CCQM-K43 final report - BIPM · December 2005 CCQM-K43 As, Hg, Pb, Se and Methylmercury in Salmon FINAL REPORT Y. Aregbe and P.D.P. Taylor With contributions from: J. Vogl and A

December 2005

CCQM-K43

As, Hg, Pb, Se and Methylmercury in Salmon

FINAL REPORT

Y. Aregbe and P.D.P. Taylor

With contributions from: J. Vogl and A. Berger from BAM U. Sansone, M. J. Campell, A. Toervenyi from IAEA M. Gallorini and E. Rizzio from IMGC T. de Oliveira Araujo from INMETRO C. Quétel, J. Snell and P. Robouch from IRMM P. Vermaercke from SCK-CEN E. Hwang from KRISS R. Hearn, J. Entwisle, D. Curtis and R. Wahlen from LGC Ltd. G. Labarraque from LNE R. Greenberg, E. Mackey, G. Turk, M. Schantz, S.J. Christopher, W.C. Davis, and S.E. Long from NIST L. Mackay, R. Myors from NMIA K. Inagaki from NMIJ R. Sturgeon, L. Yang from NRC

The Mission of IRMM is to promote a common European measurement system in support of EU policies, especially health and consumer protection, environment, agriculture, internal market and industrial standards. European Commission Directorate-General Joint Research Centre Institute for Reference Materials and Measurements Contact information Yetunde Aregbe European Commission Directorate-General Joint Research Centre Institute for Reference Materials and Measurements Retieseweg 111 B-2440 Geel • Belgium Email: [email protected] Tel.: +32 (0)14 571 673 Fax: +32 (0)14 571 865 http://www.irmm.jrc.be http://www.jrc.cec.eu.int Legal Notice Neither the European Commission nor any person acting on behalf of the Commission is responsible for the use, which might be made of the following information. A great deal of additional information on the European Union is available on the Internet. It can be accessed through the Europa server http://europa.eu.int Luxembourg: Office for Official Publications of the European Communities © European Communities, 2005 Reproduction is authorised provided the source is acknowledged Printed in Belgium

Contents ABSTRACT 1

INTRODUCTION 2

RATIONALE OF THIS COMPARISON 2

PARTICIPATION IN CCQM-K43 3

THE SALMON SAMPLE 4

HOMOGENEITY CHARACTERISATION 4

PARTICIPANT COORDINATION 4

CCQM-K43 INFORMATION DOCUMENTS 5 PROTOCOL FOR DRY-MASS CORRECTION 5 UNCERTAINTY EVALUATION 5 ANALYTICAL METHODS AND TECHNIQUES 7

CCQM-K43 PARTICIPANT’S RESULT 9

THE CCQM-K43 KEY COMPARISON REFERENCE VALUE 10

THE CCQM-K43 GRAPHS 11

DISCUSSION 11

CONCLUSION 12

ACKNOWLEDGEMENTS 12

LIST OF ABBREVIATIONS 13

REFERENCES 14

Annex 1 15 Annex 2 29 Annex 3 41 Annex 4 49

CCQM-K43 Final Report

1

Abstract CCQM-K43 was organised as a follow-up key comparison to the previous pilot study on tuna fish. CCQM-K43 was an activity of the Inorganic Analysis Working Group (IAWG) of CCQM and was coordinated by the Joint Research Centre-Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) of the European Commission (EC). In CCQM-K43 the amount contents of As, Hg, Pb, Se and Methylmercury (CH3Hg) in salmon (muscle and skin) were the measurands under investigation. Results were reported by 12 NMIs. During the CCQM-IAWG autumn meeting in Berlin, October 2005, it was agreed that in CCQM-K43 the KCRV is calculated as the mixture model median (MM-median) of all reported results. The reported results of the NMIs fall within a range of ± 5% for arsenic and of ± 2% for lead and mercury relative to the KCRV. For selenium the spread of all laboratories but one is ± 8%. Also, for methlymercury 4 of the 5 participating NMIs reported results within 4% deviation from the KCRV. The methods applied were isotope dilution mass spectrometry (IDMS) using sector field or quadrupole inductively coupled plasma-mass spectrometry (ICP-MS) or thermal ionisation mass spectrometry (TIMS), external calibration using ICP-MS or atomic absorption spectrometry (AAS). Instrumental neutron activation analysis (INAA) and k0-neutron

activation analysis (k0-NAA) were also used as analytical techniques. This report presents the participants’ results in CCQM-K43 for all analytes under investigation. In Annex 1, the results with the KCRV, the equivalence statements and the results sorted according to analytical technique applied are presented. In Annex 2, the different approaches for methlymercury measurements are presented in more detail. In Annex 3, the questionnaire data are presented. Annex 4 compiles all the CCQM-K43 information documents. The pilot study CCQM-P39.1 was carried out in parallel to this key comparison for the same measurands in the same salmon material Participation was meant for IAWG members, who did not immediately want to report results in a key comparison, and invited expert laboratories.

CCQM-K43 As, Hg, Pb, Se and Methylmercury in Salmon

2

Introduction The previous pilot study CCQM-P39 on tuna fish [1] was proceeded in autumn 2004 to this key comparison, CCQM-K43, and the pilot study, CCQM-P39.1. In alignment with the previous CCQM-P39 on tuna fish the choice of analytes under investigation in CCQM-K43 were exactly the same. The purpose of CCQM-K43&P39.1 was to demonstrate the measurement capability of determining the amount content of metals in a more challenging ‘real-life’ fish sample, with significantly lower mercury content as the preceding tuna fish sample, but with similar arsenic, lead and selenium content, in order to demonstrate ‘how far the light shines’. NMIs participating in CCQM-K43 could demonstrate their measurement capabilities over an order of magnitude concentration range, particularly on total mercury and or-ganomercury. Furthermore the matrix ‘salmon muscle and skin’ was from an analytical sample pretreatment point of view more challenging than the freeze-dried tuna muscle powder used in CCQM P39. CCQM-K43 was further broadening the scope and degree of difficulty of measurements in a key comparison addressed by the CCQM-IAWG. Rationale for this comparison In order to protect public health it is essential to keep contaminants at levels which are toxicologically acceptable. Thus surveillance measures are taken regarding the presence of contaminants in foodstuff, including fish. Mercury is a potential environmental toxin. The main source of human intake of mercury contaminants originates from methylmercury in fish and fish products. Methylmercury is particularly interesting due to its high toxicity compared to inorganic mercury and its high proportion among organomercury species in the environment. Mercury species may induce alterations in the normal development of the brain of infants and may induce neurological changes in adults.

Lead may induce reduced cognitive development in children and increased blood pressure and cardio-vascular diseases in adults. To protect public health, maximum levels of mercury and lead in fish products are laid down in relevant regulations. The EC Directive 2001/22 describes the community methods for the sampling, the sample preparation and the analysis of mercury and lead in fish [2]. The EC Regulation (466/2001) endorses officially the threshold value of 0.5 mg·kg-1 mercury and

0.2 mg·kg-1 lead in salmon [3]. Selenium is an essential trace element for human beings. Seafood is an important source of selenium intake for people in some regions. Certain forms of cancer and cardiovascular diseases have also been associated with selenium deficiency. Selenium is also counted among the most important elements in terms of food-chain contamination. Selenium has the narrowest plateau between concentrations that show deficiency and toxic effects, respectively. Recently, the EC requested the Scientific Committee on Food (SCF) to re-view the upper level of daily intake of individual vitamins and minerals, amongst them selenium, and to pro-vide the basis for the establishment of safety factors [4]. Rules for measurements of arsenic are set in the commission decision on implementing Council Directive 96/23/EC concerning the performance of analytical methods and the interpretation of results [5].


3

Participation in CCQM-K43

CC CC QQ MM -- KK 44 33 PP AA RR TT II CC II PP AA NN TT CC OO UU NN TT RR YY

IAWG members

BAM Bundesanstalt für Materialforschung und –prüfung

Germany

IAEA International Atomic Energy Agency

United Nations

IMGC Institute of Metrology G. Colonnetti - University of Pavia

Italy

INMETRO Instituto Nacional de Metrologia, Normalização e Qualidade Industrial

Brazil

IRMM Institute for Reference Materials and Measurements

European Commission

KRISS Korea Research Institute of Standards and Science

Republic of Korea

LGC Ltd. Laboratory of the Government Chemist

United Kingdom

LNE Laboratoire National d’ Essais

France

NIST National Institute of Standards and Technology

United States of America

NMIA National Measurement Institute - NARL Primary Methods

Australia

NMIJ National Metrology Institute of Japan

Japan

NRC National Research Council Canada

Canada


4

The salmon sample The CCQM-K43 fish sample is a freeze dried and ground salmon muscle and skin powder bottled in amber glass vials each one containing about 2.2g. Each participant received 4 salmon samples (8-10g) to account for the small unit size. Participants were asked to analyse at least 2 sample aliquots from 2 bottles for each measured analyte. This salmon originates from Norway and is a real-life sample. The range of lead amount content in the salmon was just slightly exceeding the upper limit as stated in the EC Regulation (466/2001), whereas the mercury content was far below the upper legislation limit [3]. Therefore, this salmon material was perfectly appropriate for the purpose of a CCQM key comparison complementary to the previous pilot study on tuna fish, which exceeded the upper limit for mercury [1]. Homogeneity characterisation Within and between bottle homogeneity tests for Pb were carried out on 10 sub-samples of 10 bottles using solid sample Zeemann AAS (SS-ZAAS) and for Hg and MeHg on 3 sub-samples from 6 bottles applying IDMS. For As and Se, the homogeneity was assessed by analysing 2 sub-samples from 10 bottles applying k0-NAA. Results from these measurements were evaluated accordingly and compared to the procedures established in ISO Guide 35:1989 for the certification of reference materials based on analysis of variance ANOVA [6, 7]. The between bottle homogeneity of all 5 analytes was ranging from 0.5% - 2.5%, which was found to be adequate for this key comparison. These results were also confirmed by the observed spread of the participants’ results, where each reported result of the total amount content represents at least measurements of 2 sub-samples from 2 bottles.

