SIM.8.10P Trace Elements in Drinking Water

Transcription

1 National Research Council Canada Institute for National Measurement Standards Conseil national de recherches Canada Institut des étalons nationaux de mesure SIM.8.10P Trace Elements in Drinking Water Part I and Part II Technical Report Scott Willie Ralph Sturgeon March 2004

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3 Table of Contents Introduction... 4 Participation... 4 Sample Preparation... Results... s... 7 Uncertainties... 7 Workshops... 7 Chromium... 8 Iron Nickel... 1 Copper Zinc Arsenic Cadmium Barium... 3 Lead Conclusions Acknowledgements References Appendix A Data... 4

4 Introduction Safe drinking water is fundamental to everyday life. The goal of SIM.8.10P is to determine state of the practice in SIM countries for the determination of trace elements in water. This report summarizes the results of two intercomparison exercises, SIM 8.10P, Part I and Part II, organized in 2003 and These were co-ordinated by the Chemical Metrology Group of the Institute for National Measurement Standards (INMS) of the National Research Council Canada (NRCC). SIM 8.10P is a follow-up to SIM.8.P2, conducted between October 1999 and September 2000 and co-ordinated by the National Institute of Standards and Technology (NIST), USA. Participation in SIM.8.10P Table 1 presents the timetable for SIM 8.10P, Part I and Part II. A call for participation was sent out to each country within the SIM Region. oratories were asked to respond directly to NRCC with their intention to participate. In addition to NMIs within SIM or their official designees, several additional laboratories were included in the exercise. The samples were distributed by courier from NRCC. The deadline for the submission of results for each exercise is listed in Table I. oratories were permitted to use their analytical method of choice to determine the primary elements for this study: Cr, Fe, Ni, Cu, Zn, As, Cd, Ba, and Pb. A full uncertainty budget in accordance with the GUM [1] was also requested from the participants. Table 2 lists the participants in SIM.8.10P. Seventeen laboratories participated in both Part I and Part II, four and six laboratories participated in only Part I and Part II, respectively. Table 1. Schedule for SIM.8.10P. Timeline Part I Part II Call for participation 8-Mar-03 1-Apr-04 Sample distribution 8-May Apr-04 Deadline for reporting results 5-Sep Sep-04 Results presented at SIM 2-Nov-03 3-Nov-04 Follow up workshop 5-Feb-04-4 SIM.8.10P

5 Table 2. Participants in SIM.8.10P. Institute Country Contact oratories that participated in Part I and Part II Instituto de Tecnología Minera - SEGEMAR Argentina Ricardo Crubellati INTI-CEQUIPE Argentina Celia Puglisi oratorio de Calidad Ambiental (LCA) Bolivia Hugo Guerrero Fundação Centro Tecnológico de Minas Gerais - CETEC Brazil Olguita Geralda Ferreira Rocha INMETRO Brazil Thiago de Oliveira Araujo Instituto de Pesquisas Tecnológicas, IPT Brazil Vera Ponçano SENAI/ CETIND Brazil Sérgio Motta National Research Council of Canada (NRCC) Canada Ralph Sturgeon CENMA Chile Pablo Richter-Duk, Ruben Verdugo INN Chile Nury Gras-Rebolledo Fundación Chile Chile Gabriela Massiff LACOMET Costa Rica Carlos Paniagua University of the West Indies Jamaica Robin Rattray West Indies Alumina Company, WINDALCO Jamaica Desmond Lawson Envirolab Peru Luis Bueno Carbajal oratorio Tecnológico del Uruguay, LATU Uruguay Nury Prat ICLAM SENCAMER Venezuela Haygas Kalustián oratories that participated in Part I Institute of Chemical Technology Czech Republic Miloslav Suchanek Physikalisch-Technische Bundesanstalt, (PTB) Germany Detlef Schiel Multipurpose oratory St. Kitts Milton Whittaker Caribbean Environmental Health Institute St. Lucia Andrew Lewis oratories that participated in Part II Comisión Nacional de Energía Atómica Argentina Silvia Farías oratorio Quimico Lambda S.A. Costa Rica Rafael Amon Bureau of Standards, Jamaica Jamaica James Kerr CENAM México Yosihito Mitani Centro para la Investigación de Recursos Acuaticos de Nicaragua Nicaragua Jorge Pitty INDICASAT / SENACYT Panamá Félix Rodríguez Trace Elements in Drinking Water 5

