CCQM-K89 Trace and Essential Elements in Herba Ecliptae · CCQM-K89 Trace and Essential Elements in...

CCQM-K89

Trace and Essential Elements in Herba Ecliptae

Final Report

Authors: Liliana Valiente (INTI)1, David Saxby, Jeffrey Merrick (NMIA)2, Boriana Kotzeva (BIM)3, Zoltan Mester, Lu Yang, Scott Willie (NRC)4, Liuxing Feng, Jun Wang (NIM)5, Guillaume Labarraque (LNE)6, Olaf Rienitz (PTB)7, Della Wai-mei Sin, Chuen-sing Mok, Siu-kay Wong, Chi-shing Ng, Wai-hong Fung, Ho-pan Yau (GLHK)8, Yanbei Zhu (NMIJ)9, Yong-Hyeon Yim, Kyoung Seok Lee, In Jung Kim, Young Ran Lim (KRISS)10, Pedro Ramirez Cruz, Flora E. Mercader Trejo, Edith Valle Moya, Itzel Santiago Castellanos, Maria del Rocio Arvizu Torres, Judith Velina Lara Manzano (CENAM)11, L.A. Konopelko, Yu A. Kustikov (VNIIM)12, Richard Shin (HSA)13, Milena Horvat, Radojko Jacimovic, Radmila Milacic (JSI)14, Charun Yafa, Sutthinun Taebunpakul, Nattikarn Kaewkhomdee, Pranee Phukphatthanachai (NIMT)15, Oktay Cankur, F. Gonca Coskun (TUBITAK UME)16, Gregory C. Turk, W. Clay Davis, Laura J. Wood, Karen E. Murphy (NIST)17, John Entwisle (LGC)18 1 Instituto Nacional de technologia Industrial, Argentina 2 National Measurement Institute, Australia 3 Bulgarian Institute of Metrology, Bulgaria 4 National Research Council of Canada 5 National Institute of Metrology, P.R. China 6 Laboratorie national de metrologie et d’essais, France 7 Physikalisch-Technische Bundesanstalt, Germany 8 Government Laboratory, Hong Kong, China 9 National Metrology Institute of Japan 10 Korean Research Institute of Standards & Science, Republic of Korea 11 Centro Nacional de Metrologia, Mexico 12 Mendeleyev Institute for Metrology, Russia 13 Health Sciences Authority, Singapore 14 Jozef Stefan Institute, Slovenia 15 National Institute of Metrology (Thailand) 16 National Matrology Institute of Turkey 17 National Institute of Standards and Technology, USA 18 LGC, UK

Abstract

The Key comparison CCQM-K89 was undertaken to demonstrate the capability of participating NMIs and DIs in measuring the contents of incurred trace elements (total arsenic, cadmium and lead) and essential elements (calcium and zinc) at µg/g (for arsenic, cadmium, lead and zinc) and mg/g (for calcium) levels in herb matrix sample by various analytical techniques. This key comparison was organized by the Government Laboratory of the Hong Kong Special Administrative Region (GLHK) and agreed at the Inorganic Analysis Working Group Meeting in Hindås, Sweden in October 2010 as a benchmarking exercise with Arsenic (a trace element) and Calcium (an essential element) chosen as the “exemplary” elements. It was also agreed that a pilot study CCQM – P126 would be run in parallel with this key comparison. The key comparison serves to facilitate claims by participants on the Calibration and Measurement Capabilities (CMCs) as listed in Appendix C of the Key Comparison Database (KCDB) under the Mutual Recognition Arrangement of the International Committee for Weights and Measures (CIPM MRA). Totally 20 NMIs/DIs registered for this programme and 18 of them submitted their results. Most of the participants used microwave acid digestion methods for sample dissolution. For the instrumental determination, a variety of techniques like ICP-MS, AAS, INAA, ICP-AES were employed by the participants. For this key comparison, inorganic core capabilities have been demonstrated by concerned participants with respect to methods including ICP-MS (without isotope dilution), ID-ICP-MS, ICP-AES, INAA, AAS and ion chromatography with iteratively matrix-matched calibration on the determination of total arsenic, calcium, cadmium, lead and zinc in a matrix of herb.

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Table of Content Page

1 Introduction 2

2 Participating Institutes 3

3 Samples and Instruction to Participants 4

3.1 Material 4

3.2 Homogeneity and stability study 4

3.3 Instructions to participants 6

4 Methods of Measurement 7

5 Results and Discussion 12

5.1 General 12

5.2 Traceability of calibrants used by participants 16

5.3 Calculation of the reference mass fraction values and associated uncertainties

16

5.4 Equivalence statements 24

6 Demonstration of Core Capabilities 30

7 Conclusion 30

Acknowledgement 31

References 31

Appendix 32

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1. Introduction This study is a follow-up to the CCQM pilot study “CCQM-P97: Cadmium and lead in herb (Herba Demodii Styracifolii)” organized by the Government Laboratory of the Hong Kong Special Administrative Region (GLHK) in 2007. The herb Herba Ecliptae was selected as the testing material, which is widely used as a dietary supplement and a traditional herbal medicine (Chinese Materia Medica and Ayurveda product), and is mainly used as a liver tonic, and for treating hair loss and prevention of pre-mature greying of hair. This is the first time that a CCQM key comparison is organised on the analysis of naturally incurred trace elements (total arsenic, cadmium and lead) and essential elements (calcium and zinc) for herbs /dietary supplements. The aim of the study is to demonstrate the capability of participating national metrology institutes and designated institutes in measuring the contents of incurred elements, including arsenic, calcium, cadmium, lead and zinc from µg/g to mg/g levels, in an herbal sample (Herba Ecliptae), using various techniques so as to facilitate their claim on the Calibration and Measurement Capabilities (CMC) as listed in Appendix C of the Key Comparison Database (KCDB) under the Mutual Recognition Arrangement of the International Committee for Weights and Measures (CIPM MRA). Participants are also requested to fill in the “Core Capabilities” (CC) tables as a means of providing evidence for their CMC claims. This key comparison has been selected as a benchmarking exercise at the CCQM IAWG meeting held in Hindås, Sweden in October 2010. Most institutes regularly participating in IAWG studies agreed to take part in the study by analyzing two “exemplary” elements even if they do not normally analyse materials of this type. The “exemplary” elements chosen for this study are Arsenic (a trace element) and Calcium (an essential element). It was also agreed that a pilot study CCQM – P126 would be run in parallel with this key comparison. The Draft A Report for this comparison was circulated among participants prior to the IAWG meeting held on 1-2 Nov 2011 in Sydney. The Meeting discussed the content of the Report and the approach for determination of the key comparison reference values (KCRV) and their associated measurement uncertainties u(KCRV). Based on the comments received afterward on the approach for KCRV calculation and additional findings from participants on their submitted results, the piloting laboratory, GLHK, proposed and the meeting agreed to using the “median” approach for the KCRV calculation in the IAWG meeting held on 9-10 Oct 2012 in Istanbul.

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2. Participating Institutes Totally 20 institutes registered in the Key Comparison CCQM-K89 and the list is given in Table 1 in alphabetic order of the countries’ names of participating NMIs/DIs. Table 1: List of participating NMIs/DIs for CCQM-K89

No. Institute Country Contact person Measurand

1 INTI Instituto Nacional de technologia Industrial Argentina Liliana Valiente As, Ca, Cd,

Pb

2 NMIA National Measurement Institute Australia David Saxby As

3 INMETRO Instituto Nacional de Metrologia, Normalizacao e Qualidade Industrial

Brazil Rodrigo Caciano de Sena As, Ca

4 BIM Bulgarian Institute of Metrology Bulgaria Boriana Kotzeva As, Ca, Cd,

Pb, Zn

5 NRC National Research Council of Canada Canada Zoltan Mester As, Cd, Pb,

Zn

6 NIM National Institute of Metrology, P.R. China China Liuxing Feng As, Ca, Cd,

Pb, Zn

7 LNE Laboratorie national de metrologie et d’essais France Guillaume

Labarraque Cd, Pb, Zn

8 PTB Physikalisch-Technische Bundesanstalt Germany Olaf Rienitz As, Ca

9 GLHK Government Laboratory, Hong Kong, China

Hong Kong, China Chi-shing Ng As, Ca, Cd,

Pb, Zn

10 INRiM Istituto Nazionale di Ricerca Metrologica Italy Luifi

Bergamaschi As

11 NMIJ National Metrology Institute of Japan Japan Yanbei Zhu As, Ca, Cd,

Pb, Zn

12 KRISS Korean Research Institute of Standards & Science

Korea, Republic of Yong-Hyeon Yim As, Ca, Cd,

Pb, Zn

13 CENAM Centro Nacional de Metrologia Mexico Judith Velina

Lara Manzano As, Ca, Cd, Pb, Zn

14 VNIIM Mendeleyev Institute for Metrology Russia L.A. Konopelko As, Ca, Cd,

Pb, Zn

15 HSA Health Sciences Authority Singapore Richard Shin As, Ca, Cd,

Pb, Zn

16 JSI Jozef Stefan Institute Slovenia Milena Horvat As, Ca, Cd,

Pb, Zn

17 NIMT National Institute of Metrology (Thailand) Thailand Charun Yafa As, Ca, Cd,

Pb, Zn

18 TUBITAK UME National Matrology Institute of Turkey Turkey Oktay Cankur As, Ca, Cd,

Pb, Zn

19 NIST National Institute of Standards and Technology USA Gregory C. Turk As, Ca, Cd,

Pb, Zn 20 LGC UK John Entwisle As

Remark: INRiM and INMETRO were not able to submit their results because of some technical problems. INTI did not submit results for Cd and Pb because of instrumental problem.

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3. Samples and Instruction to Participants

3.1. Material Several batches of dry Herba Ecliptae were purchased from the local market in Hong Kong and were confirmed to contain quantities of incurred arsenic, calcium, cadmium, lead and zinc at appropriate levels. The herb was rinsed with distilled water to remove dirt and foreign matters, and then was air-dried in a Class 1000 cleanroom. The dried samples were further freeze dried and grinded to powder. After sieving with a 200 μm sieve and mixing thoroughly, the powdered materials were packed into pre-cleaned and nitrogen-flushed amber glass bottles. The bottled samples, each containing 25 g of powdered sample, were disinfected with γ-irradiation at about 1 kGy, and were each sealed under vacuum with a polypropylene bag. The samples are stored at room temperature (at 20 ºC) before shipment.

3.2. Homogeneity and stability study

The homogeneity study was conducted after the testing material was bottled and irradiated. Ten bottles of the testing material were randomly selected from about 200 bottles. Two test portions of 0.1 g were taken from each bottle for analysis.