Participant Coordination According to the rules for participation in key comparisons only IAWG members who meet the requirements given in paragraph 6 of the MRA could participate in CCQM-K43 [8]. The call for participation was circulated to the NMIs in October 2004. The information package containing the salmon samples was sent to all registered participants in December 2004. The participants were asked to register for participation and to report their results and questionnaire answers online via the IRMM IT system for Interlaboratory Comparisons, called MILC. The first deadline for result reporting was 31st March 2005, which was finally extended to 4th April 2005. The results were presented at the Spring IAWG meeting in April at BIPM. In summer 2005, a summary report was circulated amongst all participants for confirmation of the reported results and applied analytical methods. Final results and proposal for the KCRV were presented at the last CCQM-IAWG meeting in Berlin in October 2005.


5

CCQM-K43 information documents

o Letter to the participants pointing out the deadlines

o Scope of the CCQM-K43 key comparison

o General instructions o Instructions for online result and

questionnaire reporting in MILC o Instructions for uncertainty evaluation o Instructions for the dry-mass

correction and digestion of the salmon o Information for CCQM-K43

participants measuring methylmercury, including the ERM AE670 certificate and the publication on the preparation and certification of ERM AE670

Protocol for dry-mass correction The determination of the moisture content of the samples is to some extent “operationally defined” [9, 10]. In view of the comparability of the results, the protocol in CCQM-K43 for correction of the moisture was as follows: “For correction of the measured values to dry-mass, water content measurements should be made on a separate portion of the same material with a mass of 0.6 ± 0.1g. The material should be dried before weighing for a minimum of 24 hours in a ventilated oven at 102 ± 2°C. Cycles of drying and weighing should be repeated until a constant mass is attained. Each weighing has to be carried out after the sample has reached thermal equilibrium at room temperature in a dessicator, time about 30 min. Successive weights should not differ more than 0.001 g. The loss of mass corresponds to the “dry-mass correction factor” that should be applied”. The water content was also determined by Karl-Fischer titration. No significant difference was observed. The reported results in CCQM-K43 for the measured water content in the salmon samples are listed in Table 1.

Uncertainty evaluation The participants were asked to report a complete uncertainty budget with their results. The uncertainty statement should be evaluated and presented according to the principles outlined in, e.g. “ISO/GUM” [11] or the EURACHEM/CITAC Guide [12]. The organising laboratory asked all the participants in CCQM-K43 the following:

o state your measurement equation o identify all significant sources of

uncertainty o state your input quantities o quantify uncertainty components and

convert them to standard uncertainties o calculate the combined standard

uncertainty uc o present an expanded uncertainty U

with the coverage factor k=2 o include factors related to sample

treatment in your measurement equations

o describe the applied evaluation process and type of assumed distribution for your uncertainty estimation

The complete uncertainty statement should be forwarded to the organising laboratory as attachment to the result reporting sheets. All participants in CCQM-K43 provided an uncertainty budget with their measurement results.


6

Table 1 Reported values for water content determination and dry-mass correction

CCCCQQMM--KK4433 CC oo rr rr ee cc tt ii oo nn ff oo rr dd rr yy -- mm aa ss ss

PP AA RR TT II CC II PP AA NN TT WW AA TT EE RR CC OO NN TT EE NN TT II NN %% CC OO RR RR EE CC TT II OO NN FF AA CC TT OO RR

BAM 2.1 ± 0.1 0.979 ± 0.001

IAEA 2.2 ± 0.2 0.978 ± 0.002

IMGC 2.07 ± 0.07 0.979 ± 0.035

INMETRO 2.6 ± 0.1 0.9736 ± 0.1

IRMM 2.87 ± 1 0.9713 ± 0.010

KRISS 2.14 ± 0.08 0.9786 ± 0.0008

LGC Ltd. 1.84 ± 0.13 0.9816 ± 0.013

LNE Se: 1.19 ± 0.03; Hg: 2.56 ± 0.18; As: 2.64 ± 0.06

Se: 0.9881 ± 0.0003; Hg: 0.9744 ± 0.0018; As: 0.9736 ± 0.0006

NIST 2.0 ± 0.1 0.98 ± 0.1

NMIA 3.1 1.032 ± 0.008

NMIJ 2.30 ± 0.20 0.9770 ± 0.0020

NRC 2.24 ± 0.225 0.97755 ± 0.00225


7

Analytical methods and techniques Different methods and instrumental techniques besides IDMS were applied in CCQM-K43. The methods applied were:

o isotope dilution mass spectrometry (IDMS) using sector field or quadrupole inductively coupled plasma-mass spectrometry (ICP-MS)

o external calibration using ICP-MS o atomic absorption spectrometry (AAS)

o Instrumental neutron activation analysis (INAA) and k0-neutron activation analysis (k0-NAA)

The analytical methods and instrumental techniques are listed in Table 2 and Table 3. In Annex 1 of this report, all the results are graphically presented sorted by analytical technique

Table 2 Analytical methods and instrumental techniques in CCQM-K43 for methylmercury

CCCCQQMM--KK4433 aa nn aa ll yy tt ee :: MM ee HH gg

PP AA RR TT II CC II PP AA NN TT AA NN AA LL YY TT II CC AA LL MM EE TT HH OO DD II NN SS TT RR UU MM EE NN TT AA LL TT EE CC HH NN II QQ UU EE

IRMM direct IDMS using ERM-AE670 as spike GC-ICP-MS

LGC Ltd. double IDMS using ERM-AE670 as spike LC-ICP-MS

NIST combined method using ERM AE670 and SRM 3133 as spike

GC-MS + SID-GC-ICPMS

NMIJ double IDMS using ERM-AE670 as spike GC-ICP-MS

NRC IDMS + reverse IDMS, using NRCC EOM-1 as spike GC-SF-ICP- MS


8

Table 3 Analytical methods and instrumental techniques in CCQM-K43 for As, Hg, Pb, Se

CCCCQQMM--KK4433 aa nn aa ll yy tt ee :: AA ss ,, HH gg ,, PP bb ,, SS ee

PP AA RR TT II CC II PP AA NN TT AA NN AA LL YY TT II CC AA LL MM EE TT HH OO DD II NN SS TT RR UU MM EE NN TT AA LL TT EE CC HH NN II QQ UU EE

BAM As, Se: NAA Pb: IDMS

As, Se: INAA Pb: TIMS

IAEA external calibration As, Pb: ICP-MS+GF-AAS Se: ICP-MS

IMGC NAA INAA

INMETRO NAA INAA

IRMM As, Se: NAA Hg: IDMS

As, Se: K0-NAA Hg: ICP-QMS

KRISS Double IDMS Pb: ICP-QMS Hg: ICP- magnetic sector field MS

LGC Ltd. matching double IDMS Hg: ICP- magnetic sector field MS l Se: ICP-MS with collision cell

LNE As: standard addition Hg : IDMS Se: double IDMS

As, Se: ICP-QMS with CCT Hg: ICP- magnetic sector field MS

NIST As, Se: NAA Hg: IDMS

As, Se: INAA Hg: CV-ICP-MS

NMIA As: As: standard addition Pb, Hg, Se: matching double IDMS ICP-MS with collision cell

NMIJ As: internal standardisation Hg, Pb, Se: double IDMS ICP-MS with an octopole reaction cell

NRC IDMS ICP-magnetic sector field MS


9

CCQM-K43 participant’s result The CCQM-K43 participants’ results, as reported to the organising institute, are listed in Table 4.

Table 4 CCQM-K43 participants reported results

REPORTED RESULTS AND EXPANDED UNCERTAINTY (k=2) in 10-6 mol·kg-1

Participant As Hg MeHg Pb Se

BAM 58.75 ± 2.64 - - 3.800 ± 0.081 7.43 ± 0.44

IAEA 59.47 ± 0.78 - - 3.79 ± 0.12 9.20 ± 0.85

IMGC 55.86 ± 1.02 - - - 7.18 ± 0.26

INMETRO 58.00± 2.20 - - 7.47 ± 0.46

IRMM 57.80± 2.70 0.3856 ± 0.0083 0.371 ± 0.017 - 7.13 ± 0.38

KRISS - 0.3859 ± 0.0026 - 3.82 ± 0.13 -

LGC - 0.398 ± 0.016 0.372± 0.025 - 7.04 ± 0.43

LNE 56.17 ± 2.54 0.394 ± 0.019 - - 7.97 ± 0.32

NIST 57.59 ± 0.75 0.3859 ± 0.0086 0.324 ± 0.011 - 7.58 ± 0.18

NMIA 59.4 ± 3.4 0.389 ± 0.016 - 3.92 ± 0.17 7.17 ± 0.28

NMIJ 60.86± 3.10 0.3921 ± 0.0069 0.3880 ± 0.0091 3.83 ± 0.24 7.15 ± 0.11

NRC - 0.387 ± 0.015 0.375 ± 0.019 - -


10

The CCQM-K43 KCRV At the CCQM meeting in Paris in April 2004, David L. Duewer from NIST presented a robust approach for the determination of CCQM Key Comparison Values and Uncertainties to the IAWG members [13]. He introduced the mixture model probability density function (MM-PDF) for each measurement population as a means of data analysis for key comparisons and pilot studies. MM-PDF based summary statistics enable estimation of the expected performance of the majority of participants of a key comparison or pilot study [14]. The “true value” of a measurand in a given material can be estimated in a robust way even when some of the results are not in accordance with the majority. During the last autumn IAWG meeting in Berlin, the mixture model median (MM-median) and the MM-

median based Standard Deviation S(MM-Median) was chosen as robust estimation of the KCRV in CCQM-K43. In the table below the KCRV_MM-median, the mean and the median are listed for all the analytes in CCQM-K43 as µ ± σ*ts/ √n which is the 95% confidence interval on µ for n reported results. From Table 5 it can be seen that there is no significant difference of the KCRV com-pared to the mean and the median. The MM-median is closely related to the median. It is robust to outliners, but also accounts for the reported uncertainty of each participant. It can be seen that the MM-median gives a reliable robust estimate of the KCRV even for deviation of one of the results from the majority of reported results.

