Analytical methods

Analytical methods used by the participating in this ILC laboratories are presented on Figure 5. Generally, they can be divided to three groups: nondestructive techniques (NAA, XRF);

plasma spectrometric methods (ICP-MS and ICP-OES) and atomic absorption spectrometry methods, representing 10%, 60% and 20% respectively. Abbreviation used in the figure 5 and appendix II are shown in Table 6.

FIG. 5. Graphical distribution of instrumental techniques.

TABLE 6. ABBREVIATIONS OF INSTRUMENTAL TECHNIQUES USED IN THE

ICP-MS Inductively Coupled Plasma Mass Spectrometry

ICP-OES Inductively Coupled Plasma Optical Emission Spectrometry

NAA Neutron Activation Analysis

XRF X-Ray Fluorescence Spectrometry

13 5.4 SAMPLE TREATMENT, IMPACT OF WATER CONTENT, USE OF CRM AND

RECOVERY CORRECTIONS

Eleven participants (22%) didn’t report the obtained for the CRM results as requested in the reporting form. Eight participating laboratories didn’t provide QC results for all requested elements. An important principle for the selection of reference material by laboratories was the principle of matrix and concentration range matching. CRMs used in this ILC were appropriately selected as most of laboratories used biota matrices of marine origin (i.e. IAEA 407 Tuna fish and IAEA 461 Clam from the IAEA, SRM 2976 mussel from the NIST).

Sixteen participants (32%) claimed to be accredited, but only part of them were accredited for the determination of trace element in fish sample matrix. 4 participants (25%) from accredited laboratories didn’t report results for QC sample. In general, results reported by accredited laboratories were comparable with results reported by non-accredited laboratories. Only one of accredited laboratory (6%) and 6 of non-accredited laboratories (36%) reported 100% of their results with │z│ ≤ 2.

Only 6 laboratories (12%) claimed implementing correction for recovery for at least part of their reported results, but 25 participants didn’t provide results for recoveries. Most of recoveries reported were in the range of 100 ± 25%. High proportion of the laboratories that didn’t perform correction for recovery have obtained satisfactory scorings, meaning that the laboratories have correctly estimated that the recovery achieved was not significantly different from 100%.

The ILC fish sample was subjected to freeze drying as part of its preparation process. At the time of bottling, the moisture content of the material was around 6.5%. Depending on local storage conditions and humidity levels the ILC sample might absorb moisture from the environment. Consequently, users were advised to make a separate determination of the moisture content of the material. As the moisture is operationally dependent parameter [5]

procedure on moisture content determination in the test sample was provided to all participating laboratories in the accompanying letter. Only 27 participants (55%) claimed to report results corrected for moisture, 14 of them have used effectively the prescribed by the organizers protocol (85°C). Other 13 laboratories didn’t provide their methodology for moisture determination. Inadequate determination of moisture can be a source of bias, especially for biological matrices, where the moisture content is often more than 5%. The moisture content reported by the laboratories that applied a correction factor was in the range from 0.05 to 11%.

It should be noted that out of 49 data sets received, 12 participants didn’t fill the questionnaire as requested.

6 RECOMMENDATIONS

Participants are recommended to review their data element by element, appraising whether the

z-scores and Zeta-scores are less than or equal to 2. The use of z-scores and Zeta-scores will

help to identify systematic errors in the measurement results (e.g. from calibration, reagent contamination or incomplete digestion) and should ultimately improve data quality.

Laboratories should investigate all unsatisfactory scores (i.e. |z| or |Zeta| > 3) and put in place

the necessary corrective actions in order to prevent the problem reoccurring. This is also a

requirement for accredited according to the ISO/IEC 17025 standard laboratories. [6].

14

Participants reporting total mercury in fish sample are strongly suggested to look at the implementation of methodologies for the measurement of mercury speciation’s, when the obtained measurement results are used for risk assessment purposes.

Some laboratories still need to improve quality assurance / quality control procedures, to implement regular analysis of certified reference materials and the use of quality control chart in their daily laboratory practice. This way of work provides continuous feedback to the analyst and is an essential tool for the monitoring of data quality and for the production of reliable measurement results, used in the monitoring and risk assessment studies.