The test portions were digested using microwave assisted digestion. The digested samples and reagent blanks were analysed using ICP-MS for As, Cd, Pb and Zn, and ICP-OES for Ca. Quantification was done through external calibration following a validated procedure. ANOVA technique was applied to assess the between bottle heterogeneity and the standard uncertainty originated from the between bottle heterogeneity was calculated using the formula given below in accordance with ISO Guide 35:2006 [1]. The results are summarized in Table 2.

MSwithin

withinbb

2n

MSu

ν⋅= (1)

where ubb standard uncertainty due to between bottles heterogeneity MSwithin mean square of within bottles variance νMSwithin degree of freedom of MSwithin n number of subsamples

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Table 2: Summary of homogeneity study results

Measurand

ANOVA test on heterogeneity

Relative standard uncertainty due to between bottle heterogeneity, ubb (%) F-statistics

Critical value

As 0.973 3.020 1.30 Ca 0.553 3.020 1.37 Cd 1.560 3.020 0.76 Pb 1.794 3.020 1.23 Zn 1.930 3.020 0.50

The homogeneity study results indicate that no significant heterogeneity was observed in the testing material and hence its quality is fit for the purpose of this comparison programme. Long-term and short-term stability studies were conducted for the testing material using the same analytical procedure and sample size as for the homogeneity study. The long-term stability is associated with the behavior of the testing material under storage in participating laboratories while the short-term stability studies aimed to show the stability of the material during its transport. The long-term stability was conducted at 20 ºC over a 5.5-month period starting from the testing material delivery date to the result submission deadline (sampling points: 0 month, 2 months and 5.5 months). The short-term stability was conducted at 45 ºC over a 14-day period (sampling points: 2 days, 7 days and 14 days).

The trend-analysis technique proposed by ISO Guide 35:2006 [1] was applied to assess the stability of the testing material at 20 ºC and 45 ºC as well. The basic model for the stability study is expressed as

Y = β0 + β1X + ε (2)

where β0 and β1 are the regression coefficients, and ε denotes the random error component. With appropriate t-factor, β1 can be tested for significance of deviation from zero. Table 3 summarizes the results of the stability test at 20 ºC and 45 ºC respectively.

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Table 3: Summary of stability test results

Measurand p-value for significance test for β1 20 ºC 45 ºC

As 0.4340 0.6390 Ca 0.3283 0.3082 Cd 0.1417 0.7783 Pb 0.3605 0.0679 Zn 0.4323 0.1830

As all p-values are greater than 0.05, it was concluded that the corresponding β1 value was not significantly deviated from zero at 95% confidence level. In other words, no instability was observed for the testing material at both 20 ºC and 45 ºC during the testing period and hence the testing material is fit for the purpose of the comparison in terms of stability. To monitor the highest temperature that the testing material would be exposed to during the transportation, temperature recording strips were sent along with the testing materials to the participating institutes. According to the information provided by participants in the Sample Receipt Form, the maximum temperature that the testing materials experienced was all below 37 ºC except one at 40 ºC.

3.3. Instructions to participants

Each participant had received one bottle containing about 25 g of dry herbal powder and was requested to perform at least five independent measurements on five separate portions of the testing material and to determine the mass fractions of the measurands. The participants were free to use any analytical methods of their choice, and were advised to mix the testing material thoroughly before processing and the sample size of at least 0.1 g was recommended. For the determination of dry mass correction, a minimum of three separate portions (recommended size to be 1 g each) of the sample was suggested to be taken and placed over anhydrous calcium sulphate in a desiccator at room temperature for a minimum of 10 days until reaching a constant mass. The participants were also advised to carry out dry mass correction and analysis of test sample portions at the same. The participants were asked to report the mean value of at least 5 independent measurements on dry mass basis and its associated uncertainty (combined standard

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uncertainty at 1 sigma level), and the mass fractions of measurands in μg/g for total arsenic, cadmium, lead and zinc, and in mg/g for calcium.

Participants were requested to provide an outline of sample digestion procedures, analytical methods and uncertainty estimation (including measurement equations), full measurement uncertainty budget (including all potential uncertainty components for each measurand and the combined standard uncertainty); and sources and purity of any reference and/or standard materials used.

4. Methods of Measurement

The most used analytical techniques were HR-ICP-MS, ID-ICP-MS, ICP-MS, ICP-OES, and INAA. The digestion method mostly used was microwave assisted digestion. The summary of the reported technical details of the methods of measurement is given in Table 4.

Table 4: Summary of measurement methods used by the participants

Institute Sample preparation/ digestion procedure Measurement technique INTI As

Ca

microwave digestion in closed vessel with HNO3 and H2O2

As GF-AAS (standard addition)

Ca FAAS NMIA As microwave digestion using: 3 mL

HNO3 (69%w/w) + 3 mL H2O2 (30% w/v) confirmation complete digestion using: 3 mL HNO3 (69%w/w) + 3 mL H2O2 (30% w/v) + 1 mL HF (5% w/v)

As ICP-SF-MS (standard addition)

BIM All 1. weighing about 0.3 g testing material into a microwave vessel

2. addition of 10 mL nitric acid. preparation of procedural blanks

3. cold pre-digestion for 4 hrs 4. microwave digestion under operating

conditions (temperature control) 5. sample and standards dilution. All

solutions are gravimetrically prepared

All ICP-MS

NRC All microwave acid digestion As HG-ET-AAS Ca ICP-OES Cd Pb Zn

ICP-MS (ID & reverse ID)

NIM All 1. microwave acid digestion (5 mL HNO3 + 3 mL H2O2 + 0.1 mL HF)

2. temperature raised to 120°C in 5

As ICP-MS (standard addition)

Ca ICP-OES

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min., then to 180°C in 5 min., hold for 30 min.

Cd Pb Zn

Double IDMS

LNE Cd Pb Zn

0.2 g of sample were weighed and digested in a closed microwave oven with 7 mL HNO3 + 1 mL H2O2 + 0.15 mL HF

Cd Pb Zn

Quad-ICP/MS ratio: 112Cd/ 111Cd, 208Pb/206Pb, 68Zn/67Zn

PTB As microwave acid digestion HNO3/HF/H2O2

As HR-ICP-MS (gravimetric standard addition with internal standard)

Ca microwave acid digestion HNO3/H2O2

Ca Ion chromatography (gravimetric matrix-matched bracketing with internal standard)

GLHK All microwave acid digestion As ICP-HRMS (gravimetric standard addition)

Ca ICP-OES (gravimetric standard addition)

Cd Pb

ID-ICP-HRMS

Zn ID-ICP-HRMS NMIJ All 1. 0.3 g sample was taken and added

with 6 mL HNO3 + 2 mL H2O2 with enriched isotope in case of IDMS

2. microwave digestion (ramp: 150°C for 30 min, hold for 5 min.)

3. cooling down and addition of 1 mL HNO3 + 1 mL H2O2 + 0.5 mL HF

4. microwave digestion (ramp: 220°C for 25 min, hold for 20 min.)

5. evaporation of acid 6. addition of 0.6 mL HNO3 7. cooling down and addition of pure

water up to 30 mL 8. proper dilution and measurement

As ICP-Q-MS (standard addition)

Ca ICP-AES (318 nm)

Cd Pb Zn

ID-ICP-MS

KRISS As Direct measurement As INAA

Ca Cd Pb Zn

microwave-assisted acid digestion Ca Cd Pb Zn

Double ID-ICP-MS

CENAM As 0.3 g sample was taken and added with 4 mL HNO3 and 0.2 mL HF, pre-digested in the microwave oven at 140°C for 45 min, samples were left to stand overnight, then samples were digested in the microwave oven . To avoid interference in the pre-reduction step, HNO3 was evaporated in the microwave oven at 80°C for 45 min until dryness. To reduce As(V) to As(III) to favor the hydride generation, 10 mL conc. HCl acid and 10 mL of a solution containing KI and ascorbic acid each at 5% w/w. samples were left

As HG-AAS (external calibration by 2 points interpolation, each calibration standard was pre-reduced following the same procedures. Arsenic hydride was generated using NaBH4 (0.2%w/w) prepared in NaOH solution (0.05%w/w)

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to stand overnight and were finally diluted with water up to 100g

Ca(1) Sample and calibrant of 0.3g and 4.8g respectively were weighed into cleaned Teflon vessel, spiked solution of Yttrium as internal standard was added gravimetically to each sample and calibrants, 10 mL HNO3 and 0.2 mL HF were added to samples and calibrants, samples and calibrants were pre-digested in the microwave oven at 140°C for 45 min, samples were digested in the microwave, then finally samples were diluted to reach the working range in the instrument.

Ca(1) High precision ICP-AES with Yttrium as internal standard, applying drift correction. The wavelength for calcium was 317.933 nm and 360.073 nm for yttrium.

Cd Pb Zn Ca(2)

0.3g sample taken into cleaned Teflon vessel, spiked mixture solution of 206Pb, 66Zn, 111Cd and 42Ca as enriched isotopes were added gravimetrically to each sample and primary materials. The isotopic ratios between the primary standards and spiked mixture were matched as close as possible. 10 mL HNO3 and 0.2 mL HF were added to samples and calibrants and pre-digested in the microwave oven at 140°C for 45 min, samples were digested in the microwave oven, finally re-dissolved in 10 mL of 7% HCl. Anion exchange separation method was used for separation of Cd, Zn and Pb. Strong base type I anion exchange resin Dowex 1-X8 in NO3- form was used. Impurities like high salt matrix, some transition elements and Ca were eluted in the first fraction, which was evaporated and redissolved in 10 mL of 2% HNO3, and then a cation exchange separation method was done for Ca separation. Strong acid cation exchange resin Dowex 50W-X8.

Cd Pb Zn

ICP-sector field-MS in low resolution mode using exact matching double isotope dilution to measure. Measured rations: Cd 111Cd/ 110Cd 111Cd/ 112Cd 111Cd/ 113Cd 111Cd/ 114Cd Pb 206Pb/204Pb 206Pb/207Pb 206Pb/208Pb Zn 66Zn/64Zn 66Zn/67Zn 66Zn/68Zn

Ca(2) Exact matching double isotope dilution ICP-MS 42Ca as an enriched isotope was used, the measurand rations were: 42Ca/43Ca 42Ca/44Ca

VNIIM All microwave acid digestion 0.1 g sample with 5 mL HNO3 and 1 mL H2O2

All ICP-MS (multi-point calibration with Y as internal standard)

HSA All 1. conc. nitric acid (5.0 mL) and hydrofluoric acid (0.2 mL) were added to 0.1 g of the herb sample or blends

2. the mixture was allowed to equilibrate for 12 hrs at room temperature and 2.0 mL hydrogen

As ICP-HRMS (standard addition) concurrently using ICP-MS to account for the possible bias in the use of different instrument for the analyses

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peroxide was then added. 3. after equilibration for another 30

min, the mixture was microwave digested to give a clear digest (power: 1200 W, ramp time: 20 min, hold time: 90 min, cool down time: 30 min.) Remark: in the absence of hydrofluoric acid, a cloudy digest containing possibly siliceous material was obtained

Ca ICP-OES (standard addition) concurrently using ICP-MS to account for the possible bias in the use of different instrument for the analyses

Cd Pb Zn

ICP-HRMS (exact matching IDMS) concurrently using ICP-MS to account for the possible bias in the use of different instrument for the analyses.