6 Sample Preparation Samples were prepared in-house at NRCC. Two 25 liter LDPE carboys were cleaned with 10 % (v/v) high purity nitric acid for 72 hours. Each carboy was emptied, rinsed with high purity water and refilled with 18 liters of bottled natural spring water (rador Laurentienne Inc., Quebec, Canada). This water was packaged in 18 liter plastic containers and distributed for use with water dispensers. The samples were acidified by addition of 100 ml of NRC sub-boiled high purity nitric acid. Samples were fortified with Cr, Fe, Ni, Cu, Zn, As, Cd, Ba, and Pb by adding appropriate amounts of 1000 µg/ml stock solutions (ICP Grade, SCP Science, Montreal, Quebec) prepared from high purity materials and traceable to NIST. Samples A and B were distributed as in Part I and Samples C and D in Part II. The fortified concentrations for Sample A and Sample C were chosen to approach the maximum acceptable limits of the USEPA and Canadian government guidelines for drinking water [2,3]. The fortified concentrations for Sample B and Sample D were approximately 10- fold greater. The resulting solutions were thoroughly mixed and sampled into precleaned 250 ml HDPE bottles. A homogeneity test for all elements was performed on six randomly selected samples. In all cases, the coefficient of variation was less than 1.2% with the exception of As (3%). The latter measurement represented variation inherent to the analytical technique used (ETAAS) rather than reflecting between bottle differences. The material was deemed stable for at least one year at room temperature based on NRCC experience with similar samples. Results The majority of results for Part I and Part II were received by the respective deadlines. The submitted results were compiled in a database and a copy was returned by to the participants for verification that no transcription errors had occurred. A few minor changes were made. In Part I, oratories 2, 20 and 21 submitted two independent results based on alternative detection methodologies. In such cases, the independent results are listed separately and are delineated as the laboratory number accompanied by an alphabetical suffix. Graphical representation of the results are presented on pages 8 to 43. The mean is shown as a square, and vertical error bars represent the reported expanded uncertainty. The assigned value is displayed as a solid horizontal line. Divergent data that would distort the graph are indicated with an arrow head near the graph s upper border. A table below the graph for each samples lists: the recommended values, uncertainties and instrumental techniques reported by the participants. As well, the source of the assigned value and, for comparative purposes, a summary of submitted results, is also provided for each sample. In some cases, obvious outliers were subjectively rejected from the overall summary. Appendix A lists the submitted data: the mean, uncertainty and maximum of six values for each laboratory. For Samples C and D a U following the uncertainty indicates that the laboratory reported an uncertainty value, otherwise, the uncertainty in the data is represented as a standard deviation of the replicate results. SIM.8.10P

7 s Part I The assigned values for Part I of this exercise were determined from results submitted by laboratories having successful BIPM/CIPM experience. Thus, SIM.8.10P could provide international comparability for trace element analysis in drinking water by linking intercomparison results for SIM nations with BIPM/CIPM key comparison participants. However, this restriction limited only data submitted by NRCC and PTB for calculation of the SIM.8.P10 Part I assigned values. In some cases, NRCC and PTB were able to employ the method of isotope dilution sector field inductively coupled plasma mass spectrometry (ID-SF-ICP-MS). The use of isotope dilution as a calibration method is considered a primary method when properly employed. Unfortunately, for monoisotopic elements or elements suffering severe interferences, other techniques must be used. The assigned values for Cr, Cu and Ni were calculated based on NRCC results using alternative methods of detection, such as inductively coupled atomic emission (ICP-AES) and electrothermal atomization atomic absorption (ETAAS). For As and Fe, the assigned value was based on only one NRCC method. Part II The assigned values in the follow up exercise were based on gravimetric calculations where possible. The exception was Ba in both Sample C and D and Ni in Sample C where analysis of the unspiked spring water found levels of analyte naturally present that could not be considered negligible. In these cases the NRCC values was used for comparative purposes. Uncertainties The majority of laboratories reported results with an uncertainty value calculated according to the principles outlined in the GUM [1]. Only a few participants included in their report details of the uncertainty budget calculation. Some laboratories did not state whether the uncertainty reported was an expanded uncertainty i.e., multiplied by the coverage factor, k. Major sources contributing to overall uncertainty identified by several participants were calibration and dilution factors. Workshop Following each of these two exercises the results were discussed by the participants at workshops in Caracas (November 2003), Costa Rica (February 2004) and Margarita Is. Venezuela (November 2004). Participants were encouraged to attend and make a brief presentation outlining their measurement method and model for calculating measurement uncertainty. Trace Elements in Drinking Water 7

