Interlaboratory Proficiency Test 04/2017

Transkriptio

1 REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 5 7 Interlaboratory Proficiency Test /7 Metals in natural waters Mirja Leivuori, Riitta Koivikko, Timo SaraAho, Teemu Näykki, Keijo Tervonen, Sari Lanteri, Ritva Väisänen and Markku Ilmakunnas Finnish Environment Institute

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3 REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 5 7 Interlaboratory Proficiency Test /7 Metals in natural waters Mirja Leivuori, Riitta Koivikko, Timo SaraAho, Teemu Näykki, Keijo Tervonen, Sari Lanteri, Ritva Väisänen and Markku Ilmakunnas SYKE Helsinki 7 Finnish Environment Institute

4 REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 5 7 Finnish Environment Institute SYKE Proftest SYKE Layout: Markku Ilmakunnas The publication is also available in the Internet: helda.helsinki.fi/syke ISBN (pbk.) ISBN (PDF) ISSN (print) ISSN (Online) Author(s): Mirja Leivuori, Riitta Koivikko, Timo SaraAho, Teemu Näykki, Keijo Tervonen, Sari Lanteri, Ritva Väisänen and Markku Ilmakunnas Publisher and financier of publication: Finnish Environment Institute (SYKE) P.O. Box, FI5 Helsinki, Finland, Phone , syke.fi. Year of issue: 7

5 ABSTRACT Interlaboratory Proficiency Test /7 Proftest SYKE carried out the proficiency test (PT) for analysis of elements in natural and domestic waters in AprilMay 7. The measurands were: Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V, and Zn. Three sample types were: synthetic, domestic and natural (river) water. In total participants joined in the PT. In this proficiency test 9 % of the results were satisfactory when deviation of 5 % from the assigned value was accepted. Basically, either the metrologically traceable concentration, the calculated concentration, the robust mean, or the mean of the results reported by the participants was used as the assigned value for the measurands. The evaluation of the performance of the participants was carried out using s. Warm thanks to all the participants of this proficiency test! Keywords: water analysis, metals, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V, Zn, water, environmental laboratories, proficiency test, interlaboratory comparisons TIIVISTELMÄ Laboratorioiden välinen pätevyyskoe /7 Proftest SYKE järjesti pätevyyskokeen ympäristönäytteitä analysoiville laboratorioille huhtitoukokuussa 7. Pätevyyskokeessa määritettiin synteettisestä näytteestä sekä talous ja luonnonvedestä seuraavat metallit: Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V ja Zn. Pätevyyskokeeseen osallistui yhteensä osallistujaa. Koko tulosaineistossa hyväksyttäviä tuloksia oli 9 %, kun vertailuarvosta sallittiin 5 %:n poikkeama. Osallistujien pätevyyden arviointi tehtiin zarvon avulla. Testisuureen vertailuarvona käytettiin metrologisesti jäljitettävää pitoisuutta, laskennallista pitoisuutta, osallistujien ilmoittamien tulosten robustia keskiarvoa tai keskiarvoa. Kiitos pätevyyskokeen osallistujille! Avainsanat: vesianalyysi, metallit, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V, Zn, vesi ja ympäristölaboratoriot, pätevyyskoe, laboratorioiden välinen vertailumittaus SAMMANDRAG Provningsjämförelse /7 Proftest SYKE genomförde en provningsjämförelse i aprilmaj 7, som omfattade bestämningen av Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V och Zn i natur och hushållsvatten. Tillsammans laboratorier deltog i jämförelsen. I jämförelsen var 9 % av alla resultaten tillfredsställande, när avvikelsen 5 % från referensvärdet accepterades. Som referensvärde av analytens koncentration användes mest det metrologiska spårbara värdet, teoretiska värdet, robust medelvärdet eller medelvärdet av deltagarnas resultat. Ett varmt tack till alla deltagarna i testet! Nyckelord: vattenanalyser, metaller, Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V, Zn, provningsjämförelse, vatten och miljölaboratorier

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7 CONTENTS Abstract Tiivistelmä Sammandrag... Introduction... 7 Organizing the proficiency test Responsibilities s Samples and delivery Homogeneity and stability studies Feedback from the proficiency test Processing the data Pretesting the data Assigned values Standard deviation for proficiency assessment and... Results and conclusions.... Results.... Analytical methods... Uncertainties of the results... 5 Evaluation of the results Summary Summary in Finnish... 7 References... 8 APPENDIX : s in the proficiency test... 9 APPENDIX : Preparation of the samples... APPENDIX : Homogeneity of the samples... APPENDIX : Feedback from the proficiency test... APPENDIX 5 : Evaluation of the assigned values and their uncertainties... APPENDIX 6 : Terms in the results tables... 5 APPENDIX 7 : Results of each participant... 6 APPENDIX 8 : Summary of the s... 8 APPENDIX 9 : s in ascending order... 5 APPENDIX : Results grouped according to the methods... 7 APPENDIX : Significant differences in the results reported using different methods APPENDIX : Estimation of the measurement uncertainties reported by the participants Proftest SYKE MET /7 5