Table 5 CCQM-K43 summary statistics to establish the KCRV

µ ± σ*ts / √n in 10-6 mol·kg-1

As Hg MeHg Pb Se

KCRV_MM-median 58.1 ± 1.5 0.3884 ± 0.0056 0.373 ± 0.023 3.82 ± 0.10 7.32 ± 0.28

mean 58.2 ± 1.2 0.3897 ± 0.0038 0.366 ± 0.031 3.832 ± 0.064 7.53 ± 0.46

median 58.0 ± 1.6 0.3880 ± 0.0028 0.372 ± 0.0055 3.821 ± 0.039 7.31 ± 0.18


11

The CCQM-K43 graphs The CCQM-K43 results for As, Hg, Pb and Se are presented graphically in Annex 1 of this report. In the first 4 graphs, all CCQM K43 results are plotted in ascending order, including the KCRV. In the following 8 graphs the equivalence tables and equivalence charts are presented. The degree of equivalence of each laboratory with respect to the KCRV is given by: Di = (xi – xR), xi being the reported measurement results of laboratory i and xR being the KCRV and Ui, its expanded uncertainty (k = 2), Ui

2 = (ki2ui

2 + kR2uR

2), both expressed in µmol•kg-1. The last 4 graphs in Annex 1 plot the results according to applied

analytical technique with the KCRV and the mixture model probability density function. On these MM-PDF graphs also the spread of the population of results is included. To enable the comparison of the spread of data, the scale of all graphs is ± 50 % deviation with respect to the KCRV. In Annex 2 the results and questionnaire data for MeHg are presented and discussed in more detail. Table 6 summarises all the CCQM-K43 graphs of Annex 1 and Annex 2.

Table 6 CCQM-K43 graphs

General Graphs - Annex 1 As, Hg, Pb and Se

All participants with KCRV

Equivalence charts

Analytical techniques

Methylmercury Graphs - Annex 2 MeHg (CH3Hg)

All participants with KCRV

Analytical techniques

Equivalence chart

All participants - Results with amended NIST value

Discussion All NMIs that participated in CCQM-K43 had previously participated in the pilot study on tuna fish, except INMETRO. As can be seen from Table 4 and the graphs in Annex 1 and Annex 2, the agreement of measurement results between NMIs is very good. The reported results of the NMIs fall within a range of ± 5% for arsenic and of ± 2% for lead and mercury relative to the KCRV. For selenium the spread of all laboratories but IAEA is ± 8%.

From previous IAEA experience with Zn measurements by ICP-MS, it was assumed that the Se value is higher due to divergent behaviour between the analyte and the internal standard as a consequence of inadequate matching of nitric acid strength between standards and samples. In spite of clear evidence that this was indeed the reason for the bias of the IAEA result, the IAEA Se result was not discarded when calculating the KCRV.


12

Also, for methlymercury 4 of the 5 participating NMIs reported results within 4% deviation from the KCRV. NIST reported for MeHg a combined result using GC-MS and SID-GC-ICP-MS. This reported NIST result deviates more than 10% from the other participants’ results. NIST could not identify any problems with the reported GC-MS result, but only with the reported SID-GC-ICP-MS result, as explained in Annex 2. Therefore the NIST result was also taken into account when calculating the KCRV for MeHg. Conclusion The ‘light shines very far’ for the determination of metals in fish tissue when drawing the conclusion from CCQM-K43 and CCQM-P39. Due to the fact that this salmon material was a more challenging ‘fatty’ matrix compared to the dry tuna powder used in CCQM-P39 and due to the fact that the mercury amount content was 2 orders of magnitude lower than the one in the tuna fish sample, the salmon was an excellent choice for the proceeding of CCQM-P39 to this key comparison. The analytes under investigation in CCQM-K43 have been measured with different techniques. This confirms what could already be seen in the previous pilot study on tuna fish. For this kind of analysis, reliable measurements of highest metrological quality can be performed with various instrumental techniques (ICP-MS, AAS, NAA and k0 NAA) and analytical methods (IDMS, external calibration, standard addition and non destructive analysis). They are not method dependent. CCQM-K43 is also a good example of a key comparison in parallel to a pilot study involving not only the NMIs, but also expert laboratories of their countries as it is one of the NMIs’ major tasks to disseminate metrological principles and good measurement practice to the laboratories in their countries. After the agreement of all participants, the final report of the pilot study CCQM-P39.1 will also be

published in the metrologia technical supplement. The main purpose of any Interlaboratory Comparison, thus also of CCQM comparisons, is to assess capabilities and to discover problems and correct analytical procedures accordingly. In this sense NMIs with a result significantly deviating from the KCRV immediately benefited from participating in CCQM K43. The organising laboratory appreciates that IAEA and NIST are sharing this experience with all the other participants. All NMIs have proven with their participation in CCQM-K43 (salmon) and the previous CCQM-P39 (tuna fish) not only their measurement capabilities on measurements close to legal limits, but also on low trace level measurements. In addition they have demonstrated their capability on appropriate sample treatment for a wide range of fish samples. This key comparison therefore serves perfectly to support CMCs of those NMIs in Appendix C. Acknowledgements Special thanks to F. Ulberth and A. Held from the RM unit for their support in providing the suitable salmon sample and in the design of the homogeneity study. The authors acknowledge furthermore the input of all the IRMM scientists who contributed to the reprocessing and characterisation of the tuna fish sample : - K. H. Grobecker, M. Bickel, A. Michiels, A. Bernreuther, S. Yazgan, P. Conneely. Furthermore the assistance of our MILC administrator S. Bynens is warmly acknowledged and the support of M. Sargent as chairman of the CCQM IAWG.


13

List of abbreviations

AAS Atomic Absorption Spectrometry BIPM Bureau International des Poids et Mesures (Paris, France) CCQM Comité Consultatif pour la Quantité de Matière CITAC Co-operation for International Traceability in Analytical Chemistry CRMs Certified Reference Materials EC European Commission EU European Union EURACHEM A focus for Analytical Chemistry in Europe GC-ID-ICP-MS Gas Chromatography Isotope Dilution Inductively Coupled Plasma Mass

Spectrometry GUM Guide for expression for Uncertainty in Measurement IAWG Working Group on Inorganic Analysis ICP-MS Inductively Coupled Plasma-Mass Spectrometry IDMS Isotope Dilution Mass Spectrometry INAA Instrumental Neutron Activation Analysis IRMM Institute for Reference Materials and Measurements (EC, Geel, Belgium) ISO International Organisation for Standardisation JRC Joint Research Centre Ko-NAA Neutron Activation Analysis with k0 standardization MM-median Mixture Model Median MM-PDF Mixture Model Probability Density Function NAA Neutron Activation Analysis NMIs National Metrology Institutes SCF Scientific Committee on Food SS-ZAAS Solid Sample Zeemann Atomic Absorption Spectrometry


14

References

1. Aregbe Y., Quétel C., Taylor P.D.P., CCQM-P39: As, Hg, Pb, Se and methylmercury in tuna fish, Metrologia, 2004, 41, Tech. Suppl., 08004

2. Commission Directive 2001/22/EC laying down the sampling methods of anlysis for the official control of lead, cadmium, nmercury and 3-MCPD in foodstuffs Official Journal of the European Communities L77/14, 08/03/2001

3. Commission Regulation (EC) No 466/2001 of 8 March 2001 setting maximum levels for certain contaminants in foodstuff, Official Journal of the European Communities L077, 16/03/2001, 0001-0013

4. SCF/CS/NUT/UPPLEV/11 FINAL, Nov/2000

5. Commission Decision No 2002/657/EC of 17 August 2002 implementing Coucil Directive 96/23/EC concerning performance of analytical methods and the interpretation of results, Official Journal of the European Communities L221, 17/08/2002

6. T. P. J. Linsinger et al. Accred.Qual.Assur (2001) 6:20-25

7. A.M.H. van der Veen et al. Accred.Qual.Assur (2001) 6:26-30

8. http://www.bipm.org/utils/en/pdf/mra.pdf 9. S. Rückhold et al. Fresenius J. Anal. Chem

(2000) 368: 522-527

10. S. Rückhold et al . Fresenius J. Anal. Chem (2000) 370: 189-193

11. International Organisation for Standardisation, “Guide to the Expression of Uncertainty in Measurement”, ©ISO, ISBN 92-67-10188-9, Geneva, Switzerland, 1993.