A full catalogue of available IAEA reference materials is published regularly and can be consulted on the IAEA website: http://www.iaea.org/programmes/aqcs.

7 CONCLUSIONS

Although the overall performance of participating in this ILC laboratories is quite satisfactory, it must be pointed that for elements present at low to ultra-low concentration levels (i.e Cd, Pb) in fish matrix, there is clear danger of contamination problems. It is a subject of concern as these elements are toxics and the accurate determination of their content in seafood is of crucial importance.

The implementation of Minamata convention, especially article 19, should lead to increasing number of laboratories involved in the monitoring of mercury but also on mercury species, especially in fish samples. The need for improvement in this analytical field is obvious, as only 12% of participants in the ILC are in a position to report obtained measurement results for CH

3

Hg.

An extra effort is needed for relevant evaluation of measurement uncertainties, associated with measurement results. There is still almost 20% of participants that do not report results with associated uncertainties. As a result, the number of unsatisfactory Zeta-scores was systematically higher than the number of unsatisfactory z-scores for the same trace elements.

The uncertainty associated with measurement results is of paramount importance in the frame of different regulations and international agreements, and it is important for any analytical laboratory to report a complete uncertainty statement.

In general, it should be noted that uncertainty evaluations based only on the precision of

measurement results are very often underestimated. In many cases, they do not include other

major contributors, coming from uncertainties on the determination of recovery, procedural

blank, moisture content etc.

15 APPENDIX I

PERFORMANCE EVALUATION BY ELEMENT IN

IAEA-MESL-ILC-TE-BIOTA-2017

16

Evaluation of Reported data for Ag

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 59% 0% 41%

Zeta-score 46% 23% 31%

Xass: 0.066 mg kg^-1

Uass (k=2): 0.008 mg kg^-1

2p: 0.017 mg kg^-1

Number of results: 17

Number of method: 3

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

17 Evaluation of Reported data for As

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 87% 10% 3%

Zeta-score 69% 8% 23%

Xass: 19.9 mg kg^-1

Uass (k=2): 1.1 mg kg^-1

2p: 5.0 mg kg^-1

Number of results: 30

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

18

Evaluation of Reported data for Ca

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 90% 0% 10%

Zeta-score 84% 8% 8%

Xass: 27.5 × 10³ mg kg^-1

Uass (k=2) : 4.6 × 10³ mg kg^-1

2p: 6.8 × 10³ mg kg^-1

Number of results: 25

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

19 Evaluation of Reported data for Cd

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 64% 6% 31%

Zeta-score 65% 13% 23%

Xass: 0.032 mg kg^-1

Uass (k=2) : 0.004 mg kg^-1

2p: 0.008 mg kg^-1

Number of results: 36

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

20

Evaluation of Reported data for Co

Kernel density Plot

Summary of results:

Xinfo: 0.121 mg kg^-1

Uinfo (k=2) : 0.020 mg kg^-1

2p: 0.030 mg kg^-1

Number of results: 24

Number of method: 5

Reported results and expanded uncertainties:

___ X_info ; X_lab ± U_lab; ---- X_info± 2_p ;---- X_info± U_info(k=2)

21 Evaluation of Reported data for Cr

Kernel density Plot

Summary of results:

Xinfo: 3.45 mg kg^-1

Uinfo (k=2) : 0.86 mg kg^-1

2p: 0.86 mg kg^-1

Number of results: 34

Number of method: 6

Reported results and expanded uncertainties:

___ X_info ; X_lab ± U_lab; ---- X_info± 2_p ;---- X_info± U_info(k=2)

22

Evaluation of Reported data for Cu

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 69% 13% 18%

Zeta-score 64% 9% 27%

Xass: 2.40 mg kg^-1

Uass (k=2) : 0.34 mg kg^-1

2p: 0.60 mg kg^-1

Number of results: 39

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

23 Evaluation of Reported data for Fe

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 87% 10% 3%

Zeta-score 76% 12% 12%

Xass: 138 mg kg^-1

Uass (k=2) : 19 mg kg^-1

2p: 35 mg kg^-1

Number of results: 39

Number of method: 7

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

24

Evaluation of Reported data for Hg

Kernel density Plot Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 89% 0% 11%