JSI (1) As Ca Cd Zn

direct measurement (230 mg pellet form)

As Ca Cd Zn

k0-INAA (Cd-ratio for multi-monitor method for determination of f and α parameters, absolute calibrated HPGe detector, IRMM-530RA Al-0.1%Au alloy, k0-standardization method of NAA)

JSI (2) All microwave acid digestion (HNO3 + H2O2)

As Cd Pb Zn

ICP-MS

Ca FAAS NIMT All microwave acid digestion

1. approximate 0.15 g of sample was accurately weighed into microwave vessel (for Ca, 42Ca spike solutions were added to give 44Ca/42Ca ratio approximately 1; for Cd, 111Cd spike solutions were added to give 112Cd/111Cd ratio approximately 1;for Pb, 206Pb spike solutions were added to give 208Pb /206Pb ratio approximately 1; for Zn, 67Zn spike solutions were added to give 66Zn/67Zn ratio approximately 1)

2. the mixture were then digested in the microwave digestion unit with 5.0 mL HNO3, 1 mL H2O2 and 1 mL HF at 1100 W for 35 min. A clear solution was obtained.

3. digested solutions were diluted to approximately 50 mL with Milli-Q water to reduce acid concentration prior to analysis.

As ICP-MS (standard addition)

Ca Cd Pb Zn

ICP-MS (IDMS)

TUBITAK UME

All microwave acid digestion using a mixture of HNO3-H2O2-HF

All HR-ICP-MS (matrix matching addition calibration)

NIST As microwave acid digestion with HNO3 and H2O2

As HR-ICP/MS (standard addition)

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Ca Cd Pb Zn

microwave acid digestion with HNO3 and HF

Ca Zn

ICP-OES (standard addition)

Cd Pb

ICPMS (isotope dilution)

LGC As 1. microwave oven digestion (0.2 g sample with 2.5 mL HNO3, 0.25 mL HF and 2.5 mL H2O2)

2. two further additions of H2O2 and re-digestion in a closed system

3. an appropriate amount of Ge was added to each vessel prior to digestion

As Q-ICP-MS with helium collision gas. On-line addition of 2% (v/v) propan-2-ol (carbon source) to the plasma to enhance 75 As signal. Standard addition using Ge as an internal standard

Remarks a. LGC mentioned that As(III) and As(V) would have different response factors by

ICP-MS as reported by NMIJ [3], and it had put considerable effort into addressing the issue during the study. Effort to address carbon enhancement effects was also made [4].

b. The same moisture determination procedure as stipulated in the previous

comparison programme CCQM-P97 was followed in this key comparison. Though some participants reported that there were difficulties encountered in the determination of the dry mass factor, the observed spread was consistent with the spread of figures obtained by the piloting laboratory.

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5. Results and Discussion 5.1 General

A total of 78 measurement results were reported for the CCQM-K89 from 18 NMIs/DIs. As stipulated in the technical protocol, participants were required to report their results on dry mass basis. For reference purposes, participants were also asked to report the dry mass correction factor in the result proforma according to the moisture determination procedure given in the technical protocol. Table 5 summarizes the dry mass correction factors reported by the participants. As noticed, three different formats of correction factor were being used by participants, viz. 1- (moisture%/100), 1/(1-(1-moisture%/100), moisture%. For ease of comparison, the presentation of dry mass correction factor was unified as 1- (moisture%/100). As observed in Figure 1, the dry mass correction factors obtained from all participants except VNIIM ranged from 0.9030 to 0.9448. The reported results of the target analytes, which were sorted by the reported values, were compiled and presented in Tables 6-10.

Table 5: Summary of moisture determination results

Institute Dry mass correction factor

as reported (1-moisture%/100) INTI 0.915 0.915 NMIA 1.0584 0.9448 BIM 1.093 0.9149 NRC 0.92957 0.92957 NIM 7.25% 0.9275 LNE 0.926 0.926 PTB 0.918 0.918 GLHK 0.9030 (As) 0.9030 (As)

0.9117 (Ca) 0.9117 (Ca) 0.9235 (Cd) 0.9235 (Cd) 0.9239 (Pb) 0.9239 (Pb) 0.9030 (Zn) 0.9030 (Zn)

NMIJ 0.9167 0.9167 KRISS 1.0826 (As) 0.9237 (As)

1.0891(Ca, Cd, Pb, Zn) 0.9182 (Ca, Cd, Pb, Zn)CENAM 0.9358 (As, Ca) 0.9358 (As, Ca)

0.9232 (Cd, Pb, Zn) 0.9232 (Cd, Pb, Zn) VNIIM 1.00 1.00 HSA 0.92 0.92 JSI 1.0947 0.9135 NIMT 8.84% 0.9116 TUBITAK UME 0.9224 0.9224 NIST 0.9285 (As) 0.9285 (As)

0.92855 (Ca, Cd, Pb, Zn) 0.92855 (Ca, Cd, Pb, Zn)LGC 0.9146 0.9146

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Figure 1: Moisture determination results

Table 6: Reported results on Arsenic

Institute Reported

value (μg/g)

Reported std.

uncertainty (μg/g)

Dry mass

factor Method

VNIIM 1.01 0.04 1.00 ICP-MS

BIM 1.08 0.13 0.9149 ICP-MS

NMIA 1.283 0.018 0.9448 ICP-SF-MS std addition

PTB 1.290 0.018 0.918 HR-ICP-MS

NIST 1.295 0.027 0.9285 HR-ICP-MS

NRC 1.30 0.05 0.92957 HG-ET-AAS

NMIJ 1.313 0.011 0.9167 ICP-MS std addition

JSI (2) 1.34 0.03 0.9135 ICP-MS

TUBITAK UME 1.35 0.06 0.9224 HR-ICP-MS

CENAM 1.359 0.038 0.9358 HG-AAS std addition

HSA 1.360 0.049 0.92 HR-ICP-MS std addition

KRISS 1.362 0.032 0.9237 INAA

NIMT 1.37 0.05 0.9116 ICP-MS std addition

LGC 1.380 0.025 0.9146 ICP-MS std addition

GLHK 1.39 0.02 0.9030 HR-ICP-MS std addition

JSI (1) 1.39 0.06 0.9135 INAA

INTI 1.43 0.07 0.915 GF-AAS std addition

NIM 1.443 0.023 0.9275 ICP-MS std addition

Dry

mas

s cor

rect

ion

fact

or

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Table 7: Reported results on Calcium

Institute

Reported

value

(mg/g)

Reported std.

uncertainty (mg/g)

Dry mass

factor Method

BIM 12.5 3.1 0.9149 ICP-MS

NRC 25.7 0.5 0.92957 ICP-OES

JSI (2) 25.7 1.1 0.9135 FAAS

VNIIM 25.9 0.6 1.00 ICP-MS


CENAM (1) 26.29 0.18 0.9358 IS-ICP-AES

JSI (1) 26.37 0.87 0.9135 INAA

NIMT 26.73 0.56 0.9116 ID-ICP-MS

NMIJ 26.76 0.25 0.9167 ICP-AES

HSA 26.760 0.39 0.92 ICP-OES std addition

CENAM (2) 26.77 0.46 0.9232 IE-ID-ICP-MS

KRISS 26.79 0.30 0.9182 ID-ICP-MS

PTB 26.860 0.105 0.918 Ion Chromatography

GLHK 27.0 0.4 0.9117 ICP-OES std addition

NIM 27.2 0.14 0.9275 ICP-OES

NIST 27.268 0.028 0.92855 ICP-OES std addition

INTI 27.4 0.4 0.915 FAAS

Table 8: Reported results on Cadmium

Institute Reported

value (μg/g)

Reported std.

uncertainty (μg/g)

Dry mass

factor Method

VNIIM 2.99 0.07 1.00 ICP-MS

BIM 3.03 0.05 0.9149 ICP-MS

JSI (2) 3.97 0.06 0.9135 ICP-MS

GLHK 4.03 0.06 0.9235 ID-HR-ICP-MS

CENAM 4.085 0.014 0.9232 IE-double-ID-ICP-MS

NIM 4.090 0.032 0.9275 double-IDMS

HSA 4.093 0.058 0.92 ID-HR-ICP-MS

NMIJ 4.111 0.022 0.9167 ID-ICP-MS

NIST 4.129 0.040 0.92855 ID-ICP-MS

KRISS 4.130 0.034 0.9182 ID-ICP-MS

NRC 4.19 0.043 0.92957 ID-ICP-MS

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LNE 4.198 0.026 0.926 ID-ICP-MS


NIMT 4.21 0.06 0.9116 ID-ICP-MS

JSI (1) 4.41 0.23 0.9135 INAA

Table 9: Reported results on Lead

Institute Reported

value (μg/g)

Reported std.

uncertainty (μg/g)

Dry mass

factor Method

VNIIM 5.95 0.18 1.00 ICP-MS

BIM 6.44 0.11 0.9149 ICP-MS


HSA 8.14 0.14 0.92 ID-HR-ICP-MS

NMIJ 8.149 0.069 0.9167 ID-ICP-MS

NIM 8.150 0.061 0.9275 double-IDMS

LNE 8.158 0.067 0.926 ID-ICP-MS

NIST 8.178 0.034 0.92855 ID-ICP-MS


NRC 8.22 0.11 0.92957 ID-ICP-MS

KRISS 8.229 0.041 0.9182 ID-ICP-MS

NIMT 8.34 0.10 0.9116 ID-ICP-MS

GLHK 8.44 0.10 0.9239 ID-HR-ICP-MS

JSI 8.78 0.29 0.9135 ICP-MS

Table 10: Reported results on Zinc

Institute Reported

value (μg/g)

Reported std.

uncertainty (μg/g)

Dry mass

factor Method

VNIIM 32.4 0.8 1.00 ICP-MS

BIM 37.3 0.5 0.9149 ICP-MS

JSI (2) 50.6 1.5 0.9135 ICP-MS


NMIJ 50.84 0.52 0.9167 ID-ICP-MS

LNE 50.91 0.4 0.926 ID-ICP-MS

HSA 51.210 0.62 0.92 ID-HR-ICP-MS

NIM 51.24 0.51 0.9275 double ID-MS

KRISS 51.63 0.24 0.9182 ID-ICP-MS

GLHK 51.8 0.9 0.9030 ID-HR-ICP-MS

NRC 51.90 0.54 0.92957 ID-ICP-MS

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NIMT 52.15 0.76 0.9116 ID-ICP-MS

NIST 52.36 0.17 0.92855 ICP-OES std addition

JSI (1) 52.7 1.4 0.9135 INAA

5.2. Traceability of calibrants used by participant

In the result proforma, participants were required to provide the information regarding the traceability of the calibrants they used in the comparison. The returns from the participants are summarized in Appendix I.

