat Flour(reference

value)

VMA 195 Cereal

VMA 399 Cereal

LGC 7105 Rice Pudding

NIST 1548a Freeze Dried Mixed Diet

NIST 1846 Infant Formula(reference value)

NIST 8435 Whole Milk Powder(reference

value)

LGC 7001 Pork Meat

NIST 1549 Non- Fat Milk Powder

NIST 1566b Freeze Dried Oyster Tissue


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Methods of analysis

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NIST 1570a Freeze Dried Spinach Leaves

NIST 2385 Slurried Spinach

NIST 1946 Fish Tissue(reference value)

LGC 7160 Crabe Paste

NIST 1577b Freeze Dried Bovine liver

NIST 3244 Protein Powder

NIST 8418 wheat gluten (reference value)

Proficiency Testing Schemes (www.eptis.bam.de)

o 26 Providers are register in the database

o Following matrix are registed

Wine, water, animal feeds, diet food, baby food, fruit juice, carbonate

soft drinks, syrup, meat products, plants, milk powder, UHT milk,

cheese processed, sausage boiled, dietary supplements

Other methods available

Table 3. CodexStan 234-1999)- Recommended methods of analysis

Matrix

Method Reference Principle Type

Canned green peas AOAC 968.31 Complexomteric titrimetry II

Canned strawberries AOAC 968.31 Complexometric titrimetry II

Canned tomatoes AOAC 968.31 Complexometric titrimetry II

Citrus marmalade AOAC 968.31 Complexometric titrimetry II

Jams (fruit preserves)

and jellies

AOAC 968.31 Complexometric titrimetry II

Natural mineral waters ISO 6058:1984 Titrimetry II

Natural mineral waters ISO 7980:1986(confirmed

1995)

Atomic absorption

spectrophotometry

III

Special foods AOAC 984.27 ICP emission spectrometry III

Food grade salt ISO 2482:1973 Complexometric titrimetry II

http://www.eptis.bam.de/


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Methods of analysis

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Compatibility of old data

o All methods give similar results depends on amount of mineral present

(methods have different limits of quantification).

References

Deharveng G., Charrondière UR, Slimani N., Southgate DAT., Riboli E. (1999)

Comparison of nutrients in food composition tables available in the nine European

countries participating in EPIC. European Journal of Clinical Nutrition 53, 60-79

Greenfield H, Southgate DAT (2002). Food Composition Data – Production,

Management and Use. Elsevier Applied Science, London, UK

Pohl, P., & Prusisz, B. (2007). Determination of Ca, Mg, Fe and Zn partitioning in UHT

cow milks by two-column ion exchange and flame atomic absorption spectrometry

detection. Talanta, 71(2), 715–721.

Kaare J., Amund M., Wallin, Harriet C (1998).Determination of Magnesium and Calcium

in Foods by Atomic Absorption Spectrometry after Microwave Digestion: NMKL

Collaborative Study. Journal of AOAC international 81 (6) 1202-1208.

EuroFIR assistance to this method/guidelines


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Methods of analysis

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(i) Copper

Copper is a transition metal with an atomic mass of 63.54. Three oxidation states of copper exist;

cuprous (Cu+), cupric (Cu2+) and Cu0 (Uauy et al, 1998). In biological systems, copper primarily exists

as Cu2+ with minute quantities of Cu+ being found in solution. (EFSA, 2003)

Golden Standard





EN 14084:2003 Foodstuffs - Determination of trace elements - Determination of lead,

cadmium, zinc, copper and iron by atomic absorption spectrometry (AAS) after microwave

digestion


cadmium, zinc, copper, iron and chromium by atomic absorption spectrometry (AAS) after dry

ashing

i. Method Indicator

Name

Code

Scope

Determination of Copper in foodstuffs in all relevant matrix successfully tested in laboratory


Principle


removed by microwave digestion or by dry ashing. The Copper content is determined by


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Methods of analysis

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flame atomic absorption spectrometry-procedures( AAS) or by Inductively coupled plasma

atomic emission spectroscopy (ICP-AES) also refered as Inductively Coupled Plasma Optical

Emission Spectrometry (ICP-OES).

Key steps

Secção 1.03

Preparation



Homogenization






preparation

Separation




conventional or microwave assisted heating. (EN 14084:2003 Foodstuffs). The

method is described for AAS and ICP OES.

o Dry Ashing : Sample in a crucible made by platinum is incinerated heating

gentling in a muffle furnace at controlled temperature 450 ºC 25 ºC. Final

residue redissolved in nitric acid .( EN 14082:2003). The method is described

for AAS.


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Methods of analysis

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Detection



Wavelength 324,7 nm


Wavelength 324,754 nm; Interferences:Cr, Fe, Mo, Ti Limit of Quantification:

(radial viewing 9 ; axial viewing 2 )

Wavelength 327,396 nm ; Co and Ti interferences; Limit of Quantification:


Quantification

o AAS


quantification verified. The content of Copper in sample is determined




o ICP OES


background correction). The content of Copper in sample is




control

Method Performance


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Methods of analysis

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Table 4. Relevant parameters obtained during inter laboratory studies during preparation of Golden Standards

Matrix

Standard/Matrix

Liver

paste

Apple

sauce

Minced

fish

Wheat

bran

Milk

powder

Composite

diet D/E

EN

14082

Repeatability

RSDr%

1,8

Reproducibility

RSDR (%)

4,2 *

6,0* 12* 6,9* 8,0* 3,5*

AOAC

999.11

Repeatability

RSDr%

5.3 1.8

Reproducibility

RSDR (%)

7.5 6.8 6.8 8.0 3.5

Liver Mushroom Fish Wheat

bran

Milk

powder

Diets

AOAC

999.10

Repeatability

RSDr%

1.6 - - 3.4 4.0

Reproducibility

RSDR (%)

4.8 5.3 9.1 4.8 9.3 5.3

EN

14084

Repeatability

RSDr%

3.1

7,2

1,5

Reproducibility

RSDR (%)

3,8

5,7

28

10

27

3,0


Table 5. List of CRM/SRM available in 2008

NIST 2381 Baking Chocolate (reference value)

LGC 7112 Pig liver paste

NIST 2387 Peanut butter

GBW 08552 Freeze Dried Pork Muscle

NIST 1546 Meat Homogenate


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Methods of analysis

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NIST 8415 Whole Egg Powder(reference value)

BCR 189 Wholemeal flour

BCR 679 Freeze dried Whole Cabbage

GBW07605 Tea

NIST 1567a Wheat Flour

NIST 1568 a Rice Flour

NIST 2383 Baby Food (reference value)


NIST 8433 Com Bran (reference value)

NIST 8436 Durum Wheat Flour (reference value

VMA195

Cereal

NIST 1548a

Freeze Dried Mixed Diet

NIST 8435 Whole Milk Powder (reference value)

NIST 1846 Infant Formula (reference value)