8 Chromium Part I Sample A Concentration, oratory ETAAS ETAAS ETAAS 4 <2 ICP-AES ETAAS 12 ICP-AES ETAAS ETAAS ETAAS ICP-AES ETAAS ETAAS ICP-AES ICP-MS ICP-AES ETAAS A value of 11.2 was assigned to Cr in Sample A based on the ETAAS results from NRCC. No. of results Overall mean 11.8 Median 11.7 Sample S.D % C.I gravimetric SIM.8.10P

9 Chromium Part II Sample C 20 1 Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES ETAAS ETAAS ICP-AES ETAAS ICP-AES ETAAS ETAAS 11 ETAAS 1 <30 FAAS ICP-AES ETAAS ICP-MS ICP-AES ETAAS ICP-AES A value of.9 was assigned to Cr in Sample C based on the gravimetric calculation. No. of results 19 Overall mean.1 Median.0 Sample S.D % C.I. 1.4 gravimetric.9 Trace Elements in Drinking Water 9

10 Chromium Part I Sample B Concentration, a21b oratory ETAAS ICP-AES ETAAS ICP-AES ETAAS 84 7 ICP-AES ETAAS ETAAS FAAS ICP-AES ETAAS ETAAS ICP-AES ICP-MS ICP-AES 21a ETAAS 21b ICP-AES A value of 83.7 was assigned to Cr in Sample B based on the ETAAS and ICP-AES results from NRCC. No. of results 17 Overall mean 83.2 Median 84.0 Sample S.D % C.I. 5.5 gravimetric SIM.8.10P

11 Part II Sample D Chromium Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES ETAAS ETAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES ETAAS FAAS ICP-AES ETAAS ICP-MS ICP-AES FAAS ICP-AES A value of 100 was assigned to Cr in Sample D based on the gravimetric calculation. No. of results 20 Overall mean 99.2 Median 99.8 Sample S.D % C.I. 7.3 gravimetric 100 Trace Elements in Drinking Water 11

12 Iron Part I Sample A Concentration, oratory ETAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES ETAAS FAAS FAAS ICP-AES FAAS ETAAS ICP-AES ICP-AES ICP-AES A value of 79.5 was assigned to Fe in Sample A based on the ICP-AES results from NRCC. No. of results Overall mean 84.2 Median 79.5 Sample S.D % C.I gravimetric SIM.8.10P

13 Iron Part II Sample C Concentration, oratory ICP-AES ICP-AES FAAS ICP-AES ICP-AES FAAS FAAS ICP-AES ETAAS ICP-AES FAAS ICP-AES 0 37 FAAS FAAS FAAS ICP-AES ICP-MS ETAAS ICP-AES A value of 90.8 was assigned to Fe in Sample C based on the gravimetric calculation. No. of results 19 Overall mean 91.7 Median 91.2 Sample S.D % C.I gravimetric 90.8 Trace Elements in Drinking Water 13

14 Iron Part I Sample B Concentration, oratory FAAS ICP-AES FAAS ICP-AES ETAAS ICP-AES FAAS FAAS FAAS ICP-AES FAAS FAAS ICP-AES ICP-AES ICP-AES A value of 372 was assigned to Fe in Sample B based on the ICP-AES results from NRCC. No. of results Overall mean 357 Median 371 Sample S.D % C.I. 29 gravimetric 387 SIM.8.10P

15 Iron Part II Sample D Concentration, oratory ICP-AES ICP-AES FAAS ICP-AES ICP-AES FAAS FAAS FAAS ICP-AES ETAAS ICP-AES FAAS ICP-AES FAAS FAAS FAAS ICP-AES ICP-MS FAAS ICP-AES A value of 309 was assigned to Fe in Sample D based on the gravimetric calculation. No. of results 20 Overall mean 297 Median 298 Sample S.D % C.I. 21 gravimetric 309 Trace Elements in Drinking Water

16 Nickel Part I Sample A Concentration, a 2b oratory ETAAS 2a ETAAS 2b ICP-AES ETAAS ICP-AES ETAAS 24 9 ICP-AES ICP-AES ICP-AES ETAAS ETAAS ICP-AES ICP-MS ICP-AES ID-SF-ICP-MS A value of 22.3 was assigned to Ni in Sample A based on the ID- SF-ICP-MS results from NRCC. No. of results Overall mean 21.3 Median 20.3 Sample S.D % C.I. 1. gravimetric SIM.8.10P