5.3. Calculation of the reference mass fraction values and associated uncertainties For discussion at the IAWG meeting on 1-2 Nov 2011 in Sydney, the piloting laboratory, GLHK, drafted and distributed the first draft of Draft A Report to participants in October 2011. The report summarized the calculated consensus values and their respective standard deviation using different location estimators including arithmetic mean, median, robust mean and mixture-model median (MM-median) with or without the suspected extreme values being included in the calculation. The suspected extreme values were identified using robust estimate of location μ) and dispersion σ) according to the CCQM Guidance Note [2], i.e. values outside σ±μ )) 2 corresponding to approximately 95% confidence [Table 11]. Table 11: Summary of extreme values testing results using robust estimates

Measurand Robust mean,

μ) Robust std

deviation, σ)σ−μ )) 2 σ+μ )) 2

As 1.341 0.062 1.216 1.466 Ca 26.54 0.650 25.24 27.84 Cd 4.106 0.116 3.874 4.338 Pb 8.148 0.254 7.639 8.657 Zn 51.33 0.95 49.42 53.23

As depicted in Tables 12 and 13, except for the case of arithmetic mean, there was good agreement amongst the calculated values when median, robust mean or MM-median was used as the location estimator with or without the suspected extreme values. (Remark: Values of MM-median and S(MM-median) were obtained as direct output of the Mixture Model Probability Density Function (MM-PDF, Version <1-May-04>) developed by Dr. David Duewer of NIST. )

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Table 12: Results of calculation of consensus values and respective standard deviation (all data included)

Measurand Arithmetic

mean

Standard

deviationMedian MADe

Robust

mean

Robust

stdev

MM-

median

S(MM-

median)

As 1.319 0.110 1.354 0.057 1.341 0.062 1.338 0.073

Ca 25.77 3.46 26.76 0.65 26.54 0.65 26.69 0.76

Cd 3.991 0.410 4.111 0.120 4.106 0.116 4.108 0.105

Pb 7.940 0.774 8.168 0.084 8.148 0.254 8.180 0.190

Zn 49.32 5.98 51.24 0.95 51.33 0.95 51.33 1.17

Table 13: Results of calculation of consensus values and respective standard

deviation (after removal of suspected extreme values)

Measurand Arithmetic

mean

Standard

deviationMedian MADe

Robust

mean

Robust

stdev

MM-

median

S(MM-

median)

As 1.353 0.048 1.360 0.045 1.352 0.052 1.350 0.066

Ca 26.60 0.54 26.76 0.60 26.60 0.60 26.74 0.68

Cd 4.142 0.107 4.129 0.092 4.133 0.082 4.123 0.084

Pb 8.231 0.227 8.179 0.059 8.213 0.121 8.200 0.146

Zn 51.54 0.68 51.63 0.77 51.53 0.76 51.51 0.98

Among others, results of Table 13 and the use of MM-median approach for the KCRV calculation were presented by the piloting laboratory at the 2011 IAWG meeting in Sydney. The IAWG meeting agreed that for participants submitted more than one result for a particular measurand, only the one with the least standard measurement uncertainty would be included in the calculation of KCRV. However, the piloting laboratory received a number of comments on the approach for the KCRV calculation afterwards. The comments pointed out that, when MM-median approach was used, uncertainty of KCRV, u(KCRV), should be calculated as the dispersion associated with the location estimator, i.e. the standard deviation of the MM-median divided by square root of n, where n is number of laboratories included in the calculation. Outliers should also be included in the calculation of KCRV and removal of outliers should be based on technical reasons rather than statistical grounds. Regarding the approach for the KCRV calculation, the comments highlighted that other approaches might be more appropriate instead of MM-median for the calculation of KCRV. It was also pointed out that not all CCQM statisticians agreed

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that MM-median is suitable for the calculation of, which is better for identifying non-normal data sets. Compared with other approaches, median is robust, simple to calculate and understand, and has a clear relationship with the data from which it was derived. Apart from comments on the KCRV calculation, the pilot laboratory also received findings from participants upon their review on the results they submitted for this comparison. Among others, VNIIM informed that the significant deviations of their results for Cd, Pb, Zn and As from KCRV were probably connected with incomplete account of matrix influences. Also, they were not able to carry out the sample analysis by IDMS method because of technical problems. BIM informed that HF was not used during sample digestion. As a result, there was un-dissolved matrix (predominantly SiO2) which might absorb part of the elements to be determined. In addition, some of their ICP-MS settings were not optimized for the specific elements' analyses. Based on their further findings, BIM agreed not to include all their results in the KCRV calculation while VNIIM agreed to exclude their results for As, Cd, Pb and Zn in the KCRV calculation. After serious consideration of all received comments, the piloting laboratory proposed using Median approach for the KCRV calculation in the IAWG meeting held in Istanbul on 9-10 October 2012. The meeting agreed to the proposal and noted that results from VNIIM and BIM that had been identified with technical problems would not be included in the KCRV calculation. In addition, as agreed in the IAWG 2011 meeting in Sydney, for participants submitted more than one result for a particular measurand, only the one with the least standard measurement uncertainty would be included in the calculation. The associated uncertainty is calculated as follows according to the CCQM Guidance Note [2]. The calculated KCRV and u(KCRV) using “Median” approach are summarized in Table 14. (3) Table 14: The KCRV and KCRU of CCQM-K89 using Median approach

Measurand KCRV u(KCRV) KCRU KCRU, %As 1.359μg/g 0.015μg/g 0.030 μg/g 2.2 Ca 26.76mg/g 0.21 mg/g 0.42 mg/g 1.6 Cd 4.12μg/g 0.028μg/g 0.056 μg/g 1.4 Pb 8.18μg/g 0.021μg/g 0.042 μg/g 0.5 Zn 51.72μg/g 0.26μg/g 0.52 μg/g 1.0

nMADe25.1)KCRV(u ⋅

=

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For ease of reference, the results of the CCQM-K89 and CCQM-P126 are presented in Figures 2-6 with the respective KCRV and u(KCRV). The red bold lines represent the KCRV (Median) and the dashed lines represent the associated standard uncertainty u(KCRV). The bar line of individual participant’s result covers reported result ± standard uncertainty. Figure 2: Arsenic measurement results and uncertainties

♦ ICP-MS HR-ICP-MS INAA ▲ AAS + ICP-OES

Note: Participants' results are displayed with error bars representing reported standard uncertainties. The solid horizontal line in red is the KCRV and the dashed lines show the standard uncertainty of the KCRV. (* result not included in the calculation of KCRV)

Mas

s fra

ctio

n of

As,

μg/g

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Figure 3: Calcium measurement results and uncertainties

♦ ICP-MS - Ion chrom. INAA + ICP-OES

HR-ICP-MS ■ ID-ICP-MS ▲ AAS


Mas

s fra

ctio

n of

Ca,

mg/

g

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Figure 4: Cadmium measurement results and uncertainties

♦ ICP-MS HR-ICP-MS INAA + ICP-OES ■ ID-ICP-MS


Mas

s fra

ctio

n of

Cd,

μg/

g

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Figure 5: Lead measurement results and uncertainties

♦ ICP-MS HR-ICP-MS + ICP-OES ■ ID-ICP-MS


Mas

s fra

ctio

n of

Pb,

μg/

g

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Figure 6: Zinc measurement results and uncertainties

♦ ICP-MS HR-ICP-MS INAA ▲ AAS + ICP-OES ■ ID-ICP-MS


Mas

s fra

ctio

n of

Zn,

μg/

g

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5.4 Equivalence statements The degree of equivalence and its uncertainty of a reported result by a participant NMI/DI compared to the KCRV are computed using Formulae 4 - 6 as follows:

)( KCRVxd ii −= (4)

KCRVKCRVxdrel i

i)(. −

= (5)

22 )()(2)( KCRVuxudU ii +⋅= (6)

where xi is the reported value from participant (i=1 to n) di is the difference between the reported value and the KCRV U(di) is the expanded uncertainty (k=2) of the difference di at a 95% level of confidence

The equivalence statements for CCQM-K89 based on the calculated KCRV using the Median approach are given in Tables 15-19 and are shown graphically in Figures 7-11 respectively.

Table 15: Equivalence statement of Arsenic for CCQM-K89

Institute Reported

value, xi, μg/g

Reported standard

uncertainty, u(xi)

Difference from KCRV U(di) di/U(di)

di rel. di

VNIIM 1.01* 0.04 -0.349 -25.7% 0.085 -4.09 BIM 1.08* 0.13 -0.279 -20.5% 0.262 -1.07

NMIA 1.283 0.018 -0.076 -5.6% 0.047 -1.63 PTB 1.290 0.018 -0.069 -5.1% 0.047 -1.48 NIST 1.295 0.027 -0.064 -4.7% 0.062 -1.04 NRC 1.30 0.05 -0.059 -4.3% 0.104 -0.57 NMIJ 1.313 0.011 -0.046 -3.4% 0.037 -1.24 JSI (2) 1.34 0.03 -0.019 -1.4% 0.067 -0.28

TUBITAK UME

1.35 0.06 -0.009 -0.7% 0.124 -0.07

CENAM 1.359 0.038 0.000 0.0% 0.082 0.00 HSA 1.360 0.049 0.001 0.1% 0.102 0.01

KRISS 1.362 0.032 0.003 0.2% 0.071 0.04 NIMT 1.37 0.05 0.011 0.8% 0.104 0.11 LGC 1.380 0.025 0.021 1.5% 0.058 0.36

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GLHK 1.39 0.02 0.031 2.3% 0.050 0.62 JSI (1) 1.39* 0.06 0.031 2.3% 0.124 0.25 INTI 1.43 0.07 0.071 5.2% 0.143 0.50 NIM 1.443 0.023 0.084 6.2% 0.055 1.53

Note: * result not included in the calculation of KCRV Table 16: Equivalence statement of Calcium for CCQM-K89

Institute Reported

value, xi, mg/g

Reported standard

uncertainty, u(xi)


di rel. di

BIM 12.5* 3.1 -14.26 -53.3% 6.214 -2.29NRC 25.7 0.5 -1.06 -4.0% 1.082 -0.98

JSI (2) 25.7* 1.1 -1.06 -4.0% 2.239 -0.47VNIIM 25.9 0.6 -0.86 -3.2% 1.269 -0.68

TUBITAK UME

26.1 0.8 -0.66 -2.5% 1.653 -0.40

CENAM (1) 26.29 0.18 -0.47 -1.8% 0.549 -0.86JSI (1) 26.37 0.87 -0.39 -1.5% 1.789 -0.22NIMT 26.73 0.56 -0.03 -0.1% 1.194 -0.03NMIJ 26.76 0.25 0.00 0.0% 0.649 0.00 HSA 26.76 0.39 0.00 0.0% 0.883 0.00