ERMCE 278 Freeze Dried Muscle Tissue

NRCDORM2 Freeze Dried Dogfish Muscle

NIST 1549 Non –Fat Milk Powder

NIST 1566b Freeze-Dried Oyster Tissue

NIST 1570b Freeze dried Spinach Leaves

NIST 1946 Fish Tissue (reference value)


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Methods of analysis

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BCR 422

Freeze – dried cod muscle

LGC 7160 Crab Paste

NIST 1577b Freeze –Dried Bovine liver


NRCDOLT3 Freeze Dried Dogfish liver


o 21 datasets are register at eptis and the following matrix

Wine, Sewage sludge, vegetable oil, fat vegetable, fish oil (GFAAS),

diet food, babby food, fat animal, frying oil, Groundnut oil, Colza oil,

wheat, milk powder, flour, Mushrooms, plants, tuna fish,


Colorimetric

AOAC 984.27- Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus,

Potassium, Sodium, and Zinc in Infant Formula- Inductively Coupled Plasma Emission

Spectroscopic Method

NMKL- AOAC 999.10 -Lead, Cadmium, Zinc, Copper, and Iron in Foods – Atomic

Absorption Spectrophotometry after microwave digestion

NMKL-AOAC 999.11- Lead, Cadmium, Zinc, Copper, and Iron in Foods – Atomic

Absorption Spectrophotometry after dry ashing



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Methods of analysis

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Table 6. Recommended methods of analysis CodexStan 234-1999)-

Matrix


Chocolate AOAC 960.40 (Codex general

method)

Colorimetry

(diethyldithiocarbamate)

II

Cocoa (cacao) nib,

cocoa (cacao)

mass, cocoa press

cake and cocoa dust

(cocoa fines), for use

in the

manufacturing of

cocoa and chocolate

products

AOAC 971.20 (Codex general

method)

Atomic absorption

spectrophotometry

II

Cocoa butter

confectionery


method)

Atomic absorption

spectrophotometry

II

Cocoa butters AOAC 990.05

ISO 8294:1994

IUPAC 2.631

(Codex general method)

Atomic absorption

spectrophotometry

(direct graphite furnace)

II

Cocoa butters AOAC 960.40 (Codex general

method)

Colorimetry


III

Cocoa powders

(cocoa) and dry

cocoasugar

mixtures


method)

Colorimetry


II

Edible casein products AOAC 985.35 Atomic absorption

spectrophotometry

II

Edible casein products IDF Standard 76A:1980

ISO 5738:1980 (confirmed

1995)


method)

Colorimetry

(diethyldiethiocarbamate)

III


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Methods of analysis

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Fats and oils AOAC 990.05

ISO 8294:1994

IUPAC 2.631


Atomic absorption

Spectrophotometry (direct

graphite

furnace

II

Copper Food grade

salt

ESPA/CN-E/101-1994 Photometry II

Fruit juices AOAC 971.20(Codex general

method)

Atomic absorption

spectrophotometry

II

Honey AOAC 971.20 (Codex general

method)

Atomic absorption

spectrophotometry

II

Natural mineral waters ISO 8288:1986 (confirmed

1995)

Flame atomic absorption

spectrophotometry

II

Natural mineral waters AOAC 960.40 (Codex general

method)

Colorimetry III

Vinegar AOAC 971.20(Codex general

method)

Atomic absorption

spectrophotometry

II

Whey powders AOAC 985.35 Atomic absorption

spectrophotometry

II

Whey powders IDF Standard 76A:1980


1995)


method)

Photometry

(diethyldiethiocarbamate)

III

Remarks

Compatibility of data

o All methods give comparable results

o In certification campaign for BCR 063r the following methods were used for

final determination

Direct current plasma atomic emission spectrometry

Differential pulse anodic stripping voltammetry

Electrothermal atomic absorption spectrometry


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Methods of analysis

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Inductively coupled plasma atomic emission spectrometry (ICP-OES)

Inductively coupled plasma mass- spectrometry (ICP-MS)

Isotope dilution mass spectrometry

Neutron activation analysis

Spectrophotometry

References




Cubbada, F., (2004). Inductively Coupled Plasma-Mass Spectrometry for the

determination of Elements and Elemental Species in Food: a review.J. AOAC

International, 87: 173-204

www.irmm.jrc.be/reference_materials_catalogue/BCR-063r

Greenfield H, Southgate DAT (2002) Food Composition Data – Production,


Jorhem, L. (2000). Determination of Metals in Foods by Atomic Absorption

Spectrometry after Dry Ashing: NMKL Collaborative Study. Journal of AOAC

INTERNATIONAL , 83 (5), 1204-1211


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Methods of analysis

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Iodine

Iodine is a reactive Periodic Group VII element (halogen) existing in the valency states -1 to +7

but not occurring free in nature

Golden Standard

EN 15111:2007 Foodstuffs - Determination of trace elements - Determination of iodine by ICP-

MS (inductively coupled plasma mass spectrometry)

(i) Method Indicator

Name

Code

Scope

Extraction method for the determination of iodine compounds in foodstuffs by inductively

coupled plasma mass spectrometry (ICP-MS).

Principle

Iodine compounds are extracted with a strong alkaline reagent at elevated temperature. After

removing un-dissolved components, the nebulized solution is atomized and ionized in an

inductively coupled argon plasma. The ions are extracted from the plasma by a system of

sampler and skimmer cones, separated in a mass spectrometer on the basis of their

mass/charge ratio and determined using a pulse counting detector system

Key steps

Extraction

o Iodine compounds are extracted using tetramethylammonium hydroxide in

a dry oven at (90 ± 3) ºC

Separation for matrix

o Filtration or centrifugation


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Methods of analysis

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Identification

L

o Iodine shall be evaluated at a mass of 127. The masses 125, 126 or 128 can be

used to evaluate the internal standard tellurium.

Quantification

o Determine the sample content against a calibration curve prepared with iodine

calibration solutions. The slope of calibration graph should be checked after

regular intervals (ex: 10 samples)


control

Method Performance

Table 7. Relevant parameters of inter laboratory studies during preparation of ISO standard

Matrix

Parameter

Pig

Kidney

Ready-to-

serve

milk

pudding

Soy

product

Cod

Muscle

Iodised

Salt

Marine

Algae

Limit of

Quantification

(LOQ)

0,5 µg/l

RSDr (%) 7.6 7,8 3.7 0.7 6.4 0.9

RSDR (%) 19 13 6.7 8.9 15 6.2


o BCR 63R SKIM Milk powder (ICP _MS)

o BCR 150 spiked skim milk powder

o BCR 151 Spiked skim milk powder





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Methods of analysis

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Diet Food ; Premix; Iodized salt


Catalytic measurements

Gas Chromatography

Isotope dilution mas spectrometry

Voltammetric techniques

X-Ray Fluorescence spectrometry

Dry ashing followed by titration

AOAC 992.22 Iodine (as Iodide) in Pasteurized Liquid Milk and skim milk powder (

GLChomatography)

Table 8. Recommended methods of analysis CodexStan 234-1999

Matrix


Food grade salt ESPA/CN-E/109-1994 Titrimetry using sodium

thiosulphate

II

Food grade salt AOAC 925.56 Titrimetry using sodium

thiosulphate

III

Foods with low-

sodium content

(including salt

substitutes)

AOAC 925.56 Titrimetry II

(milk based formula)

Infant formula and

follow-up formula

AOAC 992.24 Ion-selective potentiometry II

Remarks

ICP-MS :This procedure requires an adequate amount of experience in operating and

optimizing the apparatus.