17 Nickel Part II Sample C Concentration, <20 oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES ETAAS FAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES FAAS 1 <20 FAAS ICP-AES ETAAS ICP-MS ICP-AES ICP-MS A value of 2.4 was assigned to Ni in Sample C based on the gravimetric calculation. No. of results 18 Overall mean 25.9 Median 25.7 Sample S.D % C.I. 5.0 gravimetric 2.4 Trace Elements in Drinking Water 17

18 Nickel Part I Sample B Concentration, a 2b a21b oratory ETAAS 2a ETAAS 2b ICP-AES ETAAS ICP-AES ETAAS 13 8 ICP-AES FAAS ICP-AES ICP-AES FAAS FAAS ICP-AES ICP-MS 20 3 ICP-AES 21a ID-SF-ICP-MS 21b ICP-AES A value of 12 was assigned to Ni in Sample B based on the ID-SF-ICP-MS and ICP-AES results from NRCC. No. of results 17 Overall mean 7 Median 9 Sample S.D % C.I. 5.3 gravimetric SIM.8.10P

19 Nickel Part II Sample D Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES ETAAS FAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES FAAS FAAS FAAS ICP-AES ETAAS ICP-MS ICP-AES ICP-MS A value of 178 was assigned to Ni in Sample D based on the the gravimetric calculation. No. of results 20 Overall mean 177 Median 17 Sample S.D % C.I gravimetric 178 Trace Elements in Drinking Water 19

20 Copper Part I Sample A Concentration, a 21b oratory ETAAS ICP-AES ETAAS ICP-AES ETAAS 20 5 ICP-AES ETAAS ETAAS FAAS ICP-AES AAS ICP-AES 13 2 FAAS ETAAS ETAAS ICP-AES ICP-MS ICP-AES 21a ID-ICP-MS 21b ICP-AES A value of 1.5 was assigned to Cu in Sample A based on the ID- SF-ICP-MS and ICP-AES results from NRCC. No. of results 20 Overall mean.8 Median. Sample S.D % C.I. 2.0 gravimetric SIM.8.10P

21 Copper Part II Sample C Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES FAAS FAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES 29 9 FAAS FAAS FAAS ICP-AES ETAAS ICP-MS ETAAS ICP-MS A value of 17.4 was assigned to Cu in Sample C based on the gravimetric calculation. No. of results 20 Overall mean 17.5 Median 17.0 Sample S.D % C.I. 2. gravimetric 17.4 Trace Elements in Drinking Water 21

22 Copper Part I Sample B Concentration, a 21b oratory FAAS ICP-AES ETAAS ICP-AES ETAAS 17 5 ICP-AES FAAS 10 7 FAAS FAAS ICP-AES AAS ICP-AES 1 5 FAAS FAAS FAAS ICP-AES ICP-MS ICP-AES 21a ID-ICP-MS 21b ICP-AES A value of 12 was assigned to Cu in Sample B based on the ID-SF-ICP-MS and ICP-AES results from NRCC. No. of results 20 Mean* 13 Median* 11 Sample S.D.* 10 95% C.I.* gravimetric 12 * Two results not included. 22 SIM.8.10P

23 Copper Part II Sample D Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES FAAS FAAS FAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES FAAS FAAS FAAS ICP-AES ETAAS ICP-MS FAAS ICP-MS A value of 185 was assigned to Cu in Sample D based on the gravimetric calculation. No. of results 21 Mean 185 Median 183 Sample S.D % C.I. gravimetric 185 Trace Elements in Drinking Water 23

24 Zinc Part I Sample A Concentration, oratory FAAS ICP-AES FAAS ICP-AES ETAAS 50 ICP-AES ID-SF-ICP-MS FAAS FAAS FAAS FAAS ICP-AES AAS FAAS FAAS ICP-AES ICP-MS ICP-AES ID-SF-ICP-MS A value of 52.9 was assigned to Zn in Sample A based on the ID- SF-ICP-MS results from NRCC and ID-SF-ICP-MS results from PTB. No. of results 19 Overall mean 52.3 Median 52.7 Sample S.D % C.I SIM.8.10P