CENAM (2) 26.77* 0.46 0.01 0.0% 1.009 0.01 KRISS 26.79 0.30 0.03 0.1% 0.729 0.04 PTB 26.86 0.105 0.10 0.4% 0.464 0.22

GLHK 27 0.4 0.24 0.9% 0.901 0.27 NIM 27.2 0.14 0.44 1.6% 0.500 0.88 NIST 27.268 0.028 0.51 1.9% 0.418 1.22 INTI 27.4 0.4 0.64 2.4% 0.901 0.71

Note: * result not included in the calculation of KCRV Table 17: Equivalence statement of Cadmium for CCQM-K89

Institute Reported

value, xi, μg/g

Reported standard

uncertainty, u(xi)


di rel. di

VNIIM 2.99* 0.07 -1.130 -27.4% 0.151 -7.48BIM 3.03* 0.05 -1.090 -26.5% 0.115 -9.47

JSI (2) 3.97 0.06 -0.150 -3.6% 0.133 -1.13

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GLHK 4.03 0.06 -0.090 -2.2% 0.133 -0.68CENAM 4.085 0.014 -0.035 -0.8% 0.064 -0.55

NIM 4.09 0.032 -0.030 -0.7% 0.086 -0.35HSA 4.093 0.058 -0.027 -0.7% 0.129 -0.21NMIJ 4.111 0.022 -0.009 -0.2% 0.072 -0.12NIST 4.129 0.040 0.009 0.2% 0.098 0.09

KRISS 4.13 0.034 0.010 0.2% 0.089 0.11 NRC 4.191 0.043 0.071 1.7% 0.103 0.69 LNE 4.198 0.026 0.078 1.9% 0.077 1.01

TUBITAK UME

4.2 0.10 0.080 1.9% 0.208 0.38

NIMT 4.21 0.06 0.090 2.2% 0.133 0.68 JSI (1) 4.41* 0.23 0.290 7.0% 0.464 0.63

Note: * result not included in the calculation of KCRV Table 18: Equivalence statement of Lead for CCQM-K89

Institute Reported

value, xi, μg/g

Reported standard

uncertainty, u(xi)


di rel. di

VNIIM 5.95* 0.18 -2.229 -27.3% 0.363 -6.15BIM 6.44* 0.11 -1.739 -21.3% 0.224 -7.76

CENAM 7.81 0.17 -0.369 -4.5% 0.343 -1.08HSA 8.14 0.14 -0.039 -0.5% 0.283 -0.14NMIJ 8.149 0.069 -0.030 -0.4% 0.144 -0.21NIM 8.15 0.061 -0.029 -0.4% 0.129 -0.22LNE 8.158 0.067 -0.021 -0.3% 0.141 -0.15NIST 8.178 0.034 -0.001 0.0% 0.080 -0.01

TUBITAK UME

8.18 0.20 0.001 0.0% 0.402 0.00

NRC 8.22 0.11 0.041 0.5% 0.224 0.18 KRISS 8.229 0.041 0.050 0.6% 0.092 0.54 NIMT 8.34 0.10 0.161 2.0% 0.204 0.79 GLHK 8.44 0.10 0.261 3.2% 0.204 1.28

JSI 8.78 0.29 0.601 7.3% 0.582 1.03 Note: * result not included in the calculation of KCRV

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Table 19: Equivalence statement of Zinc for CCQM-K89

Institute Reported

value, xi, μg/g

Reported standard

uncertainty, u(xi)


di rel. di

VNIIM 32.4* 0.8 -19.315 -37.4% 1.685 -11.47BIM 37.3* 0.5 -14.415 -27.9% 1.130 -12.75

JSI (2) 50.6* 1.5 -1.115 -2.2% 3.046 -0.37CENAM 50.69 0.65 -1.025 -2.0% 1.403 -0.73

NMIJ 50.84 0.52 -0.875 -1.7% 1.166 -0.75LNE 50.91 0.4 -0.805 -1.6% 0.958 -0.84HSA 51.21 0.62 -0.505 -1.0% 1.347 -0.37NIM 51.24 0.51 -0.475 -0.9% 1.148 -0.41

KRISS 51.63 0.24 -0.085 -0.2% 0.713 -0.12GLHK 51.8 0.9 0.085 0.2% 1.876 0.05 NRC 51.9 0.54 0.185 0.3% 1.202 0.15

TUBITAK UME

52 1.4 0.285 0.5% 2.849 0.10

NIMT 52.15 0.76 0.435 0.8% 1.609 0.27 NIST 52.36 0.17 0.645 1.2% 0.627 1.03 JSI (1) 52.7 1.4 0.985 1.9% 2.849 0.35

Note: * result not included in the calculation of KCRV Figure 7: Equivalence statement of As, in terms of rel. Di, for CCQM-K89. Points are plotted with the associated expanded uncertainty in the degree of equivalence corresponding to an approximately 95% coverage range.

Note: * result not included in the calculation of KCRV

rel.

Di f

or A

s

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Figure 8: Equivalence statement of Ca, in terms of rel. Di, for CCQM-K89. Points are plotted with the associated expanded uncertainty in the degree of equivalence corresponding to an approximately 95% coverage range.


Figure 9: Equivalence statement of Cd, in terms of rel. Di, for CCQM-K89. Points are plotted with the associated expanded uncertainty in the degree of equivalence corresponding to an approximately 95% coverage range.


rel.

Di f

or C

a

rel.

Di f

or C

d

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Figure 10: Equivalence statement of Pb, in terms of rel. Di, for CCQM-K89. Points are plotted with the associated expanded uncertainty in the degree of equivalence corresponding to an approximately 95% coverage range.


Figure 11: Equivalence statement of Zn, in terms of rel. Di, for CCQM-K89. Points are plotted with the associated expanded uncertainty in the degree of equivalence corresponding to an approximately 95% coverage range.


rel.

Di f

or P

b re

l. D

i for

Zn

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6. Demonstration of Core Capabilities As agreed in previous IAWG meetings, a system of Core-Capabilities for inorganic analysis will be employed in key comparisons starting from CCQM-K75 onward. This strategy is to improve the efficiency and effectiveness of key comparisons to support CMC claims. With the use of this system, new CMC claims can be supported by describing which Core-Capabilities are required to provide the claimed measurement service and then referencing Core-Capabilities that were successfully demonstrated by participation in key comparisons. In this connection, 16 participants submitted their Core-Capabilities (CCs) Tables to the organizer for compilation. In the meeting on 1-2 November 2011, IAWG briefly discussed the input on core capabilities from participants. To facilitate further discussion, the returns from participants were consolidated according to 6 different analytical techniques, namely AAS, ICP-AES, ICP-MS (without isotope dilution), ICP-MS (with isotope dilution), INAA and ion chromatography respectively and are given in the Appendix II. For ease of reference, the revised template with changes in the column headings was used in the presentation.

7. Conclusion With respect to the methodology, except those participants using INAA as the measurement technique, most of the participants used microwave acid digestion methods for sample treatment. However, for the determination of arsenic, though the results were not statistically different, technically it seemed appropriate to recommend using HF in this type of complex matrix since the participants who did not use HF reported consistently slightly lower values. For the instrumental determination, a variety of techniques like ICP-MS, AAS, INAA, ICP-AES were employed by the participants. Compared with CCQM-K89, a wider dispersion among the results of the participants in CCQM-P126 was noted for all measurands. This may imply that there is still room for improvement for some of the participants of the pilot study.

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ACKNOWLEDGEMENT The contract persons, analysts and NMIs/DIs responded to this study and contributed their efforts to the CCQM-K89 key comparison, as listed below, are highly appreciated and acknowledged.

Institute Contact person and/or analysts

INTI Liliana Valiente NMIA David Saxby, Jeffrey Merrick INMETRO Rodrigo Caciano de Sena BIM Boriana Kotzeva NRC Zoltan Mester, Lu Yang, Scott Willie NIM Liuxing Feng, Jun Wang LNE Guillaume Labarraque PTB Olaf Rienitz

GLHK Della Wai-mei Sin, Chuen-sing Mok, Siu-kay Wong, Chi-shing Ng, Wai-hong Fung, Ho-pan Yau

INRiM Luifi Bergamaschi NMIJ Yanbei Zhu KRISS Yong-Hyeon Yim, Kyoung Seok Lee, In Jung Kim, Young Ran Lim

CENAM Pedro Ramirez Cruz, Flora E. Mercader Trejo, Edith Valle Moya, Itzel Santiago Castellanos, Maria del Rocio Arvizu Torres, Judith Velina Lara Manzano

VNIIM L.A. Konopelko, Yu A. Kustikov HSA Richard Shin JSI Milena Horvat, Radojko Jacimovic, Radmila Milacic

NIMT Charun Yafa, Sutthinun Taebunpakul, Nattikarn Kaewkhomdee, Pranee Phukphatthanachai

TUBITAK UME Oktay Cankur, F. Gonca Coskun NIST Gregory C. Turk, W. Clay Davis, Laura J. Wood, Karen E. Murphy LGC John Entwisle

The piloting laboratory would like to thank Dr. M. Sargent, the Chairman of the IAWG/CCQM for his encourage and guidance through the study. References 1. International Standards Organization, ISO Guide 35: Reference materials – General

and statistical principles for certification, Geneva, Switzerland, 2006. 2. CCQM Guidance note: Estimation of a consensus KCRV and associated degrees of

equivalence, Version 6, 2010. 3. Differences in sensitivity between As(III) and As(V) measured by inductively coupled

plasma spectrometry and the factors affecting the incoherent molecular formation (IMF) effect in the plasma, by Tomohiro Narukawa, Koichi Chiba, Takayoshi Kuroiwa and Kazumi Inagaki, J. Anal. At. Spectrom., 2010, 25, 1682-1687.

4. Development of an accurate procedure for the determination of arsenic in fish tissue of marine origin by ICP-MS by John Entwisle, Ruth Hearn, Spectrochimica Acta, Part B 61 (2006) 438-443.

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Appendix I

Participant Traceability of calibrants used by participants

As Ca Cd Pb Zn

BIM MERCK (CertiPur)

CENAM CENAM CRM DMR-312b SMU CRM SMU-B07 CENAM CRM DMR461a NIST SRM 981 CENAM CRM DMR441a

GLHK NIST SRM 3103a NIST SRM 3109a NIST SRM 3108 NIST SRM 3128 NIST SRM 3168a

HSA NIST SRM 3103a NIST SRM 3109a NIST SRM 3108 NIST SRM 3128 NIST SRM 3168a

INTI NIST SRM 3103a NIST SRM 3109a N.A.