Zeta-score 61% 21% 18%

Xass: 0.593 mg kg^-1

Uass (k=2) : 0.032 mg kg^-1

2p: 0.148 mg kg^-1

Number of results: 35

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

25 Evaluation of Reported data for K

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 89% 0% 11%

Zeta-score 88% 0% 12%

Xass: 14.0 × 10³ mg kg^-1

Uass (k=2) : 2.4 × 10³ mg kg^-1

2p: 3.5 × 10³ mg kg^-1

Number of results: 28

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

26

Evaluation of Reported data for CH

3

Hg

Kernel density Plot

< 8 results

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 67% 0% 33%

Zeta-score 60% 0% 40%

Xass: 0.531 mg kg^-1 as Hg

Uass (k=2) : 0.092 mg kg^-1 as Hg

2p: 0.133 mg kg^-1 as Hg

Number of results: 6

Number of method: 3

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

27 Evaluation of Reported data for Mg

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 85% 4% 11%

Zeta-score 82% 9% 9%

Xass: 2.11 × 10³ mg kg^-1

Uass (k=2) : 0.37 × 10³ mg kg^-1

2p: 0.53 × 10³ mg kg^-1

Number of results: 27

Number of method: 7

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

28

Evaluation of Reported data for Mn

Kernel density Plot

Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 89% 5% 5%

Zeta-score 77% 10% 13%

Xass: 15.4 × 10³ mg kg^-1

Uass (k=2) : 1.5 × 10³ mg kg^-1

2p: 3.9 × 10³ mg kg^-1

Number of results: 37

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

29 Evaluation of Reported data for Ni

Kernel density Plot

Summary of results:

Xinfo: 4.09 mg kg^-1

Uinfo (k=2) : 1.18 mg kg^-1

2p: 1.02 mg kg^-1

Number of results: 34

Number of method: 6

Reported results and expanded uncertainties:

___ X_info ; X_lab ± U_lab; ---- X_info± 2_p ;---- X_info± U_info(k=2)

30

Evaluation of Reported data for Pb

Kernel density Plot Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 64% 11% 25%

Zeta-score 53% 13% 33%

Xass: 0.606 mg kg^-1

Uass (k=2) : 0.064 mg kg^-1

2p: 0.152 mg kg^-1

Number of results: 36

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

31 Evaluation of Reported data for Se

Kernel density Plot Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 92% 4% 4%

Zeta-score 86% 0% 14%

Xass: 2.17 mg kg^-1

Uass (k=2) : 0.20 mg kg^-1

2p: 0.54 mg kg^-1

Number of results: 25

Number of method: 4

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

32

Evaluation of Reported data for Sn

Kernel density Plot Summary of results:

Xinfo: 0.182 mg kg^-1

Uinfo (k=2) : 0.054 mg kg^-1

2p: 0.045 mg kg^-1

Number of results: 12

Number of method: 2

Reported results and expanded uncertainties:

___ X_info ; X_lab ± U_lab; ---- X_info± 2_p ;---- X_info± U_info(k=2)

33 Evaluation of Reported data for Sr

Kernel density Plot Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 92% 4% 4%

Zeta-score 90% 0% 10%

Xass: 136 mg kg^-1

Uass (k=2) : 23 mg kg^-1

2p: 34 mg kg^-1

Number of results: 23

Number of method: 4

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

34

Evaluation of Reported data for V

Kernel density Plot Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 50% 31% 19%

Zeta-score 46% 31% 23%

Xass: 0.405 mg kg^-1

Uass (k=2) : 0.085 mg kg^-1

2p: 0.101 mg kg^-1

Number of results: 16

Number of method: 4

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

35 Evaluation of Reported data for Zn

Kernel density Plot Summary of results:

Satisfactory Questionable Unsatisfactory

z-score 93% 0% 8%

Zeta-score 65% 15% 21%

Xass: 52.1 mg kg^-1

Uass (k=2) : 3.0 mg kg^-1

2p: 13.0 mg kg^-1

Number of results: 40

Number of method: 6

Reported results and expanded uncertainties:

Performance evaluation:

z-score Zeta-score

___ X_ass ; X_lab ± U_lab; ---- X_ass± 2_p ;---- X_ass± U_ass(k=2)

APPENDIX II

REPORTED RESULTS BY PARTICIPANTS

38

TABLE 7. REPORTED RESULTS BY PARTICPANTS Lab codeAnalyteUnit Instrumental MethodLab MeanLab U kz-score Zeta-score QC 2 Agmg kg-1 ICP-MS0.0700.0422 0.530.20No QC Reported 10Agmg kg-1 ICP-MS0.1000.0302 4.122.19na 16Agmg kg-1 ICP-MS0.1850.1102 14.462.16DOLT 2 20Agmg kg-1 Neutron Activation0.5500.0301 58.6716.0NIST 1566b 21Agmg kg-1 ICP-OES0.0570.0072 -1.04-1.57IAEA 407 25Agmg kg-1 ICP-MS0.0700.48NIST 2976 28Agmg kg-1 ICP-MS0.0330.0202 -3.96-3.03No QC Reported 31Agmg kg-1 ICP-MS0.0670.0062 0.160.27IAEA 407 35Agmg kg-1 ICP-MS0.0560.0032 -1.21-2.16No QC Reported 36Agmg kg-1 ICP-MS0.053-1.64TORT 42Agmg kg-1 ICP-MS0.0720.0281.960.690.39IAEA 407 43Agmg kg-1 ICP-OES0.1070.0042 4.939.09No QC Reported 53Agmg kg-1 ICP-OES0.2500.0602 22.306.08No QC Reported 55Agmg kg-1 ICP-MS0.76784.93No QC Reported 57Agmg kg-1 ICP-MS0.058-0.95DORM 4 58Agmg kg-1 ICP-MS0.0580.0062 -1.01-1.67NIST 2976 59Agmg kg-1 ICP-MS0.0590.0122 -0.81-0.92IAEA 461 5 Asmg kg-1 Neutron Activation20.00.92 0.030.11SRM 1566b 6 Asmg kg-1 ICP-MS20.51.02 0.250.83No QC Reported 10Asmg kg-1 ICP-MS19.65.32 -0.13-0.12TORT 3

39 TABLE 7. REPORTED RESULTS BY PARTICPANTS (cont.) Lab codeAnalyteUnit Instrumental MethodLab MeanLab U kz-score Zeta-score QC 11Asmg kg-1 ICP-MS21.13.22 0.480.71CUSTOM 12Asmg kg-1 Hydride AAS16.70.82 -1.28-4.59IAEA 461 13Asmg kg-1 ICP-MS21.11.42 0.481.32NIST 2976 14Asmg kg-1 ICP-MS21.31.22 0.581.74DORM 4 15Asmg kg-1 XRF 19.71.72 -0.07-0.16NIST 2976 20Asmg kg-1 Neutron Activation16.90.51 -1.20-3.83NIST 1566b 21Asmg kg-1 ICP-OES13.71.22 -2.51-7.75IAEA 407 22Asmg kg-1 Graphite Furnace AAS 14.20.52 -2.31-9.38DORM 4 23Asmg kg-1 ICP-MS19.73.42 -0.06-0.09No QC Reported 25Asmg kg-1 ICP-MS19.7-0.07NIST 2976 28Asmg kg-1 Neutron Activation18.80.32 -0.43-1.83NIST 1566b 31Asmg kg-1 ICP-MS20.11.72 0.090.23IAEA 407 35Asmg kg-1 ICP-MS25.71.22 2.325.85No QC Reported 36Asmg kg-1 ICP-MS20.10.08TORT 42Asmg kg-1 ICP-MS19.10.91.96-0.32-1.10IAEA 407 43Asmg kg-1 ICP-OES20.710.02 0.310.15No QC Reported 45Asmg kg-1 XRF 18.72.02 -0.50-1.08No QC Reported 46Asmg kg-1 ICP-MS20.010.02 0.040.02No QC Reported 47Asmg kg-1 Hydride AAS21.26.40.540.41DORM 4 49Asmg kg-1 ICP-OES18.23.0-0.68-1.06TORT 3