25 Zinc Part II Sample C Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES FAAS FAAS FAAS ICP-AES FAAS ICP-AES FAAS ICP-AES 59 5 FAAS 4 2 FAAS FAAS HR-ICP-MS ICP-AES FAAS ICP-MS FAAS ICP-AES A value of 47.4 was assigned to Zn in Sample C based on the gravimetric calculation. No. of results 22 Overall mean 45.8 Median 4.2 Sample S.D % C.I. 5.3 gravimetric 47.4 Trace Elements in Drinking Water 25

26 Zinc Part I Sample B Concentration, oratory FAAS ICP-AES FAAS ICP-AES ETAAS ICP-AES ID-SF-ICP-MS FAAS FAAS FAAS FAAS ICP-AES AAS FAAS FAAS ICP-AES ICP-MS ICP-AES ID-SF-ICP-MS A value of 1029 was assigned to Zn in Sample B based on the ID- SF-ICP-MS results from NRCC and ID-SF-ICP-MS results from PTB. No. of results 17 Mean* 1050 Median* 1044 Sample S.D.* 52 95% C.I.* 30 * Two results not included. 2 SIM.8.10P

27 Zinc Part II Sample D 1200 Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES FAAS FAAS FAAS ICP-AES FAAS ICP-AES FAAS ICP-AES FAAS FAAS FAAS HR-ICP-MS ICP-AES FAAS ICP-MS FAAS ICP-AES A value of 975 was assigned to Zn in Sample D based on the gravimetric calculation. No. of results 22 Mean 932 Median 9 Sample S.D % C.I. 975 gravimetric 975 Trace Elements in Drinking Water 27

28 Arsenic Part I Sample A Concentration, oratory HGAAS ETAAS ETAAS ICP-AES ETAAS ETAAS HGAAS ETAAS ETAAS HGAAS ICP-AES HGAAS ETAAS A value of 23.7 was assigned to As in Sample A based on the ETAAS results from NRCC. No. of results 13 Mean* 24.9 Median* 24.1 Sample S.D.* % C.I.* 3.1 gravimetric 23.0 * One result not included. 28 SIM.8.10P

29 Arsenic Part II Sample C 40 Concentration, oratory ICP-AES ICP-AES VGAAS ICP-AES ICP-AES HGAAS ETAAS ETAAS ICP-AES ETAAS ICP-AES ETAAS ETAAS FAAS ETAAS ICP-MS ICP-AES ICP-AES A value of 28.1 was assigned to As in Sample C based on the gravimetric calculation. No. of results 18 Mean 28.5 Median 28.4 Sample S.D..4 95% C.I. 3.7 gravimetric 28.1 Trace Elements in Drinking Water 29

30 Arsenic Part I Sample B Concentration, oratory HGAAS ETAAS ETAAS ICP-AES ETAAS ETAAS HGAAS ETAAS ICP-AES ETAAS HGAAS ICP-AES HGAAS ETAAS A value of 175 was assigned to As in Sample B based on the ETAAS results from NRCC. No. of results Mean* 179 Median* 178 Sample S.D.* 95% C.I.* 11 gravimetric 173 * Two results not included. 30 SIM.8.10P

31 Arsenic Part II Sample D Concentration, oratory ICP-AES ICP-AES VGAAS ICP-AES ICP-AES HGAAS ETAAS 8 17 ETAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES FAAS ETAAS ICP-MS ICP-AES ICP-AES A value of 175 was assigned to As in Sample B based on the gravimetric calculation. No. of results 18 Mean 17 Median 173 Sample S.D % C.I. 13 gravimetric 175 Trace Elements in Drinking Water 31

32 Cadmiun Part I Sample A 10 Concentration, a20b 21 oratory ETAAS ETAAS ETAAS ICP-AES ETAAS 7 7 ICP-AES ID-SF-ICP-MS ETAAS ETAAS ETAAS ICP-AES AAS ICP-AES ETAAS ETAAS ICP-AES ICP-MS 20a ICP-AES 20b ASV ID-SF-ICP-MS A value of 5.41 was assigned to Cd in Sample A based on the ID-SF-ICP-MS results from NRCC and ID-SF-ICP-MS results from PTB. No. of results 20 Overall mean* 5.25 Median* 5.28 Sample S.D.* 1 95% C.I.* 0.5 gravimetric SIM.8.10P