8 6 Proftest SYKE MET /7

9 Introduction Proftest SYKE carried out the proficiency test (PT) for analysis of elements in natural and domestic waters in AprilMay 7 (MET /7). The measurands were: Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V and Zn. Three sample types were: synthetic, domestic and natural (river) water. In total participants joined in the PT. In the PT the results of Finnish participants providing environmental data for Finnish environmental authorities were evaluated. Additionally, other water and environmental laboratories were welcomed in the proficiency test. Finnish Environment Institute (SYKE) is appointed National Reference Laboratory in the environmental sector in Finland. The duties of the reference laboratory include providing interlaboratory proficiency tests and other comparisons for analytical laboratories and other producers of environmental information. This proficiency test has been carried out under the scope of the SYKE reference laboratory and it provides an external quality evaluation between laboratory results, and mutual comparability of analytical reliability. The proficiency test was carried out in accordance with the international guidelines ISO/IEC 7 [], ISO 58 [] and IUPAC Technical report []. The Proftest SYKE has been accredited by the Finnish Accreditation Service as a proficiency testing provider (PT, ISO/IEC 7, The organizing of this proficiency test is included in the accreditation scope of the Proftest SYKE. Organizing the proficiency test. Responsibilities Organizer: Proftest SYKE, Finnish Environment Institute (SYKE), Laboratory Centre Hakuninmaantie 6, FI Helsinki, Finland Phone: proftest@environment.fi The responsibilities in organizing the proficiency test were as follows: Mirja Leivuori coordinator Riitta Koivikko substitute for coordinator Keijo Tervonen technical assistance Markku Ilmakunnas technical assistance Sari Lanteri technical assistance Ritva Väisänen technical assistance Timo SaraAho analytical expert (metals, IDICPMS) Teemu Näykki analytical expert (Hg, IDICPMS) Proftest SYKE MET /7 7

10 . s In total participants joined in this proficiency test (Appendix ), 6 from Finland and from other EU countries. One participant reported two result sets. Altogether 95 % of the reported results were measured using accredited analytical methods at least for a part of the measurands. For this proficiency test, the organizing laboratory (T, ISO/IEC 75, has the code 6 (SYKE, Helsinki).. Samples and delivery Three types of samples were delivered to the participants: synthetic, domestic and natural (river) water. The sample preparation is described in details in the Appendix. When preparing the samples, the purity of the used sample vessels was controlled. The randomly chosen sample vessels were filled with deionized water and the purity of the sample vessels was controlled after three days by analyzing Cd, Cu, Hg, and Zn. According to the test results all used vessels fulfilled the purity requirements. The synthetic sample AM was prepared from the NIST traceable commercial reference material produced by Inorganic Ventures. The synthetic sample AHg was prepared by diluting from the NIST traceable AccuTrace TM Reference Standard produced by AccuStandard, Inc. The samples DM and DHg were domestic water collected from Helsinki with additions of single element standard solutions (Merck CertiPUR, Appendix ). The river water was collected from Porvoo, the southern Finland, for the sample NM and NHg. Some additions of single element standard solutions (Merck CertiPUR ) were used in preparation of the river water samples (Appendix ). The water samples were acidified with nitric acid with the exception of samples for mercury, which were acidified with the hydrochloric acid. The samples were delivered on April 7 to the international participants and on 5 April 7 to the national participants. The samples arrived to the participants on 6 April 7. The samples were requested to be measured as follows: Mercury (AHg, GHg and NHg) latest on 5 May 7 The other samples latest on May 7 The results were requested to be reported latest on 5 May 7. s delivered the results mainly accordingly, one participant reported the results on the next day. The preliminary results were delivered to the participants via ProftestWEB and on May 7.. Homogeneity and stability studies The homogeneity of the samples was tested by analyzing various tested measurands. More detailed information of homogeneity studies is shown in Appendix. According to the homogeneity test results, all samples were considered homogenous. The synthetic samples were prepared from traceable certified reference materials. However, homogeneity of these was checked by parallel measurements of two samples and they were considered homogenous. 8 Proftest SYKE MET /7