This limit of determination is strongly influenced by the purity of TMAH (tetramethylammonium

hydroxide) and the stability of the blank signal during measurement


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Methods of analysis

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o Interlaboratories studies using spectrometric determination after digestion [2], ICP-

MS analysis after combustion in oxygen [3], or after digestion with nitric acid /

perchloricacid) performed in parallel by three laboratories revealed no significant

difference from the extraction method using dry oven at 90 ºC followed ICP-MS

determination

o In certification exercise for BCR 151 a large range of preatment techniques are

used and the following methods for final determination:

o Catalytic measurements

o Gas Chromatography

o Isotope dilution mas spectrometry

o Voltammetric techniques

o X-Ray Fluorescence spectrometry

o

References




Cubbada, F., 2004. Inductively Coupled Plasma-Mass Spectrometry for the





www.irmm.jrc.be/reference materials_Catalogue_BCR-151



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Methods of analysis

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(ii) Iron

Iron is a metal with an atomic mass of 55.8. It is present in biological systems in one of two oxidation

states, and redox interconversions of the ferrous (Fe2+) and ferric (Fe3+) forms are central to the

biological properties of this mineral. Iron is an essential constituent of oxygen carriers, such as

haemoglobin and myoglobin, and the iron contained within haem is essential for the redox reactions

of numerous cytochromes.(EFSA, 2003)

Golden Standard







digestion



ashing

(iii) Method Indicator

Name

Scope

Scope

Determination of Iron in foodstuffs in all relevant matrix successfully tested in laboratory



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Methods of analysis

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Principle


removed by microwave digestion or by dry ashing. The Iron content is determined by flame

atomic absorption spectrometry-procedures( AAS) or by Inductively coupled plasma atomic

emission spectroscopy (ICP-AES) also refered as Inductively Coupled Plasma Optical


Key steps

Preparation



Homogenization






preparation)

Separation from Matrix









for AAS.


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Methods of analysis

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Detection



Wavelength 248,3 nm


Wavelength 271,441 nm; Interferences: none Limit of Quantification: (axial

viewing non ; radial viewing non )

Wavelength 259,940 nm ; Co interferences; Limit of Quantification: (axial

viewing 2 ; radial viewing 6)

Wavelength 238,204 nm, Co, interferences ; Limit of Quantification: :

(axial viewing 3 ; radial viewing 14)

Quantification

o AAS


quantification verified. The content of Iron in sample is determined




o ICP OES


background correction). The content of Iron in sample is determined

from linear regression method using blank, standard solutions and ,

internal standards.

Criteria for analytical performance and Analytical

Quality control


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Methods of analysis

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Method Performance

Table 9. Relevant parameters obtained by inter laboratory studies (blank spaces results were not satisfactory)

Matrix

Standard/Matrix

Liver

paste

Apple

sauce

Minced

fish

Wheat

bran

Milk

powder

Composite

diet D/E

EN

14082

Repeatability

RSDr%

1,8

Reproducibility

RSDR (%)

4,2 *

6,0* 12* 6,9* 8,0* 3,5*

AOAC

999.11

Repeatability

RSDr%

5.3 1.8

Reproducibility

RSDR (%)

7.5 6.8 6.8 8.0 3.5


bran

Milk

powder

Diets

AOAC

999.10

Repeatability

RSDr%

1.6 - - 3.4 4.0

Reproducibility

RSDR (%)

4.8 5.3 9.1 4.8 9.3 5.3

EN

14084

Repeatability

RSDr%

5.6

4,2 4,0

Reproducibility

RSDR (%)

6,7 8,2

18 8,6

5,7


Table 10. List of Reference Materials available in 2008

NIST 2384 Baking chocolate

NIST2387 Peanut Butter

GBW 08552 Freeze Dried Pork Muscle

NIST 1546 Meat Homogenate

NIST 8415 Whole Egg Powder (reference value)


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Methods of analysis

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BCR 679 Freeze-Dried White Cabbage

GBW 07605 Tea

NIST 1567a Wheat flour


NIST 2383 Baby Food (reference value)

NIST 8433 Corn Bran (reference value)

NIST 8436 Durum Wheat Flour (reference value)

VMA 195 Cereal

NIST 1548a Freeze dried mixed diet

NIST 1846 Infant Formula

NIST 8435 Whole milk powder

NRDCDORM 2 Freeze-Dried DogFish Muscle

NIST 1549 Non-Fat Milk Powder

NIST 1566b Freeze –Dried Oyster Tissue

NIST 1946 Fish Tissue

BCR 422 Freeze dried Cod Muscle

NIST 1577b Freeze dried bovine liver

NIST 8418 wheat gluten

NRCDOLT3 Freeze dried dog fish liver


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Methods of analysis

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water, vegetable oil, fat vegetable, fish oil, wine, liqueurs, cognac, diet

food, baby food, olive oil, plants, meat, tuna fish, cheese processed,

meat products, dietary supplements






Absorption Spectrophotometry after microwave digestion



Table 11. CodexStan 234-1999)-Recommended methods of analysis

Matrix


Cocoa butters AOAC 990.05

ISO 8294:1994

IUPAC 2.631


Atomic absorption

spectrophotometry(direct

graphite furnace)

II

Cocoa butters BS 684 Section 2.17:1976 Colorimetry III

Fats and oils AOAC 990.05

ISO 8294:1994

IUPAC 2.631


Atomic absorption

spectrophotometry

(direct graphite furnace)

II

Fruit juices IFJU Method No 15, 1964 Photometry II

Milk products NMKL 139 (1991) (Codex

general method

Atomic absorption

spectrophotometry

II



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Methods of analysis

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Milk products IDF Standard 103A:1986


1995)

Photometry

(bathophenanthroline)

IV

Vinegar IFJU Method No 15, 1964 Photometry IV

dissolved in Natural

mineral waters


1995)

Spectrophotometry II

Remarks

Old Data

o Colorimetric methods are available and described in same tables


o According with (Deharveng, 1999) methods give similar results. Contamination

with dust resulting in a high variability

References









INTERNATIONAL , 83 (5), 1204-1211



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Methods of analysis

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(iv) Magnesium

(v)

Magnesium (Mg) belongs to group II of the third period of the Periodic Table of Elements, a

group that includes two other physiologically important elements: calcium and zinc. Mg has an

atomic weight of 24.312; its atomic number is 12; its valency 2.

Golden Standard






magnesium and calcium by flame atomic absorption spectrometry (AAS) after microwave

digestion

Method Indicator

Name

Code

Scope

Determination of Magnesium in foodstuffs in all relevant matrix successfully tested in

laboratory proficiency testing.