12. Eurachem/CITAC Guide Quantifying uncertainty in analytical measurement (2nd ed. 2000), www.eurachem.bam.de

13. David L. Duewer, A robust approach for the determination of CCQM key comparison reference values and uncertainties, Working document CCQM 04-15, BIPM, 2004

14. P. Ciarlini, M. Cox, F. Pavese, G.

Regoliosi. The use of a mixture of probability distributions in temperature interlaboratory comparisons. Metrologia 2004;41:116-121

15

Annex 1 – Graphical presentation Contents CCQM-K43: As, Hg, Pb, Se and Methylmercury in Salmon

Figures 1 - 4 _________________________________________________________ 18-19 All participants with KCRV _________________________________________________

Figures 5 - 12 ________________________________________________________ 22-25 Equivalence charts________________________________________________________

Figures 13 - 16 _______________________________________________________ 27-28 Analytical techniques ______________________________________________________

16

17

CCQM-K43: As, Hg, Pb, Se and Methylmercury in Salmon

Annex 1 – All participants results

Figure General Graphs Page number

Figure 1 All participants - As 18

Figure 2 All participants - Hg 18

Figure 3 All participants - Pb 19

Figure 4 All participants - Se 19

CCQM-K43 As, Hg, Pb, Se and Methylmercury in Salmon - Annex 1

18

NMIJ

IAEANMIABAMINMETROIRMM

NIST

LNEIMGC

46.48

51.48

56.48

61.48

66.48

c

10

-6 m

ol·k

g-1

-20

-15

-10

-5

0

5

10

15

20

Dev

iatio

n fr

om th

e M

M-m

edia

n in

%

CCQM-K43: As in salmonKCRV_Mixture Model-median: 58.1 ± 1.5 ·10-6 mol·kg-1 ; [ µ ± σ*ts/√n]

IRMMKRISS NIST

NRC NMIANMIJ LNE

LGC

0.31

0.33

0.35

0.37

0.39

0.41

0.43

0.45

c

10

-6 m

ol·k

g-1

-20

-15

-10

-5

0

5

10

15

20

Dev

iatio

n fr

om th

e M

M-m

edia

n in

%

CCQM-K43: Hg in salmonMixture Model-median: 0.3884 ± 0.0056 ·10-6 mol·kg-1 ; [ µ ± σ*ts/√n]

Figure 1

Figure 2

CCQM-K43 Final Report - Annex 1

19

IAEA BAM

KRISS NMIJ

NMIA

3.06

3.26

3.46

3.66

3.86

4.06

4.26

4.46

c

10

-6 m

ol·k

g-1

-20

-15

-10

-5

0

5

10

15

20

Dev

iatio

n fr

om th

e M

M-m

edia

n in

%

CCQM-K43: Pb in salmonKCRV_Mixture Model-median: 3.82 ± 0.10 ·10-6 mol·kg-1; [ µ ± σ*ts/√n]

IAEA

LNE

NISTINMETROBAMIMGCNMIANMIJIRMMLGC

3.66

4.66

5.66

6.66

7.66

8.66

9.66

10.66

c

10

-6 m

ol·k

g-1

-50

-40

-30

-20

-10

0

10

20

30

40

50

Dev

iatio

n fr

om th

e M

M-m

edia

n in

%

CCQM-K43: Se in salmonMixture Model-median: 7.32 ± 0.28 ·10-6 mol·kg-1 ; [ µ ± σ*ts/√n]

Figure 3

Figure 4


20

21


Annex 1 – All participants – Degree of equivalence

Figure Degree of equivalence Page number

Figure 5 Equivalence Table - As 22

Figure 6 Equivalence chart- As 22

Figure 7 Equivalence Table - Hg 23

Figure 8 Equivalence chart - Hg 23

Figure 9 Equivalence Table - Pb 24

Figure 10 Equivalence chart - Pb 24

Figure 11 Equivalence Table - Se 25

Figure 12 Equivalence chart - Se 25


22

Figure 5 Degree of equivalence – As

Lab i

D i U i

BAM 0.65 3.04IAEA 1.37 1.69IMGC -2.24 1.81

INMETRO -0.10 2.66IRMM -0.30 3.09LNE -1.93 2.95NIST -0.51 1.68NMIA 1.30 3.72NMIJ 2.76 3.44

µmol·kg-1

Figure 6 Equivalence chart - As

Degree of equivalence CCQM-K43: As in salmon; U iR2 = U i

2 + U R2

BAM

IAEA

IMGC

INMETRO

IRMMLNE

NIST NMIA

NMIJ

-8.0

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

equi

vale

nce

( Di)

µm

ol·k

g-1


23

Figure 7 Degree of equivalence – Hg

Figure 8 Equivalence chart - Hg

Degree of equivalence CCQM-K43: Hg in salmon; U iR2 = U i

2 + U R2

LNEIRMM

KRISS

LGC

NIST NMIA

NMIJ

NRC

-0.04

-0.03

-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

equi

vale

nce

( Di)

µm

ol·k

g-1

Lab i

D i U i

LNE 0.0056 0.0198IRMM -0.0028 0.0100KRISS -0.0025 0.0062LGC 0.0096 0.0170NIST -0.0025 0.0103NMIA 0.0006 0.0170NMIJ 0.0037 0.0089NRC -0.0014 0.0160

µmol·kg-1


24

Figure 9 Degree of equivalence – Pb Figure 10 Equivalence chart - Pb

Degree of equivalence CCQM-K43: Pb in salmon; U iR2 = U i

2 + U R2

IAEA NMIA

BAM

NMIJ

KRISS

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

equi

vale

nce

( Di)

µm

ol·k

g-1

Lab i

D i U i

IAEA -0.03 0.15NMIA 0.10 0.20BAM -0.02 0.13NMIJ 0.01 0.26

KRISS 0.00 0.17

µmol·kg-1


25

Figure 11 Degree of equivalence – Se Figure 12 Equivalence chart - Se

Degree of equivalence CCQM-K43: Se in salmon; U iR2 = U i

2 + U R2

IAEA

LNENIST

INMETROBAMIMGCNMIANMIJIRMMLGC

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

equi

vale

nce

( Di)

µm

ol·k

g-1

Lab i

D i U i

LGC -0.28 0.51IRMM -0.19 0.47NMIJ -0.17 0.30NMIA -0.15 0.40IMGC -0.14 0.38BAM 0.11 0.52

INMETRO 0.15 0.54NIST 0.26 0.33LNE 0.65 0.43IAEA 1.88 0.89

µmol·kg-1


26


Annex 1 – All participants – Analytical techniques

Figure Method graphs Page number

Figure 13 Analytical techniques, All participants - As 27

Figure 14 Analytical techniques, All participants - Hg 27

Figure 15 Analytical techniques, All participants - Pb 28

Figure 16 Analytical techniques, All participants - Se 28

27

Figure 13 Results for As from all CCQM-K43 participants sorted by analytical method

LNE

NM

IA

NM

IJ

IAE

A

IMG

C

NIS

T

IRM

M

INM

ETR

O

BA

M

5040

3020

100

-10

-20

-30

-40

-50

Dev

iatio

n fro

m M

M-m

edia

n in

%

IC P -M S

IC P -M S + G F-A A S

N A A

Figure 14 Results for Hg from all CCQM-K43 participants sorted by analytical method

IRM

M

KR

ISS

NIS

T

NR

C

NM

IA

NM

IJ

LNE

LGC

5040

3020

100

-10

-20

-30

-40

-50

Dev

iatio

n fro

m M

M-m

edia

n in

% ID-ICP-MS

CCQM-PK43 As, Hg, Pb, Se and Methylmercury in Salmon - Annex 1

28

Figure 15 Results for Pb from all CCQM-K43 participants sorted by analytical method

KR

ISS

NM

IJ

NM

IA

IAE

A

BA

M

5040

3020

100

-10

-20

-30

-40

-50

Dev

iatio

n fro

m M

M-m

edia

n in

%

ID-ICP-MS

ICP-MS + GF-AAS

ID-TIMS

Figure 16 Results for Se from all CCQM-K43 participants sorted by analytical method

LGC

NM

IJ

NM

IA

LNE

IRM

M

IMG

C

BA

M

INM

ETR

O

NIS

T

IAE

A

5040

3020

100

-10

-20

-30

-40

-50

Dev

iatio

n fro

m M

M-m

edia

n in

%

ID-ICP-MS

k0-NAA

NAA

29

Annex 2 – Methylmercury (CH3Hg) Contents CCQM-K43: As, Hg, Pb, Se and Methylmercury in Salmon METHYLMERCURY MEASUREMENTS 31

DISCUSSION 32

QUESTIONNAIRE DATA 36-39

REFERENCES 40

30

31


Annex 2 – All participants results Methylmercury (CH3Hg)

Figure/ Table Page

number

Figure 1 All participants - MeHg 33

Figure 2 Analytical techniques, All participants - MeHg 33

Figure 3 Equivalence Table - MeHg 34

Figure 4 Equivalence chart - MeHg 34

Figure 5 All participants - MeHg with NIST amended value 35

Table 1 Measurement strategy 36

Table 2 Timing of the spike addition for ID or SA & ref. isotope used for IDMS 37

Table 3 Measurement process 38

Table 4 Experimental reproducibility from the different sample aliquots 39


32

Methylmercury measurementsAll participants who measured methylmercury in CCQM-K43 had previously participated in CCQM-P39 (tuna fish). A detailed evaluation of the CCQM-P39 results for the MeHg measurements was recently published in the open literature [1]. Therefore they had already received during this previous pilot study the ERM AE670 202Hg enriched spike solution. Participants were not asked to use it, but were entirely free to implement the measurement method of their choice. The ERM AE670 material was offered for use by those applying species specific direct IDMS. In addition the final ERM AE670 certificate and the publication on the preparation and certification of the ERM AE670 [2], were also forwarded to all CCQM-K43 participants who measured methylmercury. ERM AE670 is distributed under the European Reference Materials programme [3]. All CCQM-K43 participants implemented an IDMS approach with GC- or LC-ICP-MS. IRMM, LGC and NMIJ used the ERM AE670 as spike material for the isotope dilution. NIST reported a combined result for MeHg using GC-MS and speciated isotope dilution GC-ICP-MS. NIST used ERM AE670 as internal standard for the GC-MS measurements. NIST also used ERM AE670 for their SID-GC-ICP-MS result, but used a value based upon a spike calibration with SRM 3133 (Mercury Solution) rather than the ERM certified value. NRC used its own reference material as spike. Participants measuring MeHg were asked to fill in a separate questionnaire. This Annex summarises the questionnaire data and presents the results and equivalence statements for methylmercury.