40

TABLE 7. REPORTED RESULTS BY PARTICPANTS (cont.) Lab codeAnalyteUnit Instrumental MethodLab MeanLab U kz-score Zeta-score QC 53Asmg kg-1 ICP-OES66.08.12 18.5111.2No QC Reported 54Asmg kg-1 Hydride AAS21.10.30.472.01IAEA 407 55Asmg kg-1 ICP-MS20.70.34No QC Reported 57Asmg kg-1 ICP-MS22.40.99DORM 4 58Asmg kg-1 ICP-MS19.20.42 -0.27-1.12NIST 2976 59Asmg kg-1 ICP-MS23.34.02 1.351.62IAEA 461 60Asmg kg-1 Graphite Furnace AAS 15.63.92.21-1.74-2.14IAEA 407 1 Ca mg kg-1 Flame AAS12823-4.26No QC Reported 2 Ca mg kg-1 Flame AAS1518730372 -3.57-4.41No QC Reported 5 Ca mg kg-1 Neutron Activation254637002 -0.58-0.84SRM 1515 6 Ca mg kg-1 ICP-OES3019336802 0.800.93No QC Reported 10Ca mg kg-1 ICP-MS29567125102 0.620.32No QC Reported 11Ca mg kg-1 ICP-MS2976753002 0.680.66NIST 1547 12Ca mg kg-1 Flame AAS2967314082 0.650.91IAEA 461 13Ca mg kg-1 ICP-MS3037322472 0.851.13NIST 2976 15Ca mg kg-1 XRF 226036072 -1.41-2.06IAEA 413 19Ca mg kg-1 ICP-OES292309202 0.520.75NIST SRM 1566a 20Ca mg kg-1 Neutron Activation256097661 -0.54-0.75NIST 1566b 23Ca mg kg-1 ICP-MS2859028602 0.330.42No QC Reported 26Ca mg kg-1 POLAROGRAPHY4330 2 -7.87-11.6IAEA 407

41 TABLE 7. REPORTED RESULTS BY PARTICPANTS (cont.) Lab codeAnalyteUnit Instrumental MethodLab MeanLab U kz-score Zeta-score QC 27Ca mg kg-1 Flame AAS2546535262 -0.58-0.68IAEA 407 28Ca mg kg-1 Neutron Activation2913721802 0.490.66NIST 1566b 30Ca mg kg-1 ICP-OES226352264-1.40-1.86No QC Reported 31Ca mg kg-1 ICP-OES2872524422 0.370.49IAEA 407 35Ca mg kg-1 ICP-OES259583932 -0.43-0.64No QC Reported 36Ca mg kg-1 ICP-MS26597-0.25Skimmed Milk Powder 43Ca mg kg-1 ICP-OES33333100002 1.721.07No QC Reported 45Ca mg kg-1 XRF 339071802 1.882.77No QC Reported 46Ca mg kg-1 ICP-OES2976789002 0.680.46No QC Reported 49Ca mg kg-1 ICP-OES263172000-0.33-0.45No QC Reported 52Ca mg kg-1 Flame AAS2732611192 -0.04-0.05No QC Reported 53Ca mg kg-1 ICP-OES240004202 -1.00-1.47No QC Reported 55Ca mg kg-1 ICP-MS303040.83No QC Reported 57Ca mg kg-1 ICP-OES290250.46DORM 4 58Ca mg kg-1 ICP-MS3086610482 1.001.43NIST 2976 59Ca mg kg-1 ICP-MS2596726002 -0.43-0.56IAEA 461 2 Cd mg kg-1 Graphite Furnace AAS 0.0190.0082 -3.29-2.98IAEA 461 6 Cd mg kg-1 ICP-MS0.0310.0132 -0.23-0.13No QC Reported 7 Cd mg kg-1 Graphite Furnace AAS 0.0290.0402 -0.81-0.16DORM 3 10Cd mg kg-1 ICP-MS0.0270.0042 -1.30-1.89TORT 3