Principle


removed by microwave digestion. The Magnesium content is determined by flame atomic

absorption spectrometry-procedures( AAS) or by Inductively coupled plasma atomic emission


_________________________________________________________________________________

Methods of analysis

31/70

spectroscopy (ICP-AES) also refered as Inductively Coupled Plasma Optical Emission

Spectrometry (ICP-OES).

Key steps

Secção 1.04

Preparation



Homogenization





homogenisation( EN 13804:2002) is the reference standard for sample

preparation

Separation




conventional or microwave assisted heating. (EN 13805). The method is

described for AAS and ICP OES.

Detection



Wavelength 285.5 nm


Wavelength 279,078 nm; Interferences: Fe ;Limit of Quantification: (radial

viewing 33 ; axial viewing 19 )


_________________________________________________________________________________

Methods of analysis

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Wavelength 279,553 nm; Interferences: Fe ;Limit of Quantification: (radial

viewing 1; axial viewing 7

Wavelength 285,213 nm ; Cr interferences; Limit of Quantification: (radial

viewing 4 ; axial viewing 14)

Quantification

o AAS


quantification verified. The content of Magnesium in sample is

determined from calibration curve by plotting (absorbance (A) peak

area ) against concentration. The calibration curve is prepared with at

least five points using concentrations of standard solutions within

working range.

o ICP OES


background correction). The content of Magnesium in sample is



Criteria for analytical performance and Analytical Quality control

Method Performance

Table 12. Relevant parameters obtained by EN 15505 inter laboratory studies

Matrix

Parameter

Simulated

Diet(D)

Simulated

Diet(F)

Milk

Powder

Flash

muscle

Apple Choolate

cake

Mean values

mg/kg

665 618 859 749 251 284

RSDr (%) 3.8 4.4 2.1 2.4 2.1 2.0

RSDR (%) 6.9 6.9 4.6 6.8 4.5 4.0


_________________________________________________________________________________

Methods of analysis

33/70








NIST 1546 Meat Homogenate(reference value)


BCR 381 Rye Flour

GBW 07605 Tea






NIST 8436 Durum Wheat Flour(reference value)

VMA 195 Cereal

VMA 399 Cereal




NIST 8435 Whole Milk Powder(reference value)










_________________________________________________________________________________

Methods of analysis

34/70


o 17 datasets are register at eptis and the following matrix:

Wine, dietary supplements, diet food, baby food, fruit juice, plants,

cheese processed, meat products,


Table 14. Codex Recommended methods of analysis

Matrix


Natural mineral waters ISO 6059:1984 (confirmed

1995)

Titrimetry II

Natural mineral waters ISO 7980:1986(confirmed

1995)

Atomic absorption

spectrophotometry

III

NMKL no 147 (2003). Magnesium and calcium; determination in foodstuffs using flame

atomic absorption spectrometry after microwave oven digestion.

Remarks

Old Data

o Colorimetry is described.


o Methods for magnesium are compatible (Deharveng,1999)

References









_________________________________________________________________________________

Methods of analysis

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- Determination of several elements in

duplicate meals from catering establishments using closed vessel microwave digestion

with inductively coupled plasma mass spectrometry detection: Estimation of daily

dietary intake Food Additives and Contaminants 20 (1), 44-56.

Julshamn, K., Maage, A., Wallin, H.C., Lierhagen, S., Nielsen, J., A sbø, E., Engman, J.,

(...), Niemi, E.(1998). Determination of Magnesium and Calcium in Foods by Atomic

Absorption Spectrometry after Microwave Digestion: NMKL. Journal of AOAC

International 81 (6), 1202-1208



_________________________________________________________________________________

Methods of analysis

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(i) Phosphorus

Phosphorus is an element of group 5 of the periodic table and has an atomic weight of 30.97.

It is one of the most abundant elements on earth, most commonly found as the phosphate ion

(PO43-), with phosphorus in its pentavalent form.

Golden Standard





ISO 9874:2006 Milk -- Determination of total phosphorus content -- Method using molecular

absorption spectrometry

AOAC - 984.27 Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus, Potassium,

Sodium, and Zinc in Infant Formula- Inductively Coupled Plasma Emission Spectroscopic

Method

Scope

Determination of Phosphorus in foodstuffs in all relevant matrix successfully tested in

laboratory proficiency testing

Principle


removed by microwave digestion or by dry ashing. The total Phosporus content is determined

by Spectrophotometric method or by Inductively coupled plasma atomic emission spectroscopy

(ICP-AES) also refered as Inductively Coupled Plasma Optical Emission Spectrometry (ICP-

OES).

Key steps

Preparation



http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=42702


_________________________________________________________________________________

Methods of analysis

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Homogenization






preparation)






method is described for ICP OES.

o Ashing :. Foodstuffs are heated at 470ºC in an oven during 24-48h and reduced to ashes

(organic ingredients and water were removed and carbon is not present). Ashes are treated

with conc. HCl and taken to dryness in a water bath. The solid residue is dissolved with 10%

HNO3 acid and boiled in a water bath during 5 min, avoiding the orthophosphates hydrolysis

that produce coloured solutions. After cooling to room temperature, ashes are transferred to

a volumetric flash and diluted with water (1:2).

Detection

o Phosphorus content is determined by Spectrophotometric method UV-Vis

double-beam at 430nm


Wavelength 177,434 nm; Interferences: Cu Limit of Quantification: (radial


Wavelength 213,618 nm ; Co,Cu,Fe,Mo,Zn interferences; Limit of

Quantification: (radial viewing 4 ; axial viewing 3 )


_________________________________________________________________________________

Methods of analysis

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Quantification.


quantification verified. The content of phosphorous in sample is




working range.

Criteria for analytical performance and Analytical

Quality control

Method Performance

Table 15. Relevant parameters obtained during inter laboratory studies

AOAC 986.24

Infant Formula

Spectrophotometric

method

Parameter Enteral RTF

soy

RTF

soy

Soy

powder

Whey

powder

Mean

Parameter

541 526 447 3908 2350

RSDr% 3.0 2.4

RSDR% 3.5 3.7 11 3.4 31



LGC 7104- Sterilized cream

NIST 2381 Baking chocolate




NIST 1546 Meat Homogenate (reference value)



_________________________________________________________________________________

Methods of analysis

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GBW 07605 Tea

LGC 7103 Sweet digestive Biscuit



NIST 2383 Baby Food

NIST 8432 Corn Starch (reference value )

NIST 8433 Corn Barn (reference value )

NIST 8436 Durum Wheat Flour(reference value )

VMA 195 Cereal

VMA 399 Cereal



NIST 1846 Infant Formula (reference value

NIST 8435 Whole Milk Powder(reference value )




NIST 1946 Fish Tissue (reference value )