Discussion

As shown in Figure 1 – Figure 4, results for MeHg are within 13% relative to the KCRV taking into account all participants’ results. After the CCQM-K43 summary report was distributed to the participants for comments, NIST reinvestigated their methylmercury measurements. They could not find any explanation for the deviation of their GC-MS measurement results compared to the other participants’ results. Therefore the reported NIST result was also included in the calculation of the KCRV. In the case of their SID-GC-ICP-MS result, NIST discovered a problem with the spike calibration procedure that was used. Methylmercury was not fully decomposed by that procedure and thus not properly equilibrated with SRM 3133. As a corrective action NIST performed the calculation with the original data set using the certified value of ERM-AE670. This approach gave as a result for the methylmercury measurements with SID-GC-ICP-MS 0.349 µmol·kg-1 with and expanded

uncertainty of 0.017 µmol·kg-1. Excluding the initially reported NIST MeHg result and taking into account the amended NIST value for SID-GC-ICP-MS, the spread of results for MeHg by the NMIs would fall within 4% deviation from the KCRV. NIST asked the organising laboratory to also include these values in the CCQM-K43 report (see Figure 5). This is a very good example how participation in a pilot study results in immediate correction measures, which is the main purpose for participation in Interlaboratory Comparisons. Furthermore, this example also proves the robustness of the MM-median as KCRV. In Figure 1 and Figure 5 it can be seen that there is no change in the value for the MM-median. This confirms the approach chosen in CCQM-K43 not to exclude any reported result from the calculation of the KCRV, as long as there is no scientific explanation for the observed bias.

CCQM-K43 final report – Annex 2

33

NMIJNRCLGC

IRMM

NIST

0.30

0.32

0.34

0.36

0.38

0.40

0.42

0.44

c

10

-6 m

ol·k

g-1

-20

-15

-10

-5

0

5

10

15

20

Dev

iatio

n fr

om th

e M

M-m

edia

n in

%

CCQM-K43: MeHg in salmonKCRV_Mixture Model-median: 0.373 ± 0.023 ·10-6 mol·kg-1 ; [ µ ± σ*ts/√n]

Figure 1 Results for MeHg from all CCQM-K43 participants

Figure 2 Results for MeHg from all CCQM-K43 participants sorted by instrumental technique

IRM

M

NM

IJ

NIS

T

NR

C

LGC

5040

3020

100

-10

-20

-30

-40

-50

Dev

iatio

n fro

m M

M-m

edia

n in

%

GC-ID-ICP-MS

GC-MS + SID-GC-ICP-MSLC-ID-ICP-MS

GC-SF-ID-ICP-MS


34

Figure 3 Degree of equivalence – MeHg

Figure 4 Equivalence chart - MeHg

Degree of equivalence CCQM-K43: MeHg in salmon; U iR2 = U i

2 + U R2

IRMM LGC

NIST

NMIJ NRC

-0.10

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

0.10

equi

vale

nce

( Di)

µm

ol·k

g-1

Lab i

D i U i

IRMM -0.0020 0.0286LGC -0.0010 0.0340NIST -0.0494 0.0254NMIJ 0.0150 0.0247NRC 0.0020 0.0298

µmol·kg-1


35

Figure 5 Results for MeHg from all CCQM-K43 participants-with NIST amended value for SID-GC-ICP-MS not combined with GC-MS value

NMIJNRCLGC

IRMM

NIST

0.30

0.32

0.34

0.36

0.38

0.40

0.42

0.44

c

10

-6 m

ol·k

g-1

-20

-15

-10

-5

0

5

10

15

20

Dev

iatio

n fr

om th

e M

M-m

edia

n in

%

CCQM-K43: MeHg in salmonMixture Model-median with corrected NIST result: 0.373 ± 0.022 ·10-6 mol·kg-1 ; [ µ ± σ*ts/√n]


36

Questionnaire Data Table 1 Measurement strategy

Participant Direct IDMS

with ERM AE670

Double IDMS with

ERM AE670 Other

method

Calibration with

external matrix

matched standards

Without

an internal

standard

Method of standard addition

(SA) calibration

IRMM

LGC Ltd.

NIST

Average of appproach 1 and

2 (used two different

measurement methods)

NMIJ

NRC

Isotope dilution and reverse

isotope dilution using a 198Hg

enriched Me198Hg

(NRCC EOM-1)


37

Table 2 Timing of the spike addition for ID or SA & ref. isotope used for IDMS

REPORTED QUESTIONNAIRE DATA FOR METHYLMERCURY

Participant

Some hours

prior to MeHg

extraction

Immediately before MeHg

extraction

After MeHg extraction,

prior to measurement

Reference isotope used for

IDMS

Number of replicate

blend samples

IRMM 202Hg 9

LGC Ltd. 200Hg 4

NIST multiple

6 for each of two

measurement methods

NMIJ 200Hg/202Hg 2 samples x 2 bottles

NRC

Isotope pair of 202Hg/198Hg was used for

the determination of MeHg using

species specific ID and

reverse ID method.

4


38

Table 3 Measurement process


Participant Sample mass (g)

Extraction reagents

Extraction apparatus

Derivatisation reagents

Species

separation apparatus

Detector

IRMM ~ 0.2 See ref. [4] See ref. [4] See ref. [4] See ref. [4] See ref. [4]

LGC Ltd. 0.4

Protease type XIV (0.04g), 15ml of 0.1M ammonium phosphate buffer with 0.05% mercaptomethanol

Incubator 37C None LC ICP-MS

NIST 0.25g and 0.5 TMAH, HCl Microwave NaB(C2H5)4

and NaTHBO GC ICP-MS, EIMS

NMIJ ~0.4g 25% KOH/MeOH

ultrasound bath NaBPh4

GC, column: HP-5MS(0.25 um x0.25 mm

x 30 m), carrier: He 1

mL/min

ICP-MS

NRC 0.4 25 % KOH in methanol

Mechanical shaker NaB(C3H7)4 GC ICP-MS

More detailed information on the analytical approaches of the institutes for the determination of methylmercury in fish tissue can be found in [1].


39

Table 4 Experimental reproducibility from the different sample aliquots


Experimental reproducibility

IRMM 1.61%

LGC Ltd. 0.78%

NIST Me-Hg(GCMS)=1.3%, Me-Hg(SID-GC-ICPMS)=2.9%

NMIJ 0.3% (n=4)

NRC 1.7 %


40

References 1. C. R. Quétel et al, Methylmercury in tuna :

demonstrating measurement capabilities and evaluating comparability of results worldwide from the CCQM-P39 comparison, JAAS, 2005, 20, 1058-1066

2. J. P. Snell et al, Preparation and certification

of ERM®-AE670, a 202Hg enriched methylmercury isotopic reference material.., J. Anal. At. Spectrom., 2004, 19, 1315 – 1324

3. http://www.erm-crm.org 4. J. Snell, C. R. Quétel (2005) SI-traceable

certification of methylmercury amount content in a tuna material. Journal of Analytical Atomic Spectrometry, Vol. 20 (4), 447-454

41

Annex 3 – Questionnaire data As, Hg, Pb, Se Contents


Tables 1 - 6 __________________________________________________________ 44-48 Questionnaire data________________________________________________________

42

43


Annex 3 – Questionnaire data

Table Page number

Table 1 Digestion method and acid mixture 44

Table 2 Reference isotope for IDMS 45

Table 3 Number of blends 45

Table 4 Experimental reproducibility 46

Table 5 (Isotopic) reference materials used for calibration 47

Table 6 Number of salmon vials used for the analysis and Use of square root of n for type A uncertainty contributions 48


44

Table 1 Digestion method and acid mixture

REPORTED QUESTIONNAIRE DATA

Participant As Hg Pb Se

BAM - - High pressure asher H2O2, HNO3

-

IAEA Microwave digestion HNO3

- Microwave digestion HNO3

Microwave digestion HNO3

IMGC - - - -

INMETRO - - - -

IRMM - Microwave digestion HNO3, HCl - -

KRISS - Microwave digestion H2O2, HNO3

Microwave digestion H2O2, HNO3

-

LGC Ltd. - Microwave digestion H2O2, HNO3

- Microwave digestion H2O2, HNO3

LNE Microwave digestion H2O2, HNO3


- Microwave digestion H2O2, HNO3

NIST - High pressure microwave digestion HNO3

- -

NMIA Microwave digestion H2O2, HNO3




NMIJ Microwave digestion HClO4, HNO3

Microwave digestion Aqua regia

Microwave digestion HClO4, HNO3

Microwave digestion HClO4, HNO3

NRC - Microwave digestion H2O2, HNO3

- -


45

Table 2 Reference isotope for IDMS



BAM Not applicable - Pb-208, Spike isotope was Pb-207 -

IAEA Not applicable - - -

IMGC Not applicable - - -

INMETRO Not applicable - - -

IRMM Not applicable 202 - -

KRISS Not applicable 200 208 -

LGC Ltd. Not applicable 202 199 77

LNE Not applicable 200/202 - 80/82

NIST Not applicable 202 - -

NMIA Not applicable 201 206 74

NMIJ Not applicable 200/202 206/208 78/80

NRC Not applicable 201/202 - -

Table 3 Number of blends



BAM Not applicable - 4 4

IAEA Not applicable - -

IMGC Not applicable 4 4 4

INMETRO Not applicable - - -

IRMM Not applicable 8 - -

KRISS Not applicable 5 5 -

LGC Ltd. Not applicable 4 - 4

LNE Not applicable 4 - 3

NIST Not applicable - 6 6

NMIA Not applicable 4 3 -

NMIJ Not applicable - - -

NRC Not applicable - - -


46

Table 4 Experimental reproducibility



BAM 1.8 % - 1% 3.75 %

IAEA - - - -

IMGC 1.82 % - - 3.63 %

INMETRO - - - -

IRMM - 0.60% - -

KRISS - 0.38 % 2.13 % -

LGC Ltd. - 1.0 % - 3.9 %

LNE 3.7 % 1.8% - 2.7 %

NIST 0.76 % 0.47% - -

NMIA 0.37% 0.77 % 2.3 % 1.4%

NMIJ 1.4 % 1.4 % 3.0 % 0.9 %

NRC - 0.41 % - -


47

Table 5 (Isotopic) reference materials used for calibration



BAM - - NBS 981 -

IAEA - - - -

IMGC NIST SRM

1566b (Oyster Tissue)