33 Cadmiun Part II Sample C 12 Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES ETAAS ETAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES 13 5 FAAS ETAAS FAAS HR-ICP-MS ICP-AES ETAAS ICP-MS ICP-AES ETAAS ICP-MS A value of.7 was assigned to Cd in Sample C based on the gravimetric calculation. No. of results 22 Overall mean 7.1 Median.7 Sample S.D % C.I. 1.0 gravimetric.7 Trace Elements in Drinking Water 33

34 Cadmiun Part I Sample B Concentration, a20b21a21b oratory ETAAS ETAAS ETAAS ICP-AES ETAAS 53 7 ICP-AES ID-SF-ICP-MS 8 9 ETAAS FAAS FAAS FAAS ICP-AES AAS ICP-AES ETAAS ETAAS ICP-AES ICP-MS 20a ICP-AES 20b ASV 21a ID-SF-ICP-MS 21b ICP-AES A value of 55.3 was assigned to Cd in Sample B based on the ID-SF-ICP-MS and ICP-AES results from NRCC and ID-SF- ICP-MS results from PTB. No. of results 22 Overall mean 54.3 Median 53.0 Sample S.D % C.I. 4.2 gravimetric 54.0 * One result not included. 34 SIM.8.10P

35 Cadmiun Part II Sample D 125 Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES FAAS ETAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES 7 12 FAAS 2 12 ETAAS FAAS HR-ICP-MS ICP-AES ETAAS ICP-MS ICP-AES FAAS ICP-MS A value of 59.2 was assigned to Cd in Sample D based on the the gravimetric calculation. No. of results 22 Overall mean 58.3 Median 58.7 Sample S.D % C.I..4 gravimetric 59.2 Trace Elements in Drinking Water 35

36 Barium Part I Sample A Concentration, oratory ICP-AES ETAAS ICP-AES ETAAS 3 12 ICP-AES ID-SF-ICP-MS ICP-AES ICP-AES ICP-MS ICP-AES A value of was assigned to Ba in Sample A based on the ICP-AES results from NRCC and ID-SF-ICP-MS results from PTB. No. of results 9 Mean* 4 Median* 4 Sample S.D.* 11 95% C.I.* 10 * One result not included. 3 SIM.8.10P

37 Barium Part II Sample C Concentration, oratory ICP-AES ETAAS ICP-AES ETAAS ICP-AES ICP-AES ICP-AES FAAS ICP-AES ICP-MS ICP-AES A value of was assigned to Ba in Sample C based on the ICP-AES results from NRCC. No. of results 11 Mean 135 Median 135 Sample S.D % C.I. 18 Trace Elements in Drinking Water 37

38 Barium Part I Sample B Concentration, oratory ICP-AES ETAAS ICP-AES ETAAS 5 20 ICP-AES 7 12 ID-SF-ICP-MS FAAS FAAS ICP-AES ICP-MS ICP-AES A value of 35 was assigned to Ba in Sample B based on the ICP-AES results from NRCC and ID-SF-ICP-MS results from PTB. No. of results 11 Overall mean 20 Median 40 Sample S.D. 8 95% C.I. 12 * Four results not included. 38 SIM.8.10P

39 Barium Part II Sample D 2000 Concentration, oratory ICP-AES ETAAS ICP-AES ETAAS FAAS ICP-AES ICP-AES ICP-AES FAAS ICP-AES FAAS ICP-MS ICP-AES A value of 1291 was assigned to Ba in Sample D based on the ICP-AES results from NRCC. No. of results 13 Overall mean 1287 Median 1287 Sample S.D % C.I Trace Elements in Drinking Water 39

40 Lead Part I Sample A Concentration, a20b 21 oratory ETAAS ETAAS ETAAS 4 < ICP-AES ETAAS 5 10 ICP-AES ID-SF-ICP-MS ETAAS ETAAS ETAAS ICP-AES AAS FAAS ETAAS ETAAS ICP-AES ICP-MS 20a ICP-AES 20b ASV ID-ICP-MS A value of 10.8 was assigned to Pb in Sample A based on the ID-SF-ICP-MS results from NRCC and ID-SF-ICP-MS results from PTB. No. of results 19 Mean* 11.1 Median* 10.8 Sample S.D.* 1. 95% C.I.* 1.0 gravimetric 10.8 * Two results not included. 40 SIM.8.10P