BCR 487 value ) Freeze Dried Pigs Liver(reference




NIST 8418 wheat gluten (reference value )



o Canned meat, Sewage sludge, vegetable oil (GFAAS), fat vegetable,

(GFAAS), diet food, baby food, fat animal, fish oil, frying oil, Groundnut oil,

diet food, meat products, olive oil, fish oil, frying oil, groundnut oil, colza oil,

milk evaporated, cheese processed, oil, dietary supplements, evaporated

milk



_________________________________________________________________________________

Methods of analysis

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-

Table 17. Recommended methods of analysis CodexStan 234-1999

Matrix


Special foods AOAC 986.24 Colorimetry

(molybdovanadate)

II

Processed cheese

products

IDF Standard 33C: 1987


1994)

AOAC 990.24

Spectrophotometry

(molybdateascorbic

acid)

II

ISO standards

ISO 10540-1:2003 Animal and vegetable fats and oils -- Determination of phosphorus

content -- Part 1: Colorimetric method


content -- Part 2: Method using graphite furnace atomic absorption spectrometry

ISO 9874:2006 Milk -- Determination of total phosphorus content -- Method using molecular

absorption spectrometry

ISO 2294:1974 Meat and meat products -- Determination of total phosphorus content


content -- Part 3: Method using inductively coupled plasma (ICP) optical emission

spectroscopy

ISO 3946:1982 Starches and derived products -- Determination of total phosphorus content

-- Spectrophotometric method

ISO 2962:1984 Cheese and processed cheese products -- Determination of total

phosphorus content -- Molecular absorption spectrometric method









_________________________________________________________________________________

Methods of analysis

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AOAC 986.24- Phosphorus in Infant Formula and Enteral Products Spectrophotometric

Method

Remarks


o Values in tables are compatible according with results reported by Southgate

o Recently Results of FAPAS have demonstrated total Phosphorous determined

buy ICP-OES or and spectrometric method agree

References






Pulliainen TK, Wallin HC. (1996). Determination of total phosphorus in foods by

colorimetry: summary of NMKL collaborative study. J AOAC Int. 79(6):1408-11.

Cook KK.(1997)Extension of dry ash atomic absorption and spectrophotometric

methods to determination of minerals and phosphorus in soy-based, whey-based,

and enteral formulae (modification of AOAC Official Methods 985.35 and

986.24): collaborative study. J AOAC Int. 80(4):834-44.

T. Koizumi, K. Murakami and H. Nakayama et al., (2002), Role of dietary

phosphorus in the progression of renal failure, Biochem Biophys Res Commun

295 :917–921

Catherine M. Sullivan, Janeen B. Leon and Ashwini R. Sehgal 2007

Phosphorus-Containing Food Additives and the Accuracy of Nutrient Databases:

Implications for Renal Patients Journal of Renal Nutrition, 17(5) : 350-354



_________________________________________________________________________________

Methods of analysis

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(ii) Potassium

Potassium in foods is associated with salts of weak organic acids. Various potassium salts, e.g.

KCl, are used in many applications, amongst others as ingredients in foods (e.g. additives), food

supplements and drugs, household chemicals etc. In this opinion, the term potassium refers to

ionic potassium, except where specific potassium compounds are stated. One mmol potassium

is equivalent to 39.1 mg.

Golden Standard





AOAC 984.27- Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus, Potassium,


Method

AOAC 985.35- Minerals in Infant Formula Enteral Products and Pet Foods – Atomic Absorption

Spectrometric Method

(iii)

(iv) Method Indicator

Name

Code

Scope

Determination of Potassium in foodstuffs in all relevant matrix successfully tested in laboratory


Principle


removed by microwave digestion or by dry ashing. The Potassium content is determined by

flame atomic absorption spectrometry-procedures( AAS) or by Inductively coupled plasma


_________________________________________________________________________________

Methods of analysis

43/70

atomic emission spectroscopy (ICP-AES) also refered as Inductively Coupled Plasma Optical


Key steps

Preparation



Homogenization






preparation

Separation









for AAS.

Detection



Wavelength 766.5 nm



_________________________________________________________________________________

Methods of analysis

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Wavelength 766,490 nm; Interferences: Ar, Ba, Mg Limit of Quantification:


Wavelength 769,896 nm ; Ba interferences; Limit of Quantification: (radial

viewing - ; axial viewing (230) )

Quantification

o AAS


quantification verified. The content of Potassium in sample is




working range.

o ICP OES


background correction). The content of Potassium in sample is


solutions and , internal standard


control

Method Performance

Table 18. Relevant parameters obtained in AOAC AAS- 985.35 inter laboratory studies

Matrix

Parameter

Enteral 7 RTF

soy2

RTF

soy(4and 6)

Soy

Powder

(1and5)

Whey

powder 3

Mean (μg/g 1340 1050 840 6390 5080

RSDr% 2.0 2.0

RSD R% 6.8 2.7 2.1 5.6 3.0


_________________________________________________________________________________

Methods of analysis

45/70









LGC 7001 Mackerel Paste



BCR 381 Rye Flour


GBW 07605 Tea








VMA 195 Cereal

VMA 399 Cereal





LGC 7001 Pork Meat











_________________________________________________________________________________

Methods of analysis

46/70



wine, fruit juice, water, milk powder, diet food, plants, canned meat,

cheese processed, dietary supplements,



Matrix

Method Reference Principle

Food grade salt ESPA/CN-E/104-1994

(applicable to products containing _2 mg-

K/kg)

Flame atomic absorption

spectrophotometry

Food grade salt ESPA/CN-E/103-1994

(applicable to products containing _100 mg-

K/kg)

Titrimetry

Special foods ISO 8070:1987(confirmed 1992)

IDF Standard 119A:1987

Flame emission

spectrophotometry

Special foods AOAC 984.27 ICP emission

spectrometry

Remarks

Old Data

o AOAC 969.23 - Flame Photometric Method Sodium and Potassium in Seafood

o IDF-ISO-AOAC 990.23 - Flame Emission Spectrometric Method- Sodium and

Potassium in Dried Milk




_________________________________________________________________________________

Methods of analysis

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o All methods give similar results.(Southgate, 2002)

o Flame photometry can be used with very good results demonstrated in PT

schemes although mutual interference from phosphorus can occur(Chen

2005)

References




Cook KK. (1997). Extension of dry ash atomic absorption and spectrophotometric

methods to determination of minerals and phosphorus in soy-based, whey-based, and

enteral formulae (modification of AOAC Official Methods 985.35 and 986.24):

collaborative study. J AOAC Int.;80(4):834-44



Dwyer JT, Holden J, Andrews K, Roseland J, Zhao C, Schweitzer A, Perry CR, Harnly

J, Wolf WR, Picciano MF, Fisher KD, Saldanha LG, Yetley EA, Betz JM, Coates PM,

Milner JA, Whitted J, Burt V, Radimer K, Wilger J, Sharpless KE, Hardy CJ. (2007).

Measuring vitamins and minerals in dietary supplements for nutrition studies in the USA

Anal Bioanal Chem.;389(1):37-46. Epub 2007 Jul 20. Review.

Haytowitz, D.B. Pehrsson P. R. and Holden JM. The National Food and Nutrient

Analysis Program: A decade of progress (2008) Journal of Food Composition and

Analysis, 21, Supplement 1, S94-S102.