- - NIST SRM 1566b (Oyster Tissue)

INMETRO

IAEA 393, RM 464, P 39

sample, and As and Se 100ppm

solutions traceable to NIST SRMs

- -

IAEA 393, RM 464, P 39 sample, and

As and Se 100ppm solutions traceable

to NIST SRMs

IRMM - ERM-AE640 - -

KRISS - ERM-AE640 NIST SRM991, 981 & 982 -

LGC Ltd. - in-house prepared from ORNL - in-house prepared

from ORNL

LNE As2O5 From JM, 99.9 % ERM-AE639 - AE640 -

high purity se powder JM

99.999% - spike solution

Spectrascan Se 82 ( 96.66%)

NIST - SRM 1641d - -

NMIA NIST 3103a ERM-AE640 NIST 981 NIST 3149

NMIJ residual CCQM-

P39 sample(ca.2 g)

residual CCQM-P39 sample(ca.2 g)



NRC -

198Hg enriched Me198Hg (NRCC

EOM-1) and 201Hg enriched Hg

- -


48

Table 6 Number of salmon vials used for the analysis and Use of square root of n for type A uncertainty

contributions


Participant Number of vials Sqrt (n)

BAM 2 Yes

IAEA 4 Yes

IMGC 3 Yes

INMETRO 2 Yes

IRMM 8 Yes

KRISS 5 Yes

LGC Ltd. 2 vials for Hg & Se, 2 vials for MeHg Yes

LNE 2 vials per element Yes

NIST 4 Yes

NMIA 8 Yes

NMIJ 4 Yes

NRC Two for MeHg and two for Hg Yes

49

Annex 4 – Documentation Contents


Documentation

Cover page including participants list__________________________________________

Accompanying letter_______________________________________________________

Scope of the study ________________________________________________________

General instructions _______________________________________________________

Instructions for determination of the dry-mas correction and the digestion of the Salmon _

Certification of MeHg in Salmon______________________________________________

Guidelines for result reporting _______________________________________________

Guidelines for questionnaire reporting _________________________________________

Questionnaire for measurements of Hg, Pb, Se and As ___________________________

Questionnaire for Methylmercury _____________________________________________

EUROPEAN COMMISSION DIRECTORATE GENERAL JRC JOINT RESEARCH CENTRE IRMM Insti tute for Reference Mater ials and Measurements

1st December 2004

CCQM-K43 & CCQM-P39.1 As, Hg, Pb, Se and Methylmercury in Salmon

Information Package

For further information please contact:

Dr. Y. Aregbe CCQM-K43 & CCQM-P39.1 Co-ordinator Isotope Measurement Unit tel.: +32 (0)14 571 673 fax: +32 (0)14 571 865 e-mail: [email protected]

Institute for Reference Materials and Measurements (IRMM)

European Commission – JRC Retieseweg 111, B-2440 GEEL (Belgium)

Distribution list

Registered CCQM_IAWG participants in CCQM-K43 and/or CCQM-P39.1: J. Vogl BAM E. Nadai-Fernandes CENA M. Gallorini IMGC C. Quétel IRMM P. Robouch IRMM E. Hwang KRISS R. Hearn LGC G. Labarraque LNE R. Greenberg NIST K. Inagaki NMIJ R. Sturgeon NRC J. Wang NRCCRM B. Magnusson SP L. Mackay NMIA T. Araujo INMETRO U. Sansone IAEA E. Wyse IAEA-MEL Registered invited participants to CCQM-P39.1: M. Horvat IJS E. Krupp LABEC Univ. Pau J.I. Garcia-Alonso Oviedo Univ. H. Hintelmann Trent Univ. Z. Jokai Corvinus Univ. D. Centioli APAT E. Bjorn Umea Univ. W. Hagan Frontier Geosciences Inc. CCQM and RMO delegates for info: R. Kaarls President CCQM R. Wielgosz CCQM exec. Secretary M. Sargent CCQM IAWG chairperson J. McLaren CCQM KCWG chairperson P. Charlet EUROMET METCHEM

Retieseweg 111, B-2440 Geel, Belgium Tel.: +32-(0)14-571 673 • Fax: +32-(0)14-571 865 • [email protected] • http://www.irmm.jrc.be

EUROPEAN COMMISSION DIRECTORATE GENERAL JRC JOINT RESEARCH CENTRE Institute for Reference Materials and Measurements IRMM

Geel, 1st December 2004 L/IM/94/04

To: CCQM-K43 & CCQM-P39.1 registered participants Subject: CCQM-K43 & CCQM-P39.1 “As, Hg, Pb, Se and Methylmercury in

Salmon” Dear CCQM-K43 & CCQM-P39.1 participant, As proposed, discussed and decided in previous CCQM-IAWG meetings (Paris 2004), IRMM will act as the coordinating laboratory of the CCQM-K43 key comparison and the CCQM-P39.1 pilot study, “As, Hg, Pb, Se and Methylmercury in Salmon”. The salmon material originates from Norway. The sample is a freeze dried and ground salmon muscle and skin powder bottled in amber glass vials each one containing ~ 2.2 g of material. The material is tested for stability and homogeneity. It is appropriate for the needs of this comparison. The deadline for reporting the CCQM-K43 & CCQM-P39.1 results is 31st March 2005. Subsequently the preliminary results can be presented and discussed at the CCQM-IAWG meeting in Spring, Paris. The information package for CCQM-K43 & CCQM-P39.1 includes: • This letter • Scope of the CCQM-K43 & CCQM-P39.1 pilot study • General instructions • Instructions for reporting the detailed measurement procedure including uncertainty evaluation • Instructions for the dry mass correction and digestion of the salmon • Information for CCQM-K43 & CCQM-P39.1 participants measuring methylmercury • Instructions for online result and questionnaire reporting using the IT system of IRMM

Interlaboratory comparisons If any further information is required, please do not hesitate to contact us. Yours sincerely, Dr. Y. Aregbe CCQM-K43 & CCQM-P39.1 co-ordinator IRMM, IM Unit


EUROPEAN COMMISSION DIRECTORATE GENERAL JRC JOINT RESEARCH CENTRE IRMM Insti tute for Reference Mater ials and Measurements

Geel, 1st December 2004

CCQM-K43 and CCQM-P39.1 “As, Hg, Pb, Se and Methylmercury in Salmon”

Scope of the key comparison and the pilot study

At the April meeting in Paris, 2004 it was decided to proceed the previous pilot study on tuna fish CCQM-P39, to the key comparison CCQM-K43 and the pilot study CCQM-P39.1 using a salmon material. In order to protect public health it is essential to keep contaminants at levels, which are toxicologically acceptable, thus surveillance measures were taken regarding the presence of contaminants in foodstuff, including fish. Arsenic is a mononuclidic toxic element and cannot be determined by IDMS. Rules for measurements of As are set in the commission decision on implementing council directive 96/23/EC concerning the performance of analytical methods and the interpretation of results. Including also total As measurements in these comparisons can be seen as a contribution to broaden the scope and degree of difficulty of measurements addressed by the CCQM Inorganic Working Group. Mercury is a potential environmental toxicant. The main source of human intake of mercury contaminants originates from methylmercury in fish and fishery products. Methylmercury is particularly interesting due to its high toxicity compared to inorganic mercury and its high proportion among organomercury species in the environment. Mercury species, may induce alterations in the normal development of the brain of infants and may induce neurological changes in adults. To protect public health, maximum levels of mercury in fishery products are laid down in relevant regulations. Lead may induce reduced cognitive development in children and increased blood pressure and cardiovascular diseases in adults. The EC Directive 2001/22 describes the Community methods for the sampling, the sample preparation and the analysis of Hg and Pb in fish. Very recently another EC Regulation (466/2001) was introduced that endorses officially the threshold value of 0.5 mg Hg·Kg-1 and 0.2 mg Hg·Kg-1 in salmon [1]. Selenium is an essential trace element for human beings. Seafood is an important source of Se intake for people in some regions. Certain forms of cancer and cardiovascular diseases have also been associated with Se deficiency. On the other hand Se is counted among the most important elements in terms of food-chain contamination. Se has the narrowest plateau between concentrations that show deficiency and toxic effects, respectively. Recently the European Commission has requested the Scientific Committee on Food (SCF) to review the upper level of daily intake of individual vitamins and minerals, amongst them Se, and provide the basis for the establishment of safety factors [2]. The Hg concentration in the salmon material is lower than in the tuna fish material used in CCQM-P39. The first is a real life sample with a regular Hg content for non-contaminated fish, whereas the latter was a real life sample that has been taken off the market due to its elevated Hg content. Measurements of particularly the total amount content of Hg and MeHg in this salmon material would together with the results of the CCQM-P39 pilot study on tuna fish demonstrate the measurement capabilities of the participating institutes in this important field, not only for high Hg concentrations but also for lower levels of Hg in fish. This is important in view of the fact that the threshold value in the EC Regulation (466/2001) for Hg in salmon is lower than for Hg in tuna fish.


From a metrological point of view, the measurement of the amount content of mercury in salmon is representative for many similar measurements in fish and other food matrices. Laboratories who demonstrate their capability of measuring the As, Hg, Pb and Se amount content in the CCQM-K43 and CCQM-P39.1 salmon samples, are likely to have the capability, knowledge and skills to measure the amount content of other elements at similar levels in other food matrices which require similar sample preparation. Dr. Y. Aregbe CCQM-K43 & CCQM-P39.1 co-ordinator IRMM, IM Unit 1 Commission Regulation (EC) No 466/2001 of 8 March 2001 setting maximum levels for certain contaminants in

foodstuff, Official Journal of the European Communities L077, 16/03/2001, 0001-0013

2 Guidelines of the Scientific Committee on Food for the development of tolerable upper intake levels for vitamins, minerals and trace elements SCF/CS/NUT/UPPLEV/11 Final, Nov/2000


EUROPEAN COMMISSION DIRECTORATE GENERAL JRC JOINT RESEARCH CENTRE IRMM Inst i tute for Reference Mater ials and Measurements


CCQM-K43 & CCQM-P39.1

As, Hg, Pb, Se and Methylmercury in Salmon

General instructions and guidelines

♦ Each participant will receive 4 salmon samples. On arrival, it is recommended to store the glass vials containing the salmon material refrigerated at 4 oC.