JSI (a) k0-INAA: Cd-ratio for multi monitor method for determination of f and α parameters, absolute calibrated HPGe detector, IRMM-530RA Al-0.1%Au alloy, k0-standardization method of NAA (b) ICP-MS: Simultaneous determination from prepared multi-standards (NIST single standards).

KRISS KRISS primary standard solutions

LGC Traceability to NIST SRM 3103a with the use of Puratronic Arsenic (III) oxide 99.996% pure by Alfa Aesar, Lancashire, UK

N.A.

LNE N.A. high purity standards obtained from Prolabo were further characterized by LNE with support of respective CMC claims

NIST SRM 682

NIM GBW08611 GBW(E)080118 GBW08612,

GBW04441

GBW08619,

GBW04442

GBW08620

NIMT NIST SRM 3103a NIST SRM 3109a NIST SRM 3108 NIST SRM 3128 NIST SRM 3168a

NIST NIST SRM 3103a NIST SRM 3109a NIST SRM 3108 NIST SRM 3128 NIST SRM 3168a

NMIA NIST SRM 3103a N.A.

NMIJ Traceable to SI through JCSS system

NRC N.A. Traceable to the SI through use of gravimetrically prepared standards of established purity held at the NRC

PTB As standard solution, prepared from HPS As, was verified by comparing it to NIST SRM 3103a (Arsenic Standard Solution), to Merck CertPUR Arsenic standard solution (traceable to NIST, 119773) and to a standard solution prepared by PTB from a candidate primary material provided by BAM.

NIST SRM 915b N.A.

TUBITAK

UME

NIST SRM 3103a NIST SRM 3109a NIST SRM 3108 NIST SRM 3128 NIST SRM 3168a

VNIIM Commercial source, in-house purity assessment using ICP-MS techniques with competence demonstrated by CMCs & participation in

CCQM comparisons

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Appendix II Inorganic Core Capabilities

Summary Table CCQM Study: CCQM-K89 Trace & Essential Elements in Herba Ecliptae Institute: CENAM, INTI, NRC Method: AAS (CENAM:HG-AAS, NRC:HG-GF-AAS, INTI:GF-AAS(As);

FAAS(Ca)) Analytes: CENAM, INTI – As INTI – As, Ca

Capabilities/Challenges Not tested Tested Specific challenges encountered

Contamination control and correction All techniques and procedures employed to reduce potential contamination of samples as well as blank correction procedures. The level of difficulty is greatest for analytes that are environmentally ubiquitous and also present at very low concentrations in the sample.

NRC, INTI, CENAM

Digestion/dissolution of organic matrices All techniques and procedures used to bring a sample that is primarily organic in nature into solution suitable for liquid sample introduction to the ETA-AAS.

NRC, INTI, CENAM

Pre-digestion procedure was applied to avoid high pressure in the vessels due the biological sample (CENAM).

Digestion/dissolution of inorganic matrices All techniques and procedures used to bring a sample that is primarily inorganic in nature into solution suitable for liquid sample introduction to the ETA-AAS.

NRC, INTI, CENAM

Sample contains SiO2 (INTI). Sample digestion require HF for complete dissolution of silicon (CENAM)

Volatile element containment All techniques and procedures used to prevent the loss of potentially volatile analyte elements during sample treatment and storage.

NRC, INTI, CENAM

As is a highly volatile element. Closed vessel sample digestion is needed to prevent As losses (CENAM) Digestion using closed vessel (INTI)

Pre-concentration Techniques and procedures used to increase the concentration of the analyte introduced to the ETA-AAS. Includes evaporation, ion-exchange, extraction, precipitation procedures, but not vapor generation procedures.

CENAM NRC, INTI Pd + Mg modifier fir trapping of volatiles in GF (INTI)

Matrix separation CENAM, NRC

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Techniques and procedures used to isolate the analyte(s) from the sample matrix to avoid or reduce interferences caused by the matrix. Includes ion-exchange, extraction, precipitation procedures, but not vapor generation procedures.

INTI

Hydride preconcentration/matrix separation of volatile species. Coupling of a hydride system to the ETA-AAS and optimization of conditions.

INTI NRC, CENAM

Digestion of samples with HNO3 converts arsenic into the higher oxidation state (As V), which results in low hydride generation efficiency. As (V) must be pre-reduced to As (III) in order to favor de hydride formation. HNOs must be evaporated to avoid interference before adding KI as reducing agent (CENAM)

Atomization (flame/Graphite furnace) NRC, CENAM

INTI

Stabilization of samples and standards NRC, CENAM

INTI

Calibration of analyte concentration The preparation of calibration standards and the strategy for instrument calibration. Includes external calibration and standard additions procedures. Also use of matrix-matched standards to minimize effect of interferences.

NRC, INTI, CENAM

Signal detection The detection and recording of the absorption signals of analytes. The degree of difficulty increases for analytes present at low concentrations, of low atomic absorption coefficient. Requires selection of operating conditions such as light source, absorption line, Zeeman background correction conditions. Includes selection of signal processing conditions (peak area or height).

NRC, INTI, CENAM

Linear range NRC, CENAM

INTI

correction or removal of matrix-induced signal suppression or enhancement

NRC, INTI, CENAM

Acids used for sample digestion (HNO3 and HF) are sources of interferences. They must be evaporated to avoid interferences. Due to the volatility of arsenic, temperature of evaporation must be carefully selected to avoid losses of arsenic during evaporation stage (CENAM) Interferences in the absorbance signal in samples with high nitric acid concentration. Evaporation after MW digestion was necessary. For Ca, N2O:C2H2 flame and La were used as suppressor of interference (INTI)

Selection of matrix modifier NRC, CENAM

INTI

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Matching of the standards and sample matrix

NRC, CENAM

INTI Standard addition calibration (INTI)

Memory effect Any techniques used to avoid, remove or reduce the carry-over of analyte between consecutively measured standards and/or samples.

INTI,

NRC, CENAM

In order to avoid the memory effect, it was used the bracketing method (CENAM)

Optimization of the furnace temperature program Optimization of temperature and duration of steps for sample drying, pyrolysis to remove (residual) organics, and atomization. Furnace temperature program to minimize analyte loss in the drying/pyrolysis steps, while maximizing analyte vaporization in the atomization step.

INTI, CENAM

NRC

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Inorganic Core Capabilities Summary Table

CCQM Study: CCQM-K89 Trace & Essential Elements in Herba Ecliptae Institute: NMIJ, NIST, HSA, CENAM, GLHK, NRC Method: ICP-AES Analytes: NMIJ, HSA, CENAM, GLHK, NRC - Ca NIST – Ca, Zn



NMIJ, NIST, HSA, GLHK, NRC, CENAM

Digestion/dissolution of organic matrices All techniques and procedures used to bring a sample that is primarily organic in nature into solution suitable for liquid sample introduction to the ICP.


Pre-digestion procedure was applied to avoid high pressure in the vessels due the biological sample (CENAM).

Digestion/dissolution of inorganic matrices All techniques and procedures used to bring a sample that is primarily inorganic in nature into solution suitable for liquid sample introduction to the ICP.

NIST NMIJ, GLHK, NRC, HAS, CENAM

Sample digestion requires HF acid for complete dissolution due to the presence of siliceous material (HAS, CENAM)


NIST, GLHK, CENAM

NMIJ, HSA, NRC

Pre-concentration Techniques and procedures used to increase the concentration of the analyte introduced to the ICP. Includes evaporation, ion-exchange, extraction, precipitation procedures, but not vapor generation procedures.

NIST, HSA, GLHK, NRC, CENAM

NMIJ

Vapor generation Techniques such as hydride generation and cold vapor generation used to remove the analyte from the sample as a gas for introduction into the ICP.

NIST, HSA, GLHK, NRC, CENAM

NMIJ

Matrix separation NIST, NMIJ

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Techniques and procedures used to isolate the analyte(s) from the sample matrix to avoid or reduce interferences caused by the matrix. Includes ion-exchange, extraction, precipitation procedures, but not vapor generation procedures. Techniques and procedures used to isolate the analyte(s) from the sample matrix to avoid or reduce interferences caused by the matrix. Includes ion-exchange, extraction, precipitation procedures, but not vapor generation procedures.

HSA, GLHK, NRC, CENAM

Calibration of analyte concentration The preparation of calibration standards and the strategy for instrument calibration. Includes external calibration and standard additions procedures.

NIST NMIJ, HSA, GLHK. NRC, CENAM

Line selection for the analyte and internal standard must be similar in properties to match the physical and chemical characteristics. Care must be taken to avoid spectral interference from unknown’s sources in both analyte and internal standard. The use of high precision internal standardization method required the selection of the best match ratio, which is an issue, in order to minimize the error (CENAM) Direct (NRC)

Signal detection The detection and recording of the analyte signals. The degree of difficulty increases for analytes present at low concentrations, or that are have weak emission lines..



NMIJ, HSA, GLHK, NRC, CENAM

NIST

Complex spectral backgrounds/ correction of spectral interference Any techniques used to remove, reduce, or mathematically correct for interferences caused by the overlap of analyte emission lines with atomic, ionic, or molecular emission from matrix components. The relative concentrations and sensitivities of the analyte and the interfering species will affect the degree of difficulty. Samples containing high concentration matrix components with large numbers of emission lines or molecular bands may increase the measurement challenge.


Sample and spectra of single-element solutions of the analyte and internal standard were measured in the same spectral region to determine the cross-contamination or spectral overlaps occur. The calcium content is relatively high, although some wavelength of internal standard present unknown interference which could affects the

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value of the ratio measured. This must be corrected properly (CENAM)

Correction or removal of matrix-induced signal suppression or enhancement Chemical or instrumental procedures used to avoid or correct for matrix-induced signal suppression or enhancement. High concentrations of acids, dissolved solids, or easily ionized elements will increase the degree of difficulty.