Chen,M.-J. Hsieh, YT, Weng Y-M, Chiou R. Y.-Y. (2005). Flame photometric

determination of salinity in processed foods Food Chemistry, 91, (4) 765-770.

.

Secção 1.05 EuroFIR assistance to this method/guidelines


_________________________________________________________________________________

Methods of analysis

48/70

(i) Selenium

Foods contain a number of different selenium forms. In animal foods, there are specific

selenium proteins where selenium is incorporated via selenide as selenocysteine, while

selenomethionine, and possibly also selenocysteine to some extent, are non-specifically

incorporated as analogues to methionine and cysteine in foods both of animal and plant origin.

Selenomethionine, as well as the inorganic forms selenite and selenate, are the most common

forms in food supplements and fodder additives. Although extensively used for research

purposes, it is uncertain if the inorganic forms occur in foods. In addition to these forms a

number of uncharacterised forms exist, e.g. in fish (Åkesson and Srikumar, 1994), but their

contribution to total dietary selenium is unknown.

Selenium forms used in supplements are inorganic selenite and selenate and organic selenium

in then form of selenomethionine, selenocystine and selenium enriched yeast. The forms of

selenium found in yeast vary according to production process and the selenomethionine has

been suggested to comprise 20 to 50% of the selenium and that some is bound as

selenotrisulphides (SCF, 1999).


_________________________________________________________________________________

Methods of analysis

49/70

Fig1 Selenium Compounds and their structural formula (Dumont, 2006)


_________________________________________________________________________________

Methods of analysis

50/70

Fig 2 Selenium Compounds and their structural formula (Dumont, 2006)


_________________________________________________________________________________

Methods of analysis

51/70

Fig 3 Selenium Compounds and their structural formula (Dumont, 2006)

Golden Standard

EN 14627:2005 Foodstuffs - Determination of trace elements - Determination of total arsenic

and selenium by hydride generation atomic absorption spectrometry (HGAAS) after pressure

digestion

Codex-Adopted-AOAC -986.15 Arsenic, Cadmium, Lead, Selenium, and Zinc in Human and Pet

Foods Spectroscopy/Atomic Absorption Spectroscopy, Anodic Stripping Voltammetry


_________________________________________________________________________________

Methods of analysis

52/70

Scope

Determination of Total Selenium in both inorganic species (IV and VI) in foodstuffs in all

relevant matrix successfully tested in laboratory proficiency testing. The method is not

applicable for determination of organoselenium compounds

Principle

These techniques use wet-sample digestion (e.g., nitricperchloric acid) to destroy organic

matter. Sample reduction to convert Se(VI) (+6 valence state) to Se(IV) (+4 valence state) is

necessary prior to using sodium borohydride to reduce all selenium present to selenium hydride

The selenium hydride is thermally decomposed and atomized in the sample beam of the atomic

absorption spectrophotometer. Nitric-perchloric acid is commonly used for the digestion step.

Because perchloric acid is potentially explosive, use of phosphoric acid instead is also

common..

Key steps

Preparation



Homogenization


grinder; stainless steel vegetable slice; plastic salad spinner and homogenised;)




preparation)

Extraction

Sample decomposition was performed by the microwave digestion Samples were

prepared by digesting in microwave furnace with nitric acid and peroxide and water .

The microwave conditions are settled according with matrix type. After cooling and

filtration, each solution was made up to reference volume with water heated with

pp p t d m t f H w t th 6 ∞


_________________________________________________________________________________

Methods of analysis

53/70

Detection

The following instrumental parameters were used:

Wavelength = 196.0 nm

SBW = 1.0 nm

Hollow Cathode Lamp Current = 10 mA

Integration Time 25 seconds

Peak Height or Peak Area

Background Correction

Recorder Fast (0.1 second response time)

Lean Air Acetylene Flam

Quantification


quantification verified. The content of Selenium IV and VI in sample is

determined from calibration curve by plotting (absorbance (A) peak area )

against concentration. The calibration curve is prepared with at least five



control







BCR 381 Rye Flour











_________________________________________________________________________________

Methods of analysis

54/70


NRCDORM 2 Freeze Dried Dogfish Muscle





BCR 422 Freeze Dried Cod Muscle



NRCDOLT 3 Freeze Dried Dogfish Liver



diet food, wheat, milk powder, vegetables, water, premix,


A variety of analytical methods can be used to determine trace concentrations (ng/g) of

selenium in biological tissues. These include fluorometry, neutron activation analysis (NAA),

atomic absorption spectroscopy (AAS), inductively coupled plasma-atomic emission

spectroscopy (ICP-AES), inductively coupled plasma-mass spectrometry (ICP-MS), gas

chromatography (GC), spectrophotometry, x-ray fluorescence analysis, and other


Matrix


Natural mineral waters AOAC 986.15 Atomic absorption

spectrophotometry

II

AOAC 996.17-Selenium in Feeds and Premixes Hydride Generation Atomic Absorption

Spectroscopy

(ii) Selenium speciation

Hyphenated Techniques for Element Speciation



_________________________________________________________________________________

Methods of analysis

55/70

Selenium attracted the greatest interest with regard speciation, the possible role of this

element in the prevention of certain forms of cancer and other diseases. According with

Cubadda essential selenium species will be listed on food composition labels.

(iii)

Selenium speciation has become a prominent topic of present research in food science to

gain information on bioavailability, essentility, or toxicity of element present in food.

HPLC-ICP-MS has gained the highest popularity for the purpose of speciation. Prior to

the introduction into plasma the different chemical species are separated from one

another using different chromatographic principles exploited size –exclusion, reverse-

phase, ion-exchange in a combination of column and mobile phase, precede by

appropriate extraction procedures (Cubadda,2004). This methodology is preceded by

extraction techniques the results obtained depended critically on the sample

preparation procedure used (Soxhelet, room temperature mixing, sonication etc). The

preservation of species identity is another problem. The unavailability of Certified

references materials and interlaboratory collaborative studies and other quality tools

are pitfalls that make difficult at present to include results from speciation into Food

composition Databanks. Although Selenium speciation is a very important topic that

need to be followed by compilers and those involved with data compilation process.

The work of Wayne Wolf in USDA should be followed with attention because is one of

the groups where research in selenium speciation is orientated to food composition

data.

Remarks total selenium

The use of hydride generation with a normal acid sodium tetrahydroborate reaction provides

exceptional sensitivity with continuous flow hydride generators. In some situations there are

interferences which will mask the sensitivity. An alternative chemistry system using alkaline

solutions is the possibility of simultaneous removal of seriously interfering elements such as

nickel and copper as the hydroxides.