11 Based on the earlier similar proficiency tests the water samples are known to be stable over the given time period for the test..5 Feedback from the proficiency test The feedback from the proficiency test is shown in Appendix. The comments from the participants mainly dealt with comments to the technical execution e.g. information for the parallel results. The comments from the provider are mainly focused to recommendations for method validation. All the feedback is valuable and is exploited when improving the activities..6 Processing the data.6. Pretesting the data The normality of the data was tested by the KolmogorovSmirnov test. The outliers were rejected according to the Grubbs or Hampel test before calculating the mean. The results, which differed from the data more than SD rob 5 or 5 % from the robust mean, were rejected before the statistical results handling. The replicate results were tested using the Cochran test. If the result has been reported as below detection limit, it has not been included in the statistical calculations. If the participant did not report the result of replicate measurements when requested, their result was excluded when setting the assigned value. More information about the statistical handling of the data is available from the Guide for participant []..6. Assigned values For the synthetic sample AM the NIST traceable calculated concentrations were used as the assigned values, with the exception of B, Hg and Pb. The assigned values for Hg and Pb are based on the results of the metrologically traceable isotope dilution (ID) ICPMS technique. Also for the samples DM, DHg, NM, and NHg the results based on IDICPMS results were used for Hg and Pb. The IDICPMS method is accredited for soluble lead in synthetic and natural waters and for soluble mercury in synthetic, natural and waste waters in the scope of the calibration laboratory (K5, ISO/IEC 75, Basically, for the other samples and measurands the robust mean value was used as the assigned value. If the number of results was low, the mean value was reported as the assigned value (n(stat)<, AM: B; DM: As, B, Ba, Co, Ni, Sb, Se, Sr, S tot, Ti, U, V; NM: B, Sn, Sr, Ti, U). The robust mean or the mean are not metrologically traceable assigned values. When it was not possible to have metrologically traceable assigned values, the robust mean or the mean value of the results was the best available value to be used as the assigned value. The reliability of the assigned values was statistically tested according to the IUPAC Technical report []. For the calculated assigned values the expanded measurement uncertainty (U pt, k=) was estimated by using the standard uncertainties associated with individual operations involved in Proftest SYKE MET /7 9

12 the sample preparation. The main individual source of the uncertainty was the uncertainty of the concentration in the stock solution. For the metrologically traceable mercury and lead results, the uncertainty is the expanded measurement uncertainty of the IDICPMS method. When the robust mean or the mean was used as the assigned value, the uncertainty was calculated using the robust standard deviation or standard deviation, respectively [, ]. The uncertainty of the calculated assigned value and the metrologically traceable value for metals in the synthetic samples varied between.5 and 6 %. When using the robust mean or the mean of the participant results as the assigned value, the uncertainties of the assigned values were between.6 and % (Appendix 5). After reporting the preliminary results, the uncertainty of metrologically traceable value of Hg has been changed for the synthetic sample AHg and the domestic water sample DHg from % to 6 %. The participant can recalculate their zeta values with the formula given in the preliminary results or in the Guide for participant []. After reporting of the preliminary results no changes to the assigned values have been done..6. Standard deviation for proficiency assessment and The standard deviation for the proficiency assessment was estimated based on the uncertainty of the assigned value, the concentrations of the measurand, the results of homogeneity and stability tests, and the longterm variation in the former proficiency tests. The standard deviation for the proficiency assessment ( s pt at the 95 % confidence level) was set to 5 % depending on the sample and measurand. After reporting the preliminary results no changes have been done for the standard deviations of the proficiency assessment values. When using the robust mean as the assigned value, the reliability was tested according to the criterion u pt / s pt., where u pt is the standard uncertainty of the assigned value (the expanded uncertainty of the assigned value (U pt ) divided by ) and s pt is the standard deviation for proficiency assessment [, ]. When testing the reliability of the assigned value the criterion was mainly fulfilled and the assigned values were considered reliable. The reliability of the target value of the standard deviation and the corresponding was estimated by comparing the deviation for proficiency assessment (s pt ) with the robust standard deviation of the reported results (s rob ) [, ]. The criterion s rob / s pt <. was mainly fulfilled. In the following cases, the criterion for the reliability of the assigned value was not met and, therefore, the evaluation of the performance is weakened in this proficiency test: Sample NM Measurand As, Se Proftest SYKE MET /7

13 Results and conclusions. Results The terms used in the results tables are presented in Appendix 6. The results and the performance of each participant are presented in Appendix 7 and the summary of the results in Table. The summaries of s are shown in Appendix 8. In Appendix 9 the s are shown in the ascending order. The reported results with their expanded uncertainties (k=) grouped according to the methods are presented in Appendix. The robust standard deviations of the results varied from % to % (Table ). The robust standard deviation of results was lower than % for 9 % of the results. Standard deviations higher than % apply for Hg in the synthetic and domestic water samples (AHg, DHg) and for As and Se in the river water sample (NM, Table ). The robust standard deviations for water samples were somewhat higher than in the previous similar proficiency test MET 6/6, where the deviations varied from.5 % to 5.5 % [5]. Table. The summary of the results in the proficiency test MET /7. Measurand Sample Unit Assigned value Mean Rob. mean Median SD rob SD rob % x spt % n (all) Acc z % Al AM DM NM As AM DM NM B AM DM NM Ba AM DM NM Cd AM DM NM Co AM DM NM Cr AM DM NM Cu AM DM NM Fe AM DM NM Proftest SYKE MET /7

14 Table. The summary of the results in the proficiency test MET /7. Measurand Sample Unit Assigned value Mean Rob. mean Median SD rob SD rob % x spt % n (all) Acc z % Hg AHg DHg NHg Mn AM DM NM Mo AM DM NM Ni AM DM NM Pb AM DM NM Sb AM DM NM Se AM DM NM Sn AM DM NM Sr AM DM NM Stot AM mg/l DM mg/l NM mg/l Ti AM DM NM U AM DM NM V AM DM NM Zn AM DM NM Rob. mean: the robust mean, SD rob: the robust standard deviation, SD rob %: the robust standard deviation as percent, s pt %: the standard deviation for proficiency assessment at the 95 % confidence level, Acc z %: the results (%), where z, n(all): the total number of the participants. Proftest SYKE MET /7