42

TABLE 7. REPORTED RESULTS BY PARTICPANTS (cont.) Lab codeAnalyteUnit Instrumental MethodLab MeanLab U kz-score Zeta-score QC 11Cd mg kg-1 ICP-MS0.0290.0032 -0.91-1.53CUSTOM 12Cd mg kg-1 Flame AAS0.0360.0022 0.931.72IAEA 461 13Cd mg kg-1 ICP-MS0.0350.0032 0.600.98NIST 2976 14Cd mg kg-1 ICP-MS0.0320.0012 -0.04-0.08DORM 4 16Cd mg kg-1 ICP-MS0.0980.0802 16.311.64NIST 2976 17Cd mg kg-1 Graphite Furnace AAS 0.020-3.04No QC Reported 19Cd mg kg-1 Graphite Furnace AAS 0.0240.0082 -2.13-1.93NIST SRM 1566a 20Cd mg kg-1 Graphite Furnace AAS 0.0320.0091 -0.15-0.06NIST 1566b 21Cd mg kg-1 Graphite Furnace AAS 0.0390.0042 1.642.37IAEA 407 22Cd mg kg-1 Graphite Furnace AAS 0.0250.0052 -1.88-2.12DORM 4 23Cd mg kg-1 Hydride ICP-MS0.0310.0062 -0.31-0.35No QC Reported 25Cd mg kg-1 ICP-MS0.030-0.56NIST 2976 26Cd mg kg-1 POLAROGRAPHY0.9370.0482 224.4237.6IAEA 407 28Cd mg kg-1 ICP-MS0.3000.2002 66.412.68DOLT 4 29Cd mg kg-1 Graphite Furnace AAS 0.0270.0102 -1.22-0.92QTM114BT 31Cd mg kg-1 ICP-MS0.0320.0042 0.020.03IAEA 436 35Cd mg kg-1 ICP-MS0.0310.0032 -0.21-0.29No QC Reported 36Cd mg kg-1 ICP-MS0.028-1.18 TORT 42Cd mg kg-1 ICP-MS0.0490.0081.964.243.84IAEA 407 43Cd mg kg-1 ICP-OES0.0312 -0.31No QC Reported

43 TABLE 7. REPORTED RESULTS BY PARTICPANTS (cont.) Lab codeAnalyteUnit Instrumental MethodLab MeanLab U kz-score Zeta-score QC 44Cd mg kg-1 Graphite Furnace AAS 0.0450.0062 3.083.48IAEA 407 47Cd mg kg-1 Graphite Furnace AAS 0.0250.008-1.88-1.71DORM 4 48Cd mg kg-1 Graphite Furnace AAS 0.0200.0202 -3.04-1.23DORM 4 52Cd mg kg-1 Graphite Furnace AAS 0.2100.0402 44.098.85No QC Reported 53Cd mg kg-1 ICP-OES0.6000.1602 140.837.09No QC Reported 54Cd mg kg-1 Graphite Furnace AAS 0.0290.002-0.81-1.49IAEA 407 55Cd mg kg-1 ICP-MS0.22748.22No QC Reported 57Cd mg kg-1 ICP-MS0.029-0.77DORM 4 58Cd mg kg-1 ICP-MS0.0260.0012 -1.63-3.02NIST 2976 59Cd mg kg-1 ICP-MS0.0320.0062 0.020.02IAEA 461 60Cd mg kg-1 Graphite Furnace AAS 0.0410.0032 2.174.01IAEA 407 62Cd mg kg-1 ICP-MS0.0270.0052 -1.39-1.81NIST 2976 14CH3Hg mg kg-1 as HgGC-AFS0.5660.0432 0.530.69DORM 4 19CH3Hg mg kg-1 as HgCold Vapor AAS0.1510.1202 -5.73-5.02ERM 464 47CH3Hg mg kg-1 as HgCold Vapor AAS0.4570.137-1.11-0.89DORM 4 56CH3Hg mg kg-1 as HgCold Vapor AFS 561881.968450.52 12.5BCR 463 57CH3Hg mg kg-1 as HgHydride AFS 0.5850.82DORM 3 59CH3Hg mg kg-1as HgGC-AFS0.5830.1882 0.800.50IAEA 461 2 Co mg kg-1Flame AAS0.8630.2262 IAEA 461