CENAM NMIJ, NIST, HSA, GLHK, NRC

Use of standard addition (GLHK)

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CCQM Study: CCQM-K89 Trace & Essential Elements in Herba Ecliptae Institute: NMIJ, NIST, LGC, HSA, GLHK, VNIIM, PTB, JSI, NIMT, TUBITAK

UME, NMIA Method: ICP-MS (without isotope dilution) Analytes: NMIJ, NIST, LGC, HSA, GLHK, PTB, NIMT, NMIA – As

TUBITAK UME, VNIIM, JSI – As, Ca, Cd, Pb, Zn



NMIA NMIJ, NIST, LGC, HSA, GLHK, JSI, NIMT, TUBITAK UME, PTB, VNIIM

All unknown samples and controls were processed and handled under class 100 HEPA workstations; All sample handling vessels, jars, and spatulas were pre-cleaned with 5 % UHP nitric acid in Milli-Q water; All samples and controls were digested with UHP nitric acid and UHP peroxide and diluted with Milli-Q water. (NIST)Blanks below limit of quantification (JSI)


NMIJ, NIST, LGC, HSA, GLHK, JSI, NIMT, TUBITAK UME, PTB, VNIIM, NMIA

All unknown samples and controls were microwave digestion using a standard closed vessel high temperature and pressure method. (NIST) high temperature (250 °C) necessary to decompose As-organic compounds (PTB). For the biological sample pre-digestion procedure is needed to avoid high pressure in the vessels (VNIIM) The matrix was completely decomposed (JSI) HF digestion may be required for silicates in the matrix (NMIA)

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Digestion/dissolution of inorganic matrices All techniques and procedures used to bring a sample that is primarily inorganic in nature into solution suitable for liquid sample introduction to the ICP.

NIST, NIMT, VNIIM, NMIA

NMIJ, GLHK, JSI, TUBITAK UME, PTB, LGC, HSA

hydrofluoric acid necessary to get clear solutions (PTB) Hydrofluoric acid is required in order to fully dissolve silica (LGC) Sample digestion requires HF acid for complete dissolution due to the presence of siliceous material (HSA). The matrix was completely decomposed (JSI)


LGC, GLHK, PTB,

NMIJ, NIST, HSA, JSI, NIMT, TUBITAK UME, VNIIM, NMIA

Closed vessel digestion was utilized to prevent loss of As during sample preparation. (NIST) As is a highly volatile element, therefore closed vessel sample digestion is needed to prevent As losses.(VNIIM) By the digestion procedure applied no volatility problems were observed, closed vessel MW digestion (JSI) As is volatile; closed digestion means this will not be highly problematic (NMIA)


NIST, LGC, HSA, GLHK, JSI, NIMT, TUBITAK UME, PTB, VNIIM, NMIA

NMIJ

Cold-vapor or hydride generation Techniques such as hydride generation and cold vapor generation used to remove the analyte from the sample as a gas for introduction into the ICP.

NIST, LGC, HSA, GLHK, JSI, NIMT, TUBITAK UME, PTB, VNIIM, NMIA

NMIJ

Matrix separation Techniques and procedures used to isolate the analyte(s) from the sample matrix to avoid or reduce interferences caused by the matrix. Includes ion-exchange, extraction,

NIST, LGC, HSA, GLHK, JSI, NIMT,

NMIJ

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precipitation procedures, but not vapor generation procedures. Techniques and procedures used to isolate the analyte(s) from the sample matrix to avoid or reduce interferences caused by the matrix. Includes ion-exchange, extraction, precipitation procedures, but not vapor generation procedures.

TUBITAK UME, PTB, VNIIM, NMIA

Liquid chromatographic separation NIST, HSA, GLHK, JSI, NIMT, TUBITAK UME, PTB, VNIIM, NMIA

NMIJ, LGC

Required to evaluate the oxidation state of As in standard solutions and sample digests. Also used as a confirmatory technique (LGC).

Dry mass correction NMIJ, NIST, HSA, GLHK, JSI, NIMT, TUBITAK UME, VNIIM, NMIA

PTB, LGC Long time (30 d) needed to reach stable masses using the recommended drying reagent (PTB)

Calibration of analyte concentration The preparation of calibration standards and the strategy for instrument calibration. Includes external calibration and standard additions procedures.

NIST, NIMT

NMIJ, HSA, GLHK, VNIIM, TUBITAK UME, JSI, PTB, LGC,NMIA

mono-isotopic, more efforts needed to get sufficient recoveries (PTB)Gravimetric standard addition technique at four spike levels and internal standardization was employed (LGC). Simultaneous determination from prepared multi-standards (JSI) standard addition used (ID is not possible) (NMIA)

Signal detection The detection and recording of the analyte isotope signals. The degree of difficulty increases for analytes present at low concentrations, of low isotopic abundance, or that are poorly ionized.

NMIJ, NIST, GLHK, JSI, VNIIM, NIMT, TUBITAK UME, PTB, LGC, HAS, NMIA

Traceability to the mole for total arsenic was achieved by gravimetric preparations of SRM 3103a (lot # 10018) with a certified mass fraction of 9.999 ± 0.015 mg/g; Standard addition quantification was utilized for the determination of As in the unknown sample. (NIST) internal standard necessary (PTB) High levels of dissolved solids (silica) cause a

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suppression of the 75As signal intensity during ICP-MS analysis. The use of germanium as an internal standard compensated for the signal drop (lower than 5% over 10 working hours). Increased dilution of the digests was used to minimize the solid load to the ICP but decreased signal intensity. This was compensated by addition of carbon to the plasma, which has been shown to enhance the sensitivity of 75As (LGC). At high resolution (R = 10000), the signal intensity was relatively weak (1000 cps) (HSA). As at reasonably low level (NMIA)


NMIJ, LGC, HSA, GLHK, JSI, NIMT, TUBITAK UME, PTB, VNIIM, NMIA

NIST As is mono isotopic with an 1st ionization potential of 9.81 eV but at a sufficiently high mass fraction level to be analyzed. (NIST)

Correction or removal of isobaric/polyatomic interferences Any techniques used to remove, reduce, or mathematically correct for interferences caused by mass overlap of analyte isotopes with isobaric or polyatomic species. Includes collision cell techniques, high resolution mass spectrometry, or chemical separations. The relative concentrations and sensitivities of the analyte isotopes and the interfering species will affect the degree of difficulty.

NIMT NMIJ, PTB, HSA, VNIIM, JSI, TUBITAK UME, NIST, LGC, GLHK, NMIA

As suffers from several possible polyatomic interferences most notably 40Ar35Cl therefore high resolution ICP-MS (R=10,000) was used to eliminate any potential polyatomic interferences. (NIST) chloride removed by evaporating to dryness after digestion with nitric acid (PTB). The use of helium collision cell technology effectively removes Ar-Cl interference. However, a significant reduction of signal intensity is incurred, compensated by the addition of carbon which enhances the As signal by charged transfer effect

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(LGC). High resolution mass spectrometry was used to resolve the interferences (HSA). Use of HRMS (GLHK) Polyatomic interferences were taken into account by the use of the instrument software (VNIIM) Use of the HMI and collision/reaction cell (JSI)argon based polyatomics are highly problematic, requiring accurate setup of reaction cell or high mass resolution ICPMS (NMIA)

Correction or removal of matrix-induced signal suppression or enhancement Chemical or instrumental procedures used to avoid or correct for matrix-induced signal suppression or enhancement.

NIST, HSA, JSI, NIMT, TUBITAK UME,

PTB, GLHK, NMIJ, LGC, VNIIM, NMIA

Matrix matching or standard addition is necessary for As measurement (NMIJ) It has been reported that As (V) is more sensitive than As (III) when measured by ICP-MS. Therefore, efforts are required to ensure both sample digests and standards contain As in the same oxidation state i.e. As (V). Residual carbon from digestion can cause significant enhancement of the As signal by charged transfer effect. Overcome by saturating the plasma continuously with carbon during the analysis (LGC) It is known that As (V) is more sensitive than As (III) when measured by ICP-MS. Therefore, efforts are required to ensure both sample digests and standards contain As in the same oxidation state i.e. As (V). Residual carbon from digestion can cause significant enhancement of the As signal by charged transfer effect. Overcome by saturating the plasma continuously with carbon during the analysis (VNIIM) analysis by standard addition to negate matrix

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effects (NMIA) Detector deadtime correction Measurement of, and correction for, ion detector deadtime. Importance increases in situations where high ion count rates are encountered

NIST, LGC, TUBITAK UME, VNIIM

NMIJ, PTB, HSA, GLHK, JSI, NIMT, NMIA

Agilent ICP-MS7700X: negligible (JSI) dead time correction required for accurate isotope ratio measurement. ratio-matching not possible (NMIA)

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CCQM Study: CCQM-K89 Trace & Essential Elements in Herba Ecliptae Institute: KRISS, CENAM, NMIJ, NIST, HSA, GLHK, NRC, LNE, NIMT Method: IDMS (ICP-MS) Analytes: NMIJ, HSA, GLHK, NRC, LNE – Cd, Zn, Pb KRISS, CENAM, NIMT – Ca, Cd, Pb, Zn

NIST – Cd, Pb



NMIJ, LNE, KRISS, HSA, GLHK, NRC, NIST, NIMT, CENAM

Laborious procedure employed (the water was purified by double subdistillation) to reduce potential contamination of samples as well as blank correction procedures. The level of difficulty is greatest for analytes that are environmentally ubiquitous (CENAM).


NMIJ, LNE, KRISS, HSA, GLHK, NRC, NIST, NIMT, CENAM

Microwave digestion procedure used to bring the biological sample that is primarily organic in nature into solution suitable for liquid sample introduction to the ICP (CENAM).

Digestion/dissolution of inorganic matricesAll techniques and procedures used to bring a sample that is primarily inorganic in nature into solution suitable for liquid sample introduction to the ICP.

NIMT NMIJ, GLHK, NRC, NIST, KRISS, HSA, LNE, CENAM

For complete dissolution of inorganic matrices, HF should be used for digestion. HF removal process or HF compatible ICPMS interface is required (KRISS) Sample digestion requires HF acid for complete dissolution due to the presence of siliceous material (HAS, CENAM). Adding of a few HF acid to complete the dissolution of sample (LNE)

Volatile element containment LNE, GLHK, NMIJ, NIST,

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All techniques and procedures used to prevent the loss of potentially volatile analyte elements during sample treatment and storage.

NRC, CENAM

KRISS, HSA, NIMT


LNE, KRISS, HSA, GLHK, NRC, NIST, NIMT, CENAM

NMIJ

Vapor generation Techniques such as hydride generation and cold vapor generation used to remove the analyte from the sample as a gas for introduction into the ICP.

LNE, KRISS, HSA, GLHK, NRC, NIST, NIMT, CENAM

NMIJ

Matrix separation Techniques and procedures used to isolate the analyte(s) from the sample matrix to avoid or reduce interferences caused by the matrix. Includes ion-exchange, extraction, precipitation procedures, but not vapor generation procedures. Techniques and procedures used to isolate the analyte(s) from the sample matrix to avoid or reduce interferences caused by the matrix. Includes ion-exchange, extraction, precipitation procedures, but not vapor generation procedures.

LNE, KRISS, HSA, GLHK, NRC, NIST, NIMT,

NMIJ, CENAM

Laborious Ion-exchange procedure used to isolate the analytes from the sample matrix to avoid or reduce interferences caused by the matrix (CENAM).

Spike equilibration with sample The mixing and equilibration of the enriched isotopic spike with the sample.