41 Lead Part II Sample C Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES ETAAS ETAAS ICP-AES ETAAS ICP-AES ETAAS ETAAS ETAAS 1 <20 FAAS HR-ICP-MS ICP-AES ETAAS ICP-MS ICP-AES ETAAS ICP-MS A value of. was assigned to Pb in Sample C based on the gravimetric calculation. No. of results 20 Mean. Median.3 Sample S.D % C.I. 2. gravimetric. Trace Elements in Drinking Water 41

42 Lead Part I Sample B Concentration, a20b 21 oratory ETAAS ETAAS ETAAS ICP-AES ETAAS ICP-AES ID-SF-ICP-MS ETAAS ETAAS FAAS ICP-AES AAS ICP-AES FAAS ETAAS ETAAS ICP-AES ICP-MS 20a ICP-AES 20b ASV ID-ICP-MS A value of 80.9 was assigned to Cr in Sample A based on the ID- SF-ICP-MS results from NRCC and ID-SF-ICP-MS results from PTB. No. of results 21 Mean 85.5 Median 81.0 Sample S.D % C.I gravimetric SIM.8.10P

43 Lead Part II Sample D Concentration, oratory ICP-AES ICP-AES ETAAS ICP-AES ICP-AES ETAAS ETAAS ICP-AES ETAAS ICP-AES ETAAS ICP-AES 7 20 ETAAS FAAS HR-ICP-MS ICP-AES ETAAS ICP-MS ICP-AES ETAAS ICP-MS A value of 83.2 was assigned to Cr in Sample D based on the gravimetric calculation. No. of results 21 Mean 81. Median 82.4 Sample S.D % C.I. 5.2 gravimetric 83.2 Trace Elements in Drinking Water 43

44 Conclusions It is clear from Part I of this study that for a few laboratories accuracy is difficult to achieve for the analysis of trace elements in drinking water at these concentration levels. Results were generally closer to the assigned values for Part II. Only a few laboratories were able to use multiple analytical techniques; thus one might question the use of ICP-AES for some low level metal analysis or the application of ETAAS for the higher concentrations. The concept of fit for purpose should be given more consideration. In a few cases, unrealistic uncertainty budgets were submitted for Part I, but many laboratories made commendable attempts to submit data based on the concept of the GUM for Part II. References [1] Guide to the Expression of Uncertainty in Measurement, ISO, Geneva, [2] Summary of Guidelines for Canadian Drinking Water Quality (04/02), Health Canada, April [3] U.S. Environmental Protection Agency (EPA) National Primary Drinking Water Regulations. URL: Acknowledgements The authors would like to thank V. Boyko, C. Scriver and L. Yang of NRCC for supplying analytical results for the intercomparison. 44 SIM.8.10P

45 Appendix A This page blank Trace Elements in Drinking Water 45

46 value U CHROMIUM Sample A < value U Sample B a b SIM.8.10P

47 value U CHROMIUM Sample C U U U U U U U U U <30 <30 <30 < U U U U U value U Sample D U U U U U U U U U U U U U U Trace Elements in Drinking Water 47

48 value U IRON Sample A nd value U Sample B SIM.8.10P

49 value U IRON Sample C U U U U U U U U U U U U value U Sample D U U U U U U U U U U U U U Trace Elements in Drinking Water 49

50 value U NICKEL Sample A a b a b value U Sample B a b a b SIM.8.10P

51 value U NICKEL Sample C U U U U U U U U <20 <20 <20 < U U U U U value U Sample D U U U U U U U U U U U U U Trace Elements in Drinking Water 51

52 value U COPPER Sample A a b value U Sample B a b SIM.8.10P

53 value U COPPER Sample C U U U U U U U U U U U U value U Sample D U U U U U U U U U U U U U Trace Elements in Drinking Water 53

54 value U ZINC Sample A value U Sample B SIM.8.10P

55 value U ZINC Sample C U U U U U U U U U U U U U U U value U Sample D U U U U U U U U U U U U U U U Trace Elements in Drinking Water 55

56 value U ARSENIC Sample A value U Sample B SIM.8.10P

57 value U ARSENIC Sample C U U U U U U U U U U U U U value U Sample D U U U U U U U U U U U U Trace Elements in Drinking Water 57

58 value U CADMIUM Sample A a b value U Sample B a b a b SIM.8.10P

59 value U CADMIUM Sample C U U U U U U U U U U U U U U value U Sample D U U U U U U U U U U U U U U Trace Elements in Drinking Water 59