♦ Please can you forward me confirmation the day of delivery, confirming the condition of the vials received to the following email address [email protected]

♦ The amount contents of Hg, Pb and MeHg in the salmon are approximately in the range of 0.1 - 5 µmol · Kg-1 and for As and Se approximately 5 - 50 µmol · Kg-1

♦ To account for the small unit size, each participant will receive 4 bottles (8-10g) of the salmon material where at least 2 sample aliquots from 2 bottles must be analysed for each measured analyte. In view of the limited number of salmon samples and the small unit size available, please plan carefully your measurements as far as the amount of sample needed is concerned.

♦ The participant is free to choose the analytical procedure for measurements in the salmon sample provided it is fit for purpose.

♦ Since the majority of the laboratories participating in CCQM-K43 & CCQM-P39.1 will use IDMS, a few specific points for this analytical method are highlighted although most of the participants have considerable experience in isotope dilution measurements.

• minimise contamination (work in closed systems or class 100 clean bench, check

reagents and lab ware used) • prepare the blends and dilutions gravimetrically. Avoid weighing of too small

aliquots of solids or liquids in order to minimise the weighing uncertainty. • correct sample weighing for dry mass (see specific instructions) • spike the salmon prior to the digestion • make sure that the salmon digestion is complete (see specific instructions) • possible isobaric interferences for the As, Hg, Pb and Se isotopes should be

investigated and treated accordingly • the correction factors for mass discrimination in the ratio measurements should be

measured repeatedly using materials of known isotopic composition and ratios similar to those in the blends or samples

• participants measuring MeHg, please consult the attached information letter “certification of MeHg in salmon”


Instructions for result reporting and uncertainty evaluation ♦ For the first time registration and result/questionnaire reporting is done online via the IT

system of IRMM interlaboratory comparisons. Please report your results and questionnaire replies according to the guidelines .

♦ The uncertainty statement should be evaluated and presented according to the principles outlined in, e.g. “ISO/GUM” [1] or the Eurachem/CITAC Guide [2]. This implies that you 1) state your measurement equation 2) identify all significant sources of uncertainty 3) state your input quantities 4) include factors related to sample treatment in your measurement equations 5) describe the applied evaluation process and type of assumed distribution for your uncertainty estimation 6) quantify uncertainty components and convert them to standard uncertainties 7) calculate the combined standard uncertainty uc 8) present an expanded uncertainty U with the coverage factor k=2

♦ As our IT system is still in developing production phase II it is not possible yet to attach documents to your individual result report sites. Therefore the description of the measurement procedure and the sample pre-treatment including the complete uncertainty statement needs to be sent as attachment by email to [email protected]

♦ The whole information package including guidelines for result reporting will also be sent to you via email.

If you require further information or assistance, do not hesitate to contact us. Please address directly Dr. Christophe Quétel ([email protected]) in case you need more specific information related to the MeHg measurements. Dr. Y. Aregbe CCQM-K43 & CCQM-P39.1 co-ordinator IRMM, IM Unit 1. International Organisation for Standardisation, “Guide to the Expression of Uncertainty in Measurement”,

©ISO, ISBN 92-67-10188-9, Geneva, Switzerland, 1993.

2. Eurachem/CITAC Guide Quantifying uncertainty in analytical measurement (2nd ed. 2000), www.eurachem.bam.de.


EUROPEAN COMMISSION DIRECTORATE GENERAL JRC JOINT RESEARCH CENTRE IRMM Inst i tute for Reference Mater ials and Measurements


Instructions for determination of the dry-mass correction and the digestion

of the salmon sample in CCQM-K43 & CCQM-P39.1

There are two potential problems in measurements performed on matrices like the salmon material used in these comparisons. Firstly, and most important, the water content of the powdered salmon will affect the salmon mass, and a correction for that is needed. From recent work in that area [1, 2] it seems that this correction is very important because depending on the method used a different result can be obtained. This means that the “measurand” is to some extent “operationally defined”. In order to achieve comparability of results the protocol as given below, must be followed by the CCQM-K43 & CCQM-P39.1 participants. Secondly, the digestion of the salmon material (if needed for the procedure that you are following) is never a trivial exercise. This document intends to give guidance on the above matters. 1. Dry-mass correction The salmon will absorb ambient moisture at typical laboratory temperature and humidity conditions. Therefore the sample bottle should only be opened immediately before weighing aliquots for the IDMS blend preparation. For correction of the measured values to dry mass, water content measurements should be made on a separate portion of the same material with a mass of 0.6 ± 0.1g. The material should be dried before weighing for a minimum of 24 hours in a ventilated oven at 102 ± 2 oC. Cycles of drying and weighing should be repeated until a constant mass is attained. Each weighing has to be carried out after the sample has reached thermal equilibrium at room temperature in a desiccator, recommended time about 30 min. Successive weights should not differ more than 0.001 g. The loss of mass corresponds to the “dry-mass correction factor” that should be applied. 2. Digestion of the salmon (only in case the method used requires digestion) There are a variety of digestion methods, employing various combinations of acids and for which different instruments are used. • use minimum sample mass of 0.4 g. • aim is to digest the salmon material completely. • should this fail, As, Hg, Pb and Se content in the residue should be measured in order to

estimate the correction needed and its uncertainty contribution. If you require any further assistance or information, please do not hesitate to contact us. Dr. Y. Aregbe CCQM-K43 & CCQM-P39.1 co-ordinator IRMM, IM Unit 1. S. Rückold et. al. Water as a source of errors in reference materials,

Fresenius J Anal Chem (2001) 370: 189 - 193


2. S. Rückold et. al. Determination of the contents of water and moisture in milk powder, Fresenius J Anal Chem

(2000) 368: 522 - 527

Retieseweg 111, B-2440 Geel, Belgium Tel.: +32-(0)14-571 658 • Fax: +32-(0)14-571 673 • e-mail: [email protected] • http://www.irmm.jrc.be

EUROPEAN COMMISSION DIRECTORATE GENERAL JRC JOINT RESEARCH CENTRE Institute for Reference Materials and Measurements IRMM


CCQM-K43 & CCQM-P39.1 Certification of MeHg in Salmon

Dear colleague,

You have registered for the CCQM-K43 & CCQM-P39.1 interlaboratory comparisons on on the determination of the MeHg amount content in salmon. In total, there will be 16 participants including 9 from CCQM and 7 invited experts measuring MeHg. Since you have participated in the previous pilot study on tuna fish you have already received the IRMM-670 202Hg enriched MeHg isotopic CRM. The use of the IRMM-670 solution is intended to help you applying the isotope dilution mass spectrometry (IDMS) method for the determination of the MeHg content in the salmon sample. However, the use of IRMM-670 is only recommended and is by no means mandatory. It is expected that the participants will provide experimental results according to one of the 5 approaches described below. 1- Apply a direct IDMS (equation 1) approach using the 202Hg enriched MeHg IRMM-670 as a spike solution. 2- Apply a double IDMS (equation 2) approach using the 202Hg enriched MeHg IRMM-670 as a spike solution

(and thus chose to re-characterise it). 3- Apply another method than the two above. Equation 1.

Equation 2.

Considering that the characterisation of the MeHg content in the IDMS spike material is a crucial step, we invite the ‘IDMS participants’ to apply scenario 1, to make maximum use of the of IRMM-670 solution. In this way the number of potential sources of measurement biases among participants’ results can be minimised. At the same time, applying scenario 1 facilitates the final interpretation of possibly occurring significant differences between the participants’ results. Again, it is emphasised that the participants should remain entirely free to apply the scenario they like best and/or judge most appropriate.

Yours sincerely,

Dr. Christophe Quétel Isotope Measurements Unit EC-JRC-IRMM

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Retieseweg 111, B-2440 Geel, Belgium Page 1 Tel.: +32-(0)14-571 673 • Fax: +32-(0)14-571 865 • [email protected] • http://www.irmm.jrc.be• http://www.imep.ws

GUIDELINES to Participants on Reporting Results for CCQM-K43.

Our result reporting pages will only be open from the end of January 2005, we will notify you by e-mail when these pages are available. These guidelines will explain how you can report your measurement result and uncertainty. Further guidelines on how to complete the questionnaire information will be attached in the above mentioned e-mail. Participant’s name «SURNAME» Your password key: «PARTKEY» Sample 1 code no.: «SAMPLECODE»«Next Record» Sample 2 code no: «SAMPLECODE»«Next Record» Sample 3 code no: «SAMPLECODE»«Next Record» Sample 4 code no: «SAMPLECODE»«Next Record» Amount content code no: «SAMPLECODE» The result reporting is done on the Internet, the login page is located using the following URL http://www.irmm.jrc.be/imepapp/jsp/loginResult.jsp The following information page will appear. To obtain the login page, close down this screen.


This is the login page.

Please use your allocated password key

EXAMPLE:- Password Key – AYII1892393 Your Password Key – «PARTKEY» Once you have entered your password key, press the SUBMIT button (Please note that your password key is unique to the comparison you have registered to.) The RESULT REPORT FORM

Completing the RESULT REPORTING Page. 1. Please make sure that the correct result is entered for the correct sample code and for the correct analyte. In case you don’t measure all the samples or all the analytes, please leave the corresponding fields blank. Please be aware that for each analyte at least 2 replicates from 2 bottles have to be measured. 2. Indicated on the top right hand side of the screen, shows how many pages there are.