44

TABLE 7. REPORTED RESULTS BY PARTICPANTS (cont.) Lab codeAnalyteUnit Instrumental MethodLab MeanLab U kz-score Zeta-score QC 5 Co mg kg-1 Neutron Activation0.0840.0042 SRM 1566b 6 Co mg kg-1 ICP-MS0.2590.0462 No QC Reported 10Co mg kg-1 ICP-MS0.1000.0282 No QC Reported 11Co mg kg-1 ICP-MS0.0770.0082 CUSTOM 13Co mg kg-1 ICP-MS0.1030.0062 NIST 2976 14Co mg kg-1 ICP-MS0.1380.0082 DORM 4 16Co mg kg-1 ICP-MS0.2620.0602 TORT 1 20Co mg kg-1 Neutron Activation0.2770.0201 NIST 1566b 21Co mg kg-1 Graphite Furnace AAS 0.0900.0492 IAEA 407 25Co mg kg-1 ICP-MS0.110NIST 2976 28Co mg kg-1 Neutron Activation0.1270.0402 NIST 1566b 31Co mg kg-1 ICP-MS0.1020.0102 IAEA 436 35Co mg kg-1 ICP-MS0.1140.0062 No QC Reported 36Co mg kg-1 ICP-MS0.080TORT 38Co mg kg-1 Neutron Activation0.0970.0202 IAEA 452 42Co mg kg-1 ICP-MS0.0940.0131.96IAEA 407 43Co mg kg-1 ICP-OES0.1000.0402 No QC Reported 47Co mg kg-1 Graphite Furnace AAS 0.2230.070TORT 2 49Co mg kg-1 ICP-MS11130TORT 3 53Co mg kg-1 ICP-OES8.232.942 No QC Reported

45 TABLE 7. REPORTED RESULTS BY PARTICPANTS (cont.) Lab codeAnalyteUnit Instrumental MethodLab MeanLab U kz-score Zeta-score QC 57Co mg kg-1 ICP-MS0.119DORM 4 58Co mg kg-1 ICP-MS0.1070.0052 NIST 2976 59Co mg kg-1 ICP-MS0.0930.0122 IAEA 461 2 Cr mg kg-1 Graphite Furnace AAS 3.730.752 IAEA 461 5 Cr mg kg-1 Neutron Activation3.660.242 NONE 6 Cr mg kg-1 ICP-MS2.750.682 No QC Reported 7 Cr mg kg-1 Graphite Furnace AAS 2.801.742 DORM 3 10Cr mg kg-1 ICP-MS4.111.082 TORT 3 11Cr mg kg-1 ICP-MS2.290.352 CUSTOM 12Cr mg kg-1 Flame AAS4.460.402 IAEA 461 13Cr mg kg-1 ICP-MS4.910.432 NIST 2976 14Cr mg kg-1 ICP-MS4.390.242 DORM 4 15Cr mg kg-1 XRF 2.281.192 NIST 2976 16Cr mg kg-1 ICP-MS2.920.072 TORT 1 19Cr mg kg-1 Graphite Furnace AAS 3.540.502 NIST SRM 1566a 20Cr mg kg-1 Neutron Activation3.930.271 No QC Reported 21Cr mg kg-1 ICP-OES3.220.092 IAEA 407 23Cr mg kg-1 ICP-MS2.860.432 No QC Reported 25Cr mg kg-1 ICP-MS3.97NIST 2976 28Cr mg kg-1 Neutron Activation3.830.122 No QC Reported

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