15 . Analytical methods The participants were allowed to use different analytical methods for the measurands in the PT. The used analytical methods and results of the participants grouped by methods are shown in more detail in Appendix. The statistical comparison of the analytical methods was possible for the data where the number of the results was 5. The statistically significant differences between the results are shown in Appendix. Effect of measurement methods on elemental results The most commonly used analytical method was ICPMS, followed by ICPOES. Some participants used GAAS or FAAStechniques (Appendix ). In many cases the number of results was too low for the statistical comparison of the analytical methods (Appendix ). No statistical differences between analytical techniques were observed except between ICPMS and ICPOES results for Al and Zn in the synthetic sample AM and for Zn in the river water sample NM (Appendix ). In each case the ICPMS results were lower than the ICPOES results. Recoveries that are too high may be caused by spectral interferences (overlapping wavelengths in emission spectrometry, polyatomic or isobaric interferences in mass spectrometry), matrix effects or contamination. Matrix effects can often be overcome by matrix matching the calibration standards, however this is often difficult with environmental samples since the elemental concentrations vary a lot even within the same sample type. As a general note, a low recovery may be an indication of loss of measurand which can occur during sample pretreatment (e.g. volatilization during acid digestion) or measurement (e.g. GAAS analysis). It may also be caused by incorrect background correction (ICPOES) or matrix effects. According to the results of this PT, majority of the participants results remained lower than the assigned values of Pb, Sb and V for the sample AM. However the differences were generally within the reported measurement uncertainties of the participants. Effect of measurement methods on mercury results Mercury was measured mostly by using the techniques based on ICPMS or cold vapor CVAFS, followed by cold vapor CVAAS technique. One participant used CVICPMS for mercury (Appendix ). Between the reported measuring methods no statistically significant differences were found. For determination of assigned value of mercury (and also lead), high accuracy isotope dilution ICPMS method was applied. Generally, the differences in mercury results are mainly due to different pretreatment procedures. Analytical techniques have less effect on the results, but for example using CVAFS lower detection limits can be achieved compared to CVAAS. CVICPMS is known to have very competent detection limits as well. For water samples hydrochloric acid is recommended for sample preservation and BrCl is recommended for oxidation of mercury species. Proftest SYKE MET /7

16 Uncertainties of the results The expanded uncertainties (k=) of the reported results were reported by 95 % of the participants, at least for some of their results (Table, Appendix ). Several approaches were used for estimating the measurement uncertainty (Appendix ). The most used approach was based on the internal quality data with sample replicates and the method validation data [6]. MUkit measurement uncertainty software for the estimation of the uncertainties was used by at maximum six participants (Appendix ) [7]. The free software is available in the webpage: Generally, the used approach for estimating measurement uncertainty did not make definite impact on the uncertainty estimates. The range of the reported uncertainties varied between the measurands and the sample types. As can be seen in Table, some of the participants have overestimated their expanded (k=) measurement uncertainty. Very high measurement uncertainties (i.e. 5 % or higher) should not exist, unless the measured concentration is near to the limit of quantification. However, the number of under or overestimations has decreased during past few years. In this PT the participants did not report expanded uncertainties below 5%, which could commonly be considered unrealistic uncertainty value for routine laboratories. Table. The range of the expanded measurement uncertainties (U pt %, k=) reported by the participants. Measurand AM/AHg, Upt % DM/DHg, Upt % NM/NHg, Upt % Al As B Ba 5 Cd Co Cr 5 Cu 9 9 Fe Hg Mn Mo Ni Pb 8 Sb Se Sn Sr Stot 7 7 Ti 5 U V Zn Proftest SYKE MET /7

17 In order to promote the enhancement of environmental measurements quality standards and traceability, the national quality recommendations for data entered into the water quality registers have been published in Finland [8]. The recommendation for measurement uncertainties for all tested measurands in natural waters is 5 %. In this proficiency test some of the participants had their measurement uncertainties within this limit, while some did not achieve it. However, harmonization of the uncertainties estimation should be continued. 5 Evaluation of the results The evaluation of the participants was based on the s, using the assigned values and the standard deviation for performance assessments (Appendix 6). The s were interpreted as follows: Criteria z Performance Satisfactory < z < Questionable z Unsatisfactory In total, 9 % of the results were satisfactory when deviation of 5 % from the assigned value was accepted. Altogether 95 % of the participants used accredited analytical methods at least for a part of the measurands and 9 % of their results were satisfactory. In the previous similar proficiency test MET 6/6 the performance was satisfactory for 9 % of the results when deviation 5 5 % from the assigned value was accepted, and the sediment sample was included in the PT [5].The summary of the performance evaluation and comparison to the previous performance is presented in Table. Table. Summary of the performance evaluation in the proficiency test MET /7. Sample Satisfactory results (%) Accepted deviation from the assigned value (%) Remarks AM, 9 5 Difficulties in measurements for Hg (AHg), Al and AHg Sb (AM), < 8% satisfactory results. In the previous PTs MET 6/6 and MET /5 the performance was satisfactory for 89 % and 88 % DM, DHg NM, NHg of the results, respectively [5, 8]. 9 5 Mainly good performance. Difficulties in measurements for B and Stot (DM), < 8% satisfactory results. In the previous PT MET 6/6 the performance was satisfactory for 89 % of the results, when accepting deviation 5 5 % from the assigned value [5]. 9 5 Mainly good performance. Only approximate assessment for As and Se Difficulties in measurements for As, < 8% satisfactory results. In the previous PTs MET 6/6 and MET /5 the performance was satisfactory for 9 % and 9 % of the results, respectively [5, 8]. Proftest SYKE MET /7 5