Page 1 to 5. Per page displays the same sample code and the list of analytes. 3. For each analyte by sample code there are 2 replicates measurements: MEASUREMENT #1 and MEASUREMENT #2 Please ONLY enter information in the result field. (Leave the uncertainty and the coverage factor fields blank) Detailed information on the replicates measured needs to be included in the description of the measurement procedure that has to be sent as an attachment by email. (See also “instructions for result reporting and uncertainty evaluation”) 4. The measurement unit field has already been set. 5. In the field marked “Result value” enter your measurement result using the 2nd box to your left. 6. Select the field marked “Technique used” this will activate the drop down menu. Select the technique used. If the technique used is not listed, select the “OTHER” field and then specify When the “Technique used” field has been selected the “OTHER” field is disabled and no input can be entered. Likewise should you select the “OTHER” field then the “Technique used” field is disabled. 7. When completing the AMOUNT CONTENT on page five, in the field with your code no. «SAMPLECODE», you are required to complete ALL fields. RESULT, UNCERTAINTY and COVERAGE FACTOR. This is the overall result per analyte. Below is an example of a completed result screen for one sample and one analyte.

Once you have completed the first screen to proceed to the following screen, FIRST press the SAVE button followed by the NEXT.


SAVE – The SAVE button stores the entered data with the possibly to edit them as often as you need. To reconnect to our system use the same URL link http://www.irmm.jrc.be/imepapp/jsp/loginResult.jsp and re-supply your password key. The result form will appear with the data that has already been entered. Make the required changes and select the SAVE button. This pop up page will appear advising you that your results have been saved.

The SUBMIT button is located at the button of each page, ONLY press this button when you have entered all you data. How to SUMBIT your results Once the SUBMIT button has been pressed, the questionnaire will appear ready for your input. Guidelines on how to complete the questionnaire information will follow shortly by e-mail. Remember to submit your results before the deadline date, as ONLY submitted results will be accepted.


GUIDELINES to Participants on completing the Questionnaire for CCQM-K43 and CCQM-P39.1.

Once you have entered your results and pressed the SUBMIT button, the questionnaire information will appear ready for your input. The QUESTIONNAIRE FORM Completing the QUESTIONNAIRE Page. 1. You must enter or select data to every question, otherwise your questionnaire information will not be submitted. Should you not complete a question, or complete a question incorrectly, a message will appear directing you to that relevant question. IF YOU HAVE LEFT A QUESTION BLANK, WHERE AN ANSWER IS REQUESTED, YOU WILL RECEIVE AN ERROR MESSAGE, IF YOU HAVE NO COMMENTS RELATING TO THAT QUESTION, PLEASE CAN WE REQUEST THAT YOU INPUT ‘NOT APPLICABLE’. (PLEASE USE THE FOLLOWING FORMAT N/A) 2. Text fields are a maximum of 150 characters. 3. QUESTION 1 to 8 should be answered by all participants. QUESTION 9 to 17 should ONLY be answered if a measurement has been done for METHYLMERCURY, if no measurement has been done, please select for EACH question the option – ‘CH3Hg non Applicable measurement’ 4. Instructions for question no.10 PART A If you have selected ‘CH3Hg Applicable measurement for this question, you are now requested to select one of the three approaches listed. If selecting approach 3 (Approach 3 – another method than species specific IDMS) then you will need to select one of the three sub-questions in PART B.

ONLY WHEN SELECTING APPROACH 3 and OTHER, in PART B will question no. 11 need to be answered. Otherwise select ‘CH3Hg non Applicable measurement’

Part A

Part B


5. Instructions for question no.11 When PART A = approach 3 and PART B = OTHER, have been chosen. Please select ‘CH3Hg Applicable measurement’ and specify the used calibration strategy.

6. Instructions for question no.12 ONLY WHEN SELECTING APPROACH 3 and CALIBRATION WITH EXTERNAL MATRIX MATCHED STANDARDS, in PART B of question no.10, requires you to answer question no.12. Otherwise select ‘CH3Hg non Applicable measurement’

7. Instructions for question no.13 When PART A = approach 2 has been chosen in question no.10. Please select ‘CH3Hg Applicable measurement’ and specify your results for the determination of the MeHg content. Otherwise select ‘CH3Hg non Applicable measurement’ 8.Instructions for question no.15 When in PART A = approach 1 OR 2 has been chosen in question no.10. Please select ‘CH3Hg Applicable measurement’ and answer the next two questions with your comments. Otherwise select ‘CH3Hg non Applicable measurement’ Once you have completed the questionnaire, press the SUBMIT QUESTIONNAIRE button.


If you answered a question in the wrong format, or left a question blank, you will receive an error message, the system will direct you to that relevant question by adding a message in red text. Below is an example of an error message screen.

Before re-submitting your data, please make sure that the following has been applied:-

a) Ensure all questions have been completed. b) Ensure that the comment field has only been completed when asked.

When the requested changes have been made, press the SUMBIT QUESTIONNAIRE button again. If entries are acceptable by the system, the following confirmation screen will appear showing all the data entered.


Should any amendments need to be made, press the CHANGE RESULTS AND QUESTIONNAIRE button, this will return you to the previous screen. Make the required changes and submit your data again. Once again, the confirmation screen will appear, check your data again. When all data is correct, press the CONFIRM RESULTS AND QUESTIONNAIRE button. (Located at the bottom of the screen)

It is IMPORTANT that you print off your result report form, from the available print option. Please sign and fax this document to IRMM on Fax No. +32 (0)14 571 865


The final screen will conclude that your data has been accepted by IRMM, this message will appear at the top of the screen.

IMPORTANT : Disclaimer, Confidentiality Notice and rules on Privacy Protection IRMM Interlaboratory Comparison

> Login > Results > Questionnaire

Functions Results

Questionnaire for CCQM-K43

Dr. Yetunde Aregbe IRMM BELGIUM

1. Salmon moisture content

What was the moisture content by % of the weighed sample?

What was the uncertainty of the moisture content by % of the weighed sample?

2. Applied correction factor for dry-mass

What was the applied correction factor for dry-mass?

What was the uncertainty of the applied correction factor for dry-mass?

3. Which reference isotope was used (for IDMS)?

4. What was the number of blends (for IDMS)?

5. What was the number of vials from which the salmon was analysed?

6. Was the square root of n used for type A uncertainty contributions? Yes No 7. What was the experimental reproducibility of Cx from different sample aliquots in % (blends

standard deviation and NOT the standard deviation of the mean)?

8. Which (isotopic) reference materials were used for calibration purposes?

9. Moisture content for Methylmercury measurements CH3Hg Applicable measurement CH3Hg non Applicable measurement

What was the moisture content by % of the weighed sample?

What was the uncertainty of the moisture content by % of the weighed sample?

10.Measurement strategy? CH3Hg Applicable measurement CH3Hg non Applicable measurement

Page 1 of 3IRMM Interlaboratory Comparison

16/12/2005http://www.irmm.jrc.be/imepapp/result.action

Approach 1:direct IDMS with 202Hg enriched

MeHg ERM-AE670 as a spike solution

Approach 2:double IDMS with 202Hg enriched MeHg ERM-AE670 as a spike

solution (re-characterization of ERM-AE670)

If CH3Hg applicable measurement which measurement strategy was used?

Yes

If Approach 3, Calibration with external matrix matched standards

If Approach 3, Method of standard addition (SA) calibration

If Approach 3, Other

11.Measurement strategy continued CH3Hg Applicable measurement CH3Hg non Applicable measurement

If Approach 3 and Other is applicable, please specify the used calibration strategy

12.Internal standard? CH3Hg Applicable measurement CH3Hg non Applicable measurement

If Approach 3 and Calibration with external matrix standard was applied with an internal standard,internal standard used

13.MeHg content? CH3Hg Applicable measurement CH3Hg non Applicable measurement

In case Approach 2, was applied, please report your results for the determination of the MeHg conusing your own values for the ERM-AE 670 solution and using the values provided by IRMM for thsolution MeHg amount content (mol(CH3Hg).kg-1) obtained using own values for the ERM-AE670 solution

Uncertainty (k=2) (mol(CH3Hg).kg-1) obtained using own values for the ERM-AE670 solution

MeHg amount content (mol(CH3Hg).kg-1) obtained using the IRMM values for the ERM-AE670 so

Uncertainty (k=2) (mol(CH3Hg).kg-1) obtained using the IRMM values for the ERM-AE670 solutio

14.Measurement strategy based on SA or ID CH3Hg Applicable measurement CH3Hg non Applicable measurement

Some hours prior

to MeHg extraction

Immediately prior to MeHg

extraction

Aftprio

If a measurement strategy based on SA or ID was used which of the following options most closely fits the timing of the spike addition in your method?

15.Measurement strategy involving species specific IDMS Approaches 1 and 2 CH3Hg Applicable measurement CH3Hg non Applicable measurement

If the measurement strategy involved species specific IDMS Approaches 1 and 2, (as described inplease answer the following questions Reference isotope used during the measurements

Number of replicate blend samples prepared



16.Measurement process CH3Hg Applicable measurement CH3Hg non Applicable measurement

Please describe briefly your measurement process by listing the types of reagents and apparatus extraction and derivatisation of MeHg in the sample Sample mass (g)

Extraction reagents (e.g. HCl, TMAH etc.)

Extraction apparatus (e.g. microwave, ultrasound bath etc.)

Derivatisation reagents (e.g. NaB(C2H5)4, Grignard etc.)

Species separation apparatus (e.g. GC, LC, column type, carrier)

Detector (e.g. CVAAS, ICP-MS etc.)

17.Experimental reproducibility CH3Hg Applicable measurement CH3Hg non Applicable measurement

What was the reproducibility of Cx from the different sample aliquots measured in % (blends in castandard deviation and NOT the standard deviation of the mean)

Clear

Submit questionnaire

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Documents

CCQM-K43 final report - BIPM · December 2005 CCQM-K43 As, Hg, Pb, Se and Methylmercury in Salmon FINAL REPORT Y. Aregbe and P.D.P. Taylor With contributions from: J. Vogl and A