NIST NMIJ, NRC, KRISS, HSA, GLHK, LNE, NIMT, CENAM

Signal detection The detection and recording of the analyte isotope signals. The degree of difficulty increases for analytes present at low concentrations, of low isotopic abundance, or that are poorly ionized.

NMIJ, NRC, KRISS, HSA, GLHK, LNE, NIST, NIMT, CENAM

Correction or removal of isobaric/polyatomic interferences Any techniques used to remove, reduce, or mathematically correct for interferences caused by mass overlap of analyte isotopes with isobaric or polyatomic species. Includes collision cell techniques, high resolution mass spectrometry, or chemical separations. The relative concentrations and sensitivities of the analyte isotopes and the interfering species will affect the degree of difficulty.

Ca: NMIJ, LNE, GLHK, NRC, NIST, CENAM Zn: NRC, NIST, NIMT, CENAM

Pb & Cd: KRISS, HSA, GLHK, NRC, CENAM, NIMT, NMIJ, NIST, LNE Ca: KRISS, NIMT Zn: KRISS, HSA, NMIJ, GLHK, LNE

Interference-free isotope of Zn was not available. Separation of Cd from Mo is preferred prior to the measurement (NMIJ). 114Cd/95Mo ≈ 2:1, 114Cd/91Zr ≈ 5:1, 114Cd/118Sn ≈ 8:1. Potential Mo and Zr oxide/hydroxide interferences on 111Cd, 112Cd, 113Cd, and 114Cd reduced by use of desolvating nebulizer (Aridus). Isobaric interference from 112Sn and 114 Sn required small correction (< 1 %) (NIST)

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Interferences from polyatomic species were avoided using higher mass resolution (KRISS) Reaction cell is needed to remove polyatomic interferences on 42Ca as spike ion (NIMT) Use of HRMS (GLHK) Zn in medium resolution(NRC) Ba 2+/ Zn+ : matrix matching ZrO+- MoO+ / Cd+ : matrix matching (LNE) Mathematical correction for: 112Sn caused by mass overlap of 112Cd, 114Sn caused by mass overlap of 114Cd isobaric interference (CENAM).

correction or removal of matrix-induced signal suppression or enhancement

NIST NMIJ, NRC, KRISS, HSA, NIMT, CENAM, GLHK, LNE

IDMS (GLHK) Matrix matching (LNE)

Detector deadtime correction Measurement of, and correction for, ion detector deadtime. Importance increases in situations where high ion count rates are encountered.

NMIJ, NRC, KRISS, HSA, GLHK, LNE, NIMT, NIST, CENAM

Pb and Cd analyzed in separate dilutions, keeping count rate of major isotope less than 400,000 cps (NIST)

Mass bias/fractionation control and correction Techniques used to determine, monitor, and correct for mass bias/fractionation.

NMIJ, NRC, KRISS, HSA, GLHK, LNE, NIST, NIMT, CENAM (Pb)

For lead, the mass bias was corrected (CENAM)

Spike calibration Techniques used to determine the analyte concentration in the enriched isotopic spike solution.

HSA, CENAM

NMIJ, NIST, NIMT, GLHK, NRC, KRISS, LNE

Not required for “Exact Matching” IDMS (HSA, CENAM) Availability of high purity standards to calibrate spikes during double IDMS (LNE).

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CCQM Study: CCQM-K89 Trace & Essential Elements in Herba Ecliptae Institute: KRISS, JSI Method: Instrumental Neutron Activation Analysis (INAA) Analytes: KRISS - As

JSI – As, Ca, Cd, Zn


Sample preparation Procedures used to prepare samples for irradiation; determination of the mass basis (e.g., determination of dry mass basis); procedures to minimize sample loss during preparation; procedures to minimize contamination with the elements of interest (highest difficulty for determination of low levels of elements that are ubiquitous in the sample preparation environment).

KRISS, JSI

Aliquots of about 0.23 g of Herba Ecliptae were pelletized using a manual hydraulic press in diameter 10 mm and 2.5 mm high (JSI)

Standards preparation Procedures used to prepare element standards or other comparators used for standardization. (e.g., low difficulty for use of pure elements or compounds; higher difficulty for procedures involving dissolution and dilution, or dilution with solid matrices.)

KRISS, JSI

IRMM-530RA Al-0.1% Au alloy in form of foil with thickness of 0.1 mm was used. Discs of about 6 mm diameter were prepared (JSI)

General applications Procedures associated with specific method of NAA and the evaluation of the associated uncertainties for comparator NAA, k0 NAA, or other method specific parameters not described below.

KRISS JSI Definition is not clear (KRISS) Characterization of irradiation channel in the carousel facility (CF) of TRIGA reactor and absolute calibration of the HPGe detector are needed. Optimization and validation of the k0-INAA with different matrix certified reference materials are necessary. Concentration levels in the sample for As, Ca, Cd and Zn have to be suitable for INAA (JSI)

Determination of peak areas (complex spectra/small peaks) Procedures used to determine peak areas. (e.g., high difficulty for small peak areas on complex backgrounds or determination of areas for multiple unresolved peaks.)

KRISSJSI

Net count of the peak of the primary gamma-ray energy (559 keV) was small (<15000) but not so bad for qualification (KRISS). Negligible background spectrum corrections were used in this study (subtraction of recent background spectrum for all gamma spectra was applied) (JSI)

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Correction for spectral interferences Procedures used to determine peak areas from interfering nuclides and subtraction of the appropriate number of counts from the peak of interest. Level of difficulty increases with the number of corrections needed and the magnitude of the corrections relative to the total peak area.

KRISS, JSI

No gamma-ray peak from the elements which might cause spectral interference with 559 keV of As-76 was found (KRISS). HPGe detector with 45% relative efficiency connected to an EG&G ORTEC Spectrum Master high-rate multi-channel analyzer (zero-dead time (ZDT) mode). Negligible corrections for gamma-ray interferences were applied: 1. Cd/In-115m at 336.6 keV from Sb/Sb-124 at 336.2 keV; 2. Zn/Zn-65 at 1115.5 keV from Tb/Tb-160 at 1115.1 keV (JSI)

correction of fast neutron and fission interferences Procedures used to determine the contributions from fast neutron reactions or fission of U to the peak area of interest. The level of difficulty is related to the magnitude of the corrections needed.

KRISS, JSI

The irradiation facility is well thermalized. Fission interference does not cause any problem for As analysis (KRISS). Used irradiation channel in the CF of TRIGA reactor (IC-40) has a thermal-to-epithermal flux ratio of 28.6 and a thermal-to-fast flux ration of 7.8, For studied radionuclides (As-76, Ca-47, In-115m and Zn-65) the threshold reactions are negligible (JSI)

correction for sample/standard geometry differences Procedures used to determine correction factors for differences in sample and standard irradiation and counting geometries. These may include, e.g., use of flux monitors to determine irradiation geometry correction factors, and calculated correction factors based on measured thicknesses and sample-to-detector distances. Level of difficulty increases with the magnitude of the correction.

KRISS, JSI

Differences in sample/standard geometry are taken into account and they are taken into account and they are calculated by Kayzero for Windows (KayWin®) software, which was used for effective solid angle calculations and elemental concentration calculations (JSI)

correction/uncertainty assessment at high count rates Procedures used to correct for losses in the analyzer due to high count rates; e.g., set up and validation of loss-free counting hardware, use of mathematical corrections for pulse pileup as a function of analyzer dead time, etc. Level of difficulty increases with the magnitude of the correction.

KRISS, JSI

%Dead-time was within a range of 0.2 % - 3.0 %. Correction for pile-up < 0.1% (KRISS). Measurements were carried out at such distances that the dead time was kept below 5% with negligible random coincidences, Multichannel analyzer DSPECPLUSTM in ZDT mode was used (JSI)

Corrections for neutron absorption or scattering differences between samples and standards Procedures used to correct for differences between neutron exposure of samples and standards associated with differences in the absorbing and scattering power; e.g., corrections derived from measurements of different amounts of materials or thicknesses of materials, or calculations based on cross-section values to correct for neutron attenuation. Level of difficulty increases with the magnitude of the correction.

KRISS, JSI

Major composition of the sample is nearly the same as that of cellulous filter paper (standard comparator) (KRISS). Samples and standards (Al-0.1% Au IRMM-530RA) were stacked together and fixed in a polyethylene ampoule in sandwich form and irradiated for 20 hours in the CF of TRIGA reactor. Standard Al-0.1% Au (nuclide Au-198 (T1/2=2.695 d) at gamma line of 411.8 keV) was used for axial flux

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gradient corrections in the sample. Radial flux gradient is negligible due to similar diameter of sample and standard. Thermal and epithermal self-shielding factors are equal to 1 (JSI)

corrections for gamma-ray attenuation in samples/standards Procedures used to correct for differences in gamma-ray attenuation between samples and standards; typically relevant only for high-z sample or standard matrices and where samples and standards differ. Level of difficulty increases with the magnitude of the correction.

KRISS, JSI

Major composition of the sample is nearly the same as that of cellulous filter paper (standard comparator) (KRISS). Corrections for gamma-ray attenuations in sample/standard were calculated by Kayzero for Windows (KayWin®)software via effective solid angle calculations. Different measuring distances from the top of an HPGe detector for sample and standard can be used due to absolutely calibrated HPGe detector. The HyperLab program was used for net peak area evaluation in the gamma spectrum (JSI).

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CCQM Study: CCQM-K89 Trace & Essential Elements in Herba Ecliptae

Institute: PTB Method: Ion chromatography with iteratively matrix-matched calibration

solutions using Cs as an internal standard, sample/reference bracketing Analytes: Ca

Core Capability Not tested Tested Specific challenges encountered


PTB

Digestion/dissolution of organic matrices All techniques and procedures used to bring a sample that is primarily organic in nature into solution suitable for liquid sample introduction to the ion chromatography system.

PTB

Calibration of analyte concentration The preparation of calibration standards and the strategy for instrument calibration. Includes external calibration and standard addition procedures as well as the use of an internal standard.

PTB matrix matched calibration solutions needed (PTB)

Signal detection The detection and recording of the analyte signals. The degree of difficulty increases for analytes present at low concentrations.

PTB internal standard necessary (PTB)

Peak integration Procedures used to determine peak areas. (e.g., high difficulty for small peak areas on complex or elevated baselines, especially in case of incomplete peak separation.)

PTB

Ion chromatographic separation All efforts made to separate the analyte peak from other peaks. E.g. choice of eluent(s), isocratic/gradient elution, design of gradient, separation column parameters, type of stationary phase, temperature, flow, …

PTB

Dry mass correction Choice and preparation/preconditioning of desiccant (drying agent), mass determination (control of electrostatic charges, air buoyancy correction), recognition of “stability”

PTB long time (30 d) to reach stable masses using the recommended drying reagent (PTB)

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