18 The satisfactory results varied between 89 % and 9 % for the tested sample types (Table ). For the synthetic sample AM all results for Co, Fe, Mn, Sr and U were satisfactory. For B and Sb measurements from the sample AM the performance was better (9 % and 77 % satisfactory results, respectively) than in the previous PT MET 8/ (7 % and 7 % satisfactory results, respectively) []. The share of satisfactory results in the synthetic sample AM was the lowest for Hg, about 69 %. The tested Hg concentration was low and the share of satisfactory results was lower than in the previous proficiency test PT MET 6/6, where the share was 9 % for the concentration.5 and the allowed deviation was % from the assigned value [5]. For the domestic water sample DM all results for Co, Cr, Cu, Mn, Se, Sn, Sr, U, and Zn were satisfactory. For the natural (river) water sample NM all results for Ba, Mn, Sn, Sr, Ti, U, V, and Zn were satisfactory. For B and Sb measurements of the sample NM the performance was mainly at the same level (8 % and 87 % satisfactory results, respectively) than in the previous similar PT MET 8/ (85 % and 9 % satisfactory results, respectively) []. 6 Summary Proftest SYKE carried out the proficiency test (PT) for analysis of elements in natural and domestic waters in AprilMay 7. The measurands were: Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V, and Zn. Three sample types were: synthetic, domestic and natural (river) water. In total participants joined in the PT. For the synthetic sample AM the NIST traceable calculated concentrations were used as the assigned values with the exception of B, Hg and Pb. The assigned values for Hg and Pb were based on the results of the metrologically traceable isotope dilution (ID) ICPMS technique. Also for the samples DM, DHg, NM, and NHg the results based on IDICPMS results were used for Hg and Pb. Basically, for other samples and measurements the robust mean or the mean value was used as the assigned value. If the number of results was low, basically the mean value was reported as the assigned value (n(stat)<, AM: B; DM: As, B, Ba, Co, Ni, Sb, Se, Sr, S tot, Ti, U, V; NM: B, Sn, Sr, Ti, U). The uncertainty for the assigned value was estimated at the 95 % confidence interval and it was between.5 and 6 % for the calculated and metrologically traceable assigned values and for assigned values based on the robust mean or the mean it was between.6 %. The evaluation of the performance was based on the s, which were calculated using the standard deviation for proficiency assessment at 95 % confidence level. In this proficiency test 9 % of the data was regarded satisfactory when the result were accepted to deviate from the assigned values to 5 %. Altogether 95 % of the participants used accredited methods at least for a part of measurements and 9 % of their results were satisfactory. 6 Proftest SYKE MET /7

19 7 Summary in Finnish Proftest SYKE järjesti ympäristönäytteitä analysoiville laboratorioille pätevyyskokeen huhtitoukokuussa 7. Pätevyyskokeessa määritettiin Al, As, B, Ba, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, Ti, U, V ja Zn synteettisestä näytteestä sekä talous ja luonnonvedestä. Pätevyyskokeessa oli yhteensä osallistujaa. Testisuureen vertailuarvona käytettiin laskennallista pitoisuutta, osallistujien tulosten robustia keskiarvoa tai keskiarvoa. Lyijylle ja elohopealle käytettiin metrologisesti jäljitettävää tavoitearvoa osalla testinäytteistä. Vertailuarvolle laskettiin mittausepävarmuus 95 % luottamusvälillä. Vertailuarvon laajennettu epävarmuus oli,5 ja 6 % välillä laskennallista tai metrologisesti jäljitettävää pitoisuutta vertailuarvona käytettäessä ja muilla välillä,6 %. Pätevyyden arviointi tehtiin zarvon avulla ja tulosten sallittiin poiketa vertailuarvosta 5 %. Koko aineistossa hyväksyttäviä tuloksia oli 9 %. Osallistujista 95 % käytti akkreditoituja määritysmenetelmiä ainakin osalle määrityksistään ja näistä tuloksista oli hyväksyttäviä 9 %. Proftest SYKE MET /7 7