In order cases when samples has Se(VI) is not reducible by tetrahydroborate and Se(IV) it

is possible to distinguish between Se(VI) and Se(IV) in such samples, because Se(IV) can

be determined separately and, after a chemical reduction of Se(VI) to Se(IV), the total

concentration of selenium (that is Se(IV) + Se(VI)) can be determined. However, if a sample

is acidified before the analysis (for instance for preservation purposes), this reaction is likely

to take place within the time of analysis, prohibiting the possibility of determining both


_________________________________________________________________________________

Methods of analysis

56/70

oxidation forms. Standard solutions should therefore be subjected to the same reduction

process as the samples to ensure that all selenium is present as SeIV. All standard and

sample solutions should be cooled to room temperature before analysis

For an effective release of the gaseous hydrides some parameters are of importance: the

sample acidity, the concentration and the flow of reducing agent (tetrahydroborate)

Incomplete destruction of organic matter and losses caused by volatilisation of selenium

can produced low recoveries

Latest Review

o Dumont E, Vanhaecke F, Cornelis R. 2006 Selenium speciation from food

source to metabolites: a critical review. Anal Bioanal Chem.;385(7):1304-23.

Review

On Going Research Project:

o Methods for Identification and Determination of S and Se Containing

Compounds in Foods : (2004-2009)USDA


Depends on method specificity

Commonly used instrumental methods to measure inorganic selenium include hydride

generation coupled with either atomic absorption spectrometry (HG-AAS) or with

inductively coupled plasma emission spectrometry (HG-ICPES) [5,6], graphite furnace

atomic absorption spectrometry (GFAAS) differential pulse polarography (DPP) and

cathodic stripping voltammetry .

The selenium content in fish requires a digestion method that is extremely thorough in

decomposing organic matter, and yet does not result in conditions under which

selenium is lost.

Lambert ( 2000) analysed several methods for digestion they concluded AOAC

method produced acceptable results


_________________________________________________________________________________

Methods of analysis

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References

Arnault I,Auger J. (2006) Seleno-compounds in garlic and onion. J Chromatogr.

21;1112(1-2):23-30

Dumont E, Ogra Y, Vanhaecke F, Suzuki KT, Cornelis R. Anal Bioanal Chem. 2006

Liquid chromatography-mass spectrometry (LC-MS): a powerful combination for

selenium speciation in garlic (Allium sativum). Mar;384(5):1196-206. Epub 2006 Jan 25.

Tinggi, U(1999) Determination of selenium in meat products by hydride generation

atomic absorption spectrophotometry.J-AOAC-Int. 82 (2) 364-367

Cubadda, F (2004). Inductively Coupled Plasma- Mass Spectrometry for determination

of elements and elemental species in food: A review. Journal AOAC, 87 (1) 173-204.

Pedrero Z, Elvira D, Cámara C, Madrid Y. (2007) .Selenium transformation studies

during broccoli (Brassica oleracea) growing process by liquid chromatography-

inductively coupled plasma mass spectrometry (LC-ICP-MS). Anal Chim

Acta.;596(2):251-6.

Wolf WR, Goldschmidt RJ. Updated estimates of the selenomethionine content of NIST

wheat reference materials by GC-IDMS. Analytical and Bioanalytical Chemistry.

2007;387(7):2449-52.

Yang L, Sturgeon RE, Wolf WR, Goldschmidt RJ, Mester Z. Determination of

selenomethionine in yeast using CNBr derivatization and species specific isotope

dilution GC ICP-MS and GC-MS. Journal of Analytical Atomic Spectrometry.

2004;19(11):1448-53.

Wolf WR, Goldschmidt RJ. Selenomethionine contents of NIST wheat reference

materials. Analytical and Bioanalytical Chemistry. 2004;378(5):1175-81.



_________________________________________________________________________________

Methods of analysis

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(iv) Sodium

Sodium (Na) is a metal with an atomic mass of 23. It is found widely in nature and as a normal

constituent of foods. It is added to foods, most frequently as sodium chloride (NaCl), common

known as salt (1 mmol is equivalent to 23 mg sodium and approximates 58 mg sodium

chloride), but also as other salts, e.g. nitrate, nitrite, phosphates, glutamate. In drinking water,

the guide level of sodium is 20 mg/L (Council Directive 80/778/EEC)

Golden Standard


magnesium and calcium by flame atomic absorption spectrometry (AAS) after microwave

digestion

NKML 180, 2005 Sodium. Determination in Foodstuffs by Flame Atomic Absorption

Spectrometry after Microwave Digestion

AOAC 984.27 -Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus, Potassium,


Method

Method Indicator

Name

Code

Scope

Determination of Sodium in foodstuffs in all relevant matrix successfully tested in laboratory


Principle


removed by microwave digestion, or dry washing. The Sodium content is determined by flame

photometry (FF),flame atomic absorption spectrometry-procedures( AAS) or by Inductively

coupled plasma atomic emission spectroscopy (ICP-AES) also refered as Inductively Coupled

Plasma Optical Emission Spectrometry (ICP-OES).


_________________________________________________________________________________

Methods of analysis

59/70

Key steps

Preparation



Homogenization






preparation

Separation






o Dry ashing : Sample in a crucible made by platinum is incinerated heating



for AAS and FF

Detection



Wavelength 589.6 nm


Wavelength 330,235 nm; Interferences: Zn Limit of Quantification: (radial


Wavelength 588,995 nm ; Ar, V interferences; Limit of Quantification: (radial


Wavelength 589,592 nm ; Ba interferences; Limit of Quantification: (radial



_________________________________________________________________________________

Methods of analysis

60/70

Quantification

o AAS


quantification verified. The content of Sodium in sample is determined




o ICP OES


background correction). The content of Sodium in sample is




control

Method Performance

NMKL interlaboratory study (Julshamn K, Lea P, Norli HS, 2005)

Nine laboratories participated in an interlaboratory method performance (collaborative) study of

a method for the determination of sodium in foods by flame atomic absorption spectrometry

after wet digestion, using a microwave oven technique. The method was tested on a total of 6

foods (broccoli, carrot, bread, saithe fillet, pork, and cheese) with sodium concentrations of

1480-8260 mg/kg. The repeatability relative standard deviations (RSDr) for sodium ranged from

1.9 to 6.5%. The reproducibility relative standard deviations (RSDR) ranged from 4.2 to 6.9%.

The HorRat values ranged from 0.9 to 1.6.


_________________________________________________________________________________

Methods of analysis

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Table 23. List of CRM/SRM available







LGC 7001 Mackerel Paste



BCR 381 Rye Flour


GBW 07605 Tea








VMA 195 Cereal

VMA 399 Cereal





LGC 7001 Pork Meat











_________________________________________________________________________________

Methods of analysis

62/70



wine, water, milk powder, canned meat, fruit juice, plants, premix,

cheese processed, meat products, dietary supplement


AOAC 984.27- Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus, Potassium,


Method

AOAC 985.35- Minerals in Infant Formula Enteral Products and Pet Foods – Atomic

Absorption Spectrometric Method

AOAC 969.23 - Flame Photometric Method Sodium and Potassium in Seafood

IDF-ISO-AOAC 990.23 - Flame Emission Spectrometric Method- Sodium and Potassium in

Dried Milk

Table 24. CodexStan Recommended methods of analysis

Component Matrix

Method Reference Principle

Sodium Special foods ISO 8070:1987(confirmed

1992) IDF Standard

119A:1987

Flame emission

spectrophotometry

Sodium Special foods AOAC 984.27 ICP emission

spectrometry

Sodium

chloride

Bouillons and consommes AOAC 971.27 (Codex

general method)

Potentiometry

Sodium

chloride

Food grade salt Described in the Standard Calculation

Sodium

chloride

Margarine AOAC 971.27 (Codex

general method)

Potentiometry

Sodium

chloride

Minarine AOAC 971.27 (Codex

general method)

Potentiometry

Sodium

chloride

Processed tomato

concentrates

AOAC 971.27(Codex

general method)

Potentiometry



_________________________________________________________________________________

Methods of analysis

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Sodium

chloride

Quick frozen blocks of fish

fillet,

minced fish flesh and

mixtures of

fillets and minced fish flesh

AOAC 971.21 (Codex

general method)

Potentiometry

Sodium

chloride

Quick frozen fish sticks (fish

fingers)

and fish portions - Breaded

or in batter

AOAC 971.27 (Codex

general method)

Potentiometry

Salt Butter IDF Standard 179:1997

AOAC 971.27 (Codex

general method)

Potentiometry

(determination of

chloride, expressed

as sodium

chloride)

Salt Processed cheese products IDF Standard 88A:1979


1996)

AOAC 983.14

Potentionmetry

(determination of

chloride, expressed

as sodium

chloride)

Salt in brine Pickled cucumbers AOAC 971.27(Codex

general method)

Potentiometry

Salt in brine Table olives AOAC 971.27(Codex

general method)

Potentiometry

Salt, added Fruit juices AOAC 971.27 (Codex

general method)

Potentiometry

Salt, added Fruit juices IFJU Method No 37, 1968 Electrochemical

titrimetry

Salt Butter IDF Standard 12B: 1988

ISO 1738:1997

AOAC 960.29

Titrimetry (Mohr:

determination of

chloride, expressed

as sodium

chloride)

Remarks



_________________________________________________________________________________

Methods of analysis

64/70

o All the methods give comparable results

o Flame photometry can be used with very good results demonstrated in PT

schemes although mutual interference from calcium can occur(Chen 2005)

o Overestimation of sodium concentration is reported in foods with low level of

sodium when analysis are carried out by ICP-OES

References




Julshamn K, Lea P, Norli HS.(2005).Determination of sodium in foods by flame atomic

absorption spectrometry after microwave digestion: NMKL interlaboratory study. J

AOAC Int. 88(4):1212-6.

Cook KK. (1997). Extension of dry ash atomic absorption and spectrophotometric

methods to determination of minerals and phosphorus in soy-based, whey-based, and

enteral formulae (modification of AOAC Official Methods 985.35 and 986.24):

collaborative study. J AOAC Int.;80(4):834-44

Chen,M.-J. Hsieh, YT, Weng Y-M, Chiou R. Y.-Y. (2005). Flame photometric

determination of salinity in processed foods Food Chemistry, 91, (4) 765-770



_________________________________________________________________________________

Methods of analysis

65/70

(v) Zinc

Zinc has an atomic weight of 65.37 and is classified as a group IIB post-transition

metal. Zinc is also present in foods and supplements as salts of the divalent cation (Zn2+

)

Golden Standard







digestion



ashing

i. Method Indicator

Name

Code

Scope

Determination of Zinc in foodstuffs in all relevant matrix successfully tested in laboratory


Principle


removed by microwave digestion or by dry ashing. The Zinc content is determined by flame

atomic absorption spectrometry-procedures( AAS) or by Inductively coupled plasma atomic

emission spectroscopy (ICP-AES) also refered as Inductively Coupled Plasma Optical



_________________________________________________________________________________

Methods of analysis

66/70

Key steps

Preparation



Homogenization






preparation)










for AAS.

Detection



Wavelength 213,9 nm


Wavelength 213,857 nm; Interferences: Cu, Fe, Ni; Limit of Quantification:

(axial viewing 3,3 ; radial viewing 1)

Wavelength 206,200 nm and Cr interferences; Limit of Quantification: (axial

viewing 13 ; radial viewing 5)


_________________________________________________________________________________

Methods of analysis

67/70

Wavelength 202,548 nm and Cr, Cu, Co,Ni interferences ; Limit of

Quantification: (radial viewing 3)

Quantification

o AAS


quantification verified. The content of Zinc in sample is determined




o ICP OES


background correction). The content of Zinc in sample is determined

from linear regression method using blank, standard solutions and ,

internal standards.


control

Method Performance

Table 25. AAS relevant parameters obtained during inter-laboratory

Matrix

Standard/Matrix

Liver

paste

Apple

sauce

Minced

fish

Wheat

bran

Milk

powder

Composite

diet D/E

EN

14082

Repeatability

RSDr%

1,8

Reproducibility

RSDR (%)

4,2 *

6,0* 12* 6,9* 8,0* 3,5*

AOAC

999.11

Repeatability

RSDr%

5.3 1.8

Reproducibility

RSDR (%)

7.5 6.8 6.8 8.0 3.5


bran

Milk

powder

Diets


_________________________________________________________________________________

Methods of analysis

68/70

AOAC

999.10

Repeatability

RSDr%

1.6 - - 3.4 4.0

Reproducibility

RSDR (%)

4.8 5.3 9.1 4.8 9.3 5.3

EN

14084

Repeatability

RSDr%

1,6

3,4

4,0

Reproducibility

RSDR (%)

4,8

5,3

4,8

9,3

5,3


Table 26. List of available CRM/SRM in 2007










BCR 679 Freeze Dried White Cabbage

BCR 381 Rye Flour

GBW 07605 Tea








VMA 195 Cereal

VMA 399 Cereal





_________________________________________________________________________________

Methods of analysis

69/70


LGC 7001 Pork Meat


NRCDORM 2 Freeze Dried Dogfish Muscle





BCR 422 Freeze Dried Cod Muscle





NRCDOLT 3 Freeze Dried Dogfish Liver



water,wine, diet food, wheat, milk powder, vegetables, tuna fish,

vegetal, dietary supplement






Absorption Spectrophotometry after microwave digestion (Zn> 4 mg/kg)





_________________________________________________________________________________

Methods of analysis

70/70

Table 27. Codex Stan Recommended methods of analysis

Matrix


Fruit juices AOAC 969.32 Codex general

method)

Atomic absorption

spectrophotometry

II

Fruit juices AOAC 986.15 (Codex general

method)

Atomic absorption

spectrophotometry

III

Vinegar AOAC 969.32(Codex general

method)

Atomic absorption

spectrophotometry

II

Remarks

Old Data .

o AOAC 944.09 – Colorimetric Zinc in Food


o AAS and ICP are better techniques than colorimetric (Southgate, 2002)

o Contamination can be the major problem. The acids used should be highest

analytical quality. All glassware and plastic used should be cleaned and rinsed

according with EN 13804:2002.

Results are express frequently as weight of the element on sample dry weight, and

information on water content and method used to determine sample humidity need to

be given.

References






INTERNATIONAL , 83 (5), 1204-1211


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