20 REFERENCES. SFSEN ISO 7,. Conformity assessment General requirements for Proficiency Testing.. ISO 58, 5. Statistical methods for use in proficiency testing by interlaboratory comparisons.. Thompson, M., Ellison, S. L. R., Wood, R., 6. The International Harmonized Protocol for the Proficiency Testing of Analytical Chemistry laboratories (IUPAC Technical report). Pure Appl. Chem. 78: 596, Proftest SYKE Guide for laboratories: Running proficiency test 5. Leivuori, M., Koivikko, R., SaraAho, T., Näykki, T., Tervonen, K., Lanteri, S., Väisänen, R. and Ilmakunnas, M. 6. Interlaboratory Proficiency Test 6/6. Metals in natural water and sediment. Reports of Finnish Environment Institute /6. Helsinki. ( 6. Magnusson, B. Näykki. T., Hovind, H. and Krysell, M.,. Handbook for Calculation of Measurement Uncertainty in Environmental Laboratories. NT Technical Report 57. Nordtest. 7. Näykki, T., Virtanen, A. and Leito, I.,. Software support for the Nordtest method of measurement uncertainty evaluation. Accred. Qual. Assur. 7: 66. Mukit website: 8. Näykki, T. ja Väisänen, T. (toim.) 6. Laatusuositukset ympäristöhallinnon vedenlaaturekistereihin vietävälle tiedolle. Vesistä tehtävien analyyttien määritysrajat, mittausepävarmuudet sekä säilytysajat ja tavat.. uudistettu painos. Suomen ympäristökeskuksen raportteja /6. 57 s. ( 9. Leivuori, M., Koivikko, R., SaraAho, T., Näykki, T., Tervonen, K., Lanteri, S., Väisänen, R. and Ilmakunnas, M. 5. Interlaboratory Proficiency Test /5. Metals in natural water and soil. Reports of Finnish Environment Institute /5. Helsinki. ( Leivuori, M., Koivikko, R., SaraAho, T., Näykki, T., Björklöf, K., Tervonen, K., Lanteri, S., Väisänen, R. and Ilmakunnas, M. 5. Interlaboratory Proficiency Test 8/. Metals and mercury in waters. Reports of the Finnish Environment Institute 7/5. Helsinki. ( Ellison, S., L., R. and Williams, A. (Eds). () Eurachem/CITAC guide: Quantifying Uncertainty in Analytical Measurement, Third edition, ISBN ISO/IEC Guide 98:8. Uncertainty of measurement Part : Guide to the expression of uncertainty in measurement (GUM: 995). 8 Proftest SYKE MET /7

21 APPENDIX (/) APPENDIX : s in the proficiency test Country Finland Norway Sweden Institute Ahma ympäristö Oy, Oulu Ahma ympäristö, Seinäjoki Eurofins Environment Testing Finland Oy, Lahti Eurofins Viljavuuspalvelu, Mikkeli Freeport Cobalt Oy Kokemäenjoen vesistön vesiensuojeluyhdistys ry, Tampere Kymen Ympäristölaboratorio Oy LounaisSuomen vesi ja ympäristötutkimus Oy, Turku Luonnonvarakeskus, Viikki Blaboratorio Metropolilab Oy Nablabs Oy / Jyväskylä Novalab Oy SavoKarjalan Ympäristötutkimus Oy, Kuopio SeiLab Oy SGS Inspection Services Oy, Kotka SYKE Ympäristökemia Helsinki Eurofins Environment Norway A/S, Moss ACES, Stockholm University ALS Scandinavia AB, Luleå IVL, Svenska Miljöinstitutet AB, Göteborg Proftest SYKE MET /7 9

22 APPENDIX (/) APPENDIX : Preparation of the samples The synthetic sample AM was prepared by diluting from the NIST traceable certified reference materials produced by Inorganic Ventures. The synthetic sample AHg was prepared by diluting from the NIST traceable AccuTrace TM Reference Standard produced by AccuStandard, Inc. The water samples DM and NM were prepared by adding some separate metal solutions (Merck CertiPUR ) into the original water sample, if the original concentration was not high enough. Samples DHg and NHg were prepared by adding from the NIST traceable AccuTrace TM Reference Standard produced by AccuStandard, Inc., if the original concentration was not high enough. Al As B Ba Cd Co Cr Cu Fe Mn Mo Measurand Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value AM DM NM Pb Sb Se Sn Sr Stot Ti U V Zn Measurand Measurand Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value Original Dilution Addition Ass. value AM Original <.. Dilution Ni Hg Addition Ass. value Original = the original concentration, Addition = the addition concentration, Dilution = the ratio of dilution, Ass.value = the assigned value AHg DM DHg NM NHg Proftest SYKE MET /7

23 APPENDIX (/) APPENDIX : Homogeneity of the samples The homogeneity was checked for the selected samples and measurands as duplicate measurements. Criteria for homogeneity: s anal /s h <.5 and s sam <c, where s h = standard deviation for testing the homogeneity s anal = analytical deviation, standard deviation of the results in a sub sample s sam = between sample deviation, standard deviation of the results between sub samples c = F s all + F s anal, where s all = (. s h ), F and F are constants of F distribution derived from the standard statistical tables for the tested number of samples [, ]. Measurand/Sample Concentration [] n spt % sh% sh sanal sanal/sh sanal/sh<.5? ssam c ssam <c? Cd/DM Yes. Yes Cr/DM Yes.9 Yes Mo/DM Yes.8 Yes Sb/DM Yes. Yes Se/DM Yes.. Yes Sn/DM Yes.. Yes Ti/DM Yes. Yes U/DM Yes. Yes Zn/DM Yes.9. Yes Cd/NM Yes.7.7 Yes Cr/NM Yes.. Yes Mo/NM Yes.5 Yes Sb/NM Yes.. Yes Sn/NM Yes. Yes Ti/NM Yes.5 Yes U/NM Yes. Yes Zn/NM Yes.6.67 Yes Hg/DHg* Yes.. Yes Hg/NHg* Yes. Yes Pb/DM* Yes. Yes Pb/NM* Yes.7.7 Yes *) result based on the IDICPMS measurement s pt % = standard deviation for proficiency assessment Conclusion: The criteria were fulfilled for the tested measurands and the samples could be regarded as homogenous. Proftest SYKE MET /7

24 APPENDIX (/) APPENDIX : Feedback from the proficiency test FEEDBACK FROM THE PARTICIPANTS Comments on technical execution Action / Proftest 5 Bottle of sample DHg had leaked. The participant did not request new sample. The provider will pay more attention to careful closing of the bottles. 9 The sample arrival form did not open up from our electronic client interface. The provider tested that the form worked normally. The provider recommends using the The participant had not received the information letter of the PT. The instruction for reporting parallel results was contradictory. In the preliminary results reporting, was noticed a typing error in the Appendix. client interface via Internet Explorer. Provider had sent the information letter to all customers in the customer register and it should have been reached by the customer. In the future the provider will be more carefully with the instructions. The provider corrected the error and the preliminary results were redelivered to the domestic participants. Comments to the results Action / Proftest The participant informed that they reported barium results erroneously for arsenic in the sample DM. The corrected results were: Sample DM As:.5 and. The result was outlier in the statistical treatment, and thus did not affect the performance evaluation. If the result had been reported correctly, the result would have been satisfactory. The participant can recalculate the according to the Guide for participants []. FEEDBACK TO THE PARTICIPANTS Comments The participant reported below detection limit values (< ) for Mn in the sample DM, though the tested concentration was high enough to be measured (assigned value. ). The provider recommends the participant to validate their detection limit value.,7,8,,, For these participants the deviation of replicate measurements for some measurands and samples 5,6,8,9, were high and their results were Cochran outliers. The provider recommends the participants to, validate their deviation of replicate measurements. All After reporting the preliminary results, the uncertainty of metrologically traceable value of Hg has been changed for the synthetic sample AHg and the domestic water sample DHg from % to 6 %. The participant can recalculate their zeta values with the formula given in the preliminary results or in the Guide for participant []. Proftest SYKE MET /7

25 APPENDIX 5 (/) APPENDIX 5: Evaluation of the assigned values and their uncertainties Measurand Sample Unit Assigned value Upt Upt, % Evaluation method of assigned value upt/spt Al AM.6 Calculated value.6 DM Robust mean. NM Robust mean.6 As AM Calculated value.5 DM.5..8 Mean. NM.96.. Robust mean. B AM Mean.9 DM...8 Mean.8 NM Mean. Ba AM Calculated value.6 DM.7.9. Mean. NM Robust mean. Cd AM Calculated value.5 DM.. 5. Robust mean. NM.6..6 Robust mean. Co AM Calculated value.6 DM Mean. NM Robust mean. Cr AM.5..6 Calculated value.6 DM 5... Robust mean. NM Robust mean.8 Cu AM...5 Calculated value.5 DM 9 7. Robust mean. NM.8.5. Robust mean. Fe AM 56.6 Calculated value.6 DM 7 5. Robust mean. NM Robust mean.8 Hg AHg IDICPMS. DHg IDICPMS. NHg.7.5. IDICPMS.5 Mn AM Calculated value.5 DM... Robust mean. NM 8. Robust mean. Mo AM...7 Calculated value.7 DM... Robust mean.7 NM..7. Robust mean. Ni AM Calculated value.5 DM.9.. Mean. NM Robust mean.9 Pb AM.6.. IDICPMS. DM... IDICPMS. NM IDICPMS. Sb AM Calculated value.8 DM Mean. NM Robust mean. Proftest SYKE MET /7

26 APPENDIX 5 (/) Measurand Sample Unit Assigned value Upt Upt, % Evaluation method of assigned value upt/spt Se AM Calculated value. DM Mean.5 NM Robust mean. Sn AM Calculated value.5 DM Mean.5 NM Mean. Sr AM...7 Calculated value.7 DM..6.9 Mean.6 NM 7... Mean. Stot AM mg/l...5 Calculated value.5 DM mg/l Mean.9 NM mg/l 7... Robust mean. Ti AM Calculated value.7 DM Mean.5 NM Mean. U AM...7 Calculated value.5 DM Mean.5 NM...6 Mean. V AM Calculated value.7 DM Mean.5 NM Robust mean. Zn AM...7 Calculated value.7 DM... Robust mean. NM..9.7 Robust mean.5 U pt = Expanded uncertainty of the assigned value Criterion for reliability of the assigned value u pt/s pt <., where s pt= target value of the standard deviation for proficiency assessment u pt= standard uncertainty of the assigned value If u pt/s pt <., the assigned value is reliable and the s are qualified. Proftest SYKE MET /7

27 APPENDIX 6 (/) APPENDIX 6: Terms in the results tables Results of each participant Measurand The tested parameter Sample The code of the sample Calculated as follows: z = (x i x pt )/s pt, where x i = the result of the individual participant x pt = the assigned value s pt = the standard deviation for proficiency assessment Assigned value The value attributed to a particular property of a proficiency test item s pt % The standard deviation for proficiency assessment (s pt ) at the 95 % confidence level s s result The result reported by the participant (the mean value of the replicates) Md Median SD Standard deviation SD% Standard deviation, % n (stat) Number of results in statistical processing Summary on the s S satisfactory ( z ) Q questionable ( < z < ), positive error, the result deviates more than s pt from the assigned value q questionable ( < z < ), negative error, the result deviates more than s pt from the assigned value U unsatisfactory (z ), positive error, the result deviates more than s pt from the assigned value u unsatisfactory (z ), negative error, the result deviates more than s pt from the assigned value Robust analysis The items of data are sorted into increasing order, x, x, x i,,x p. Initial values for x * and s * are calculated as: x * = median of x i (i =,,...,p) s * =.8 median of x i x * (i =,,...,p) The mean x * and s * are updated as follows: Calculate =.5 s *. A new value is then calculated for each result x i (i =, p): { x *, if x i < x * x * i = { x * +, if x i > x * +, { x i otherwise The new values of x * and s * are calculated from: * * x xi / p s. ( x i x ) /( p ) The robust estimates x * and s * can be derived by an iterative calculation, i.e. by updating the values of x * and s * several times, until the process convergences []. Proftest SYKE MET /7 5

28 APPENDIX 7 (/) APPENDIX 7: Results of each participant Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Fe AM DM NM Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Al AM DM NM As AM NM Cd AM DM NM Cr AM DM NM Cu AM DM NM Fe AM DM NM Hg AHg DHg NHg Mn AM DM NM Ni AM DM NM Pb AM DM NM Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Al AM DM NM As AM DM NM Proftest SYKE MET /7

29 APPENDIX 7 (/) Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) B AM DM NM Ba AM DM NM Cd AM DM NM Co AM DM NM Cr AM DM NM Cu AM DM NM Fe AM DM NM Hg AHg DHg NHg Mn AM DM NM Mo AM DM NM Ni AM DM NM Pb AM DM NM Sb AM DM NM Se AM DM NM U AM DM NM V AM DM NM Proftest SYKE MET /7 7

30 APPENDIX 7 (/) Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Zn AM DM NM Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Al AM DM NM As AM DM NM B AM DM NM Ba AM DM NM Cd AM DM NM Co AM DM NM Cr AM DM NM Cu AM DM NM Fe AM DM NM Hg AHg.65 5 <, DHg.7 5 <, NHg Mn AM DM NM Mo AM DM NM Ni AM DM NM Pb AM DM NM Proftest SYKE MET /7

31 APPENDIX 7 (/) Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Sb AM DM NM Se AM DM NM Sn AM DM NM Sr AM DM NM Stot mg/l AM mg/l DM mg/l NM Ti AM 5. < DM 6.57 < NM U AM DM NM V AM DM NM Zn AM DM NM Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Al AM DM NM As AM DM NM B AM DM NM Ba AM DM NM Cd AM DM NM Co AM DM NM Proftest SYKE MET /7 9

32 APPENDIX 7 (5/) 5 Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Cr AM DM NM Cu AM DM NM Fe AM DM NM Hg AHg DHg NHg Mn AM DM NM Mo AM DM NM Ni AM DM NM Pb AM DM NM Sb AM DM NM Se AM DM NM Sn AM DM NM Sr AM DM NM Stot mg/l AM mg/l DM mg/l NM Ti AM DM NM U AM DM NM V AM DM NM Proftest SYKE MET /7

33 APPENDIX 7 (6/) 5 Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Zn AM DM NM Measurand Unit Sample Assigned value spt % 's result Md Mean SD SD% n (stat) Al AM DM NM As AM DM NM B AM DM NM Ba AM DM NM Cd AM DM NM Co AM DM NM Cr AM DM NM Cu AM DM NM Fe AM DM NM Hg AHg DHg NHg Mn AM DM NM Mo AM DM NM Ni AM DM NM Pb AM DM NM Proftest SYKE MET /7