Interlaboratory Proficiency Test 10/2018

Transkriptio

1 REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 9 Interlaboratory Proficiency Test /8 Metals in waste water and compost Mirja Leivuori, Riitta Koivikko, Timo SaraAho, Teemu Näykki, Aija Pelkonen, Keijo Tervonen, Sari Lanteri, Ritva Väisänen and Markku Ilmakunnas Finnish Environment Institute

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3 REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 9 Interlaboratory Proficiency Test /8 Metals in waste water and compost Mirja Leivuori, Riitta Koivikko, Timo SaraAho, Teemu Näykki, Aija Pelkonen, Keijo Tervonen, Sari Lanteri, Ritva Väisänen and Markku Ilmakunnas Finnish Environment Institute (SYKE), Laboratory Centre Finnish Food Safety Authority SYKE Helsinki 9 Finnish Environment Institute

4 REPORTS OF THE FINNISH ENVIRONMENT INSTITUTE 9 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, Aija Pelkonen, Keijo Tervonen, Sari Lanteri, Ritva Väisänen and Markku Ilmakunnas Publisher and financier of publication: Finnish Environment Institute (SYKE) Latokartanonkaari, FI79 Helsinki, Finland, Phone , syke.fi. Year of issue: 9

5 ABSTRACT TIIVISTELMÄ SAMMANDRAG Interlaboratory Proficiency Test /8 Proftest SYKE carried out the proficiency test (PT) for analysis of elements in waters and compost material in OctoberNovember 8. The measurands for the synthetic and waste water samples were: Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, V, and Zn. For the compost sample the measurands were: As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, S tot, V, and Zn. In total laboratories participated in the PT. In total, 9 % of the results evaluated with s were satisfactory when total deviation of 5 % from the assigned value was accepted. From the results evaluated with E n scores, 7 % were satisfactory. Basically, either the metrologically traceable concentration, calculated concentration, the robust mean, the mean or the median of the results reported by the participants was used as the assigned value for measurands. Warm thanks to all the participants of this proficiency test! Keywords: water analysis, compost, metals, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, Sb, Se, Sn, Sr, S tot, V, Zn, water and environmental laboratories, proficiency test, interlaboratory comparison TIIVISTELMÄ Laboratorioiden välinen pätevyyskoe /8 Proftest SYKE järjesti lokamarraskuussa 8 pätevyyskokeen laboratorioille, jotka määrittävät metalleja ja elohopeaa viemärilaitos ja teollisuusjätevesistä sekä lannoitteena käytettävästä kompostimateriaalista (MET /8). Pätevyyskokeessa määritettiin synteettisestä sekä jätevesinäytteistä testisuureet Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, V ja Zn. Kompostinäytteestä määritettiin testisuureet As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, S tot, V ja Zn. Pätevyyskokeeseen osallistui yhteensä laboratoriota. Koko aineistossa hyväksyttäviä zarvolla arvioituja tuloksia oli 9 %, kun tulosten sallittiin poiketa vertailuarvosta 5 %. Tuloksista, jotka arvioitiin E n arvolla, hyväksyttyjä oli 7 %. Testisuureen vertailuarvona käytettiin metrologisesti jäljitettävää pitoisuutta, laskennallista pitoisuutta, osallistujien ilmoittamien tulosten robustia keskiarvoa, keskiarvoa tai mediaania. Kiitos pätevyyskokeen osallistujille! Avainsanat: vesianalyysi, komposti, metallit, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, Sb, Se, Sn, Sr, S tot, V, Zn, vesi ja ympäristölaboratoriot, pätevyyskoe, laboratorioiden välinen vertailumittaus SAMMANDRAG Provningsjämförelse /8 Proftest SYKE genomförde en provningsjämförelse i oktobernovember 8, som omfattade bestämningen av Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, V och Zn i syntetiska provet och avloppsvatten. Från kompost provet bestämdes As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, S tot, V och Zn. Tillsammans laboratorier deltog i jämförelsen. I jämförelsen 9 % av resultaten som värderas med hjälp z värdet var acceptabla, när total deviation på 5 % från referensvärdet tillåten. Resultaten som värderades med hjälp E n värdet var 7 % acceptabla. Som referensvärde av analytens koncentration användes mest det metrologiska spårbara värdet, teoretiska värdet eller robust medelvärdet, medelvärdet eller median av deltagarnas resultat. Ett varmt tack till alla deltagarna i testet! Nyckelord: vattenanalyser, kompost, metaller, Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, Sb, Se, Sn, Sr, S tot, 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 evaluation... Results and conclusions.... Results.... Analytical methods Uncertainties of the results... 7 Evaluation of the results Summary... 6 Summary in Finnish... References... APPENDIX : s in the proficiency test... APPENDIX : Preparation of the samples... APPENDIX : Homogeneity of the samples... 6 APPENDIX : Feedback from the proficiency test... 7 APPENDIX 5 : Evaluation of the assigned values and their uncertainties... 8 APPENDIX 6 : Terms in the results tables... APPENDIX 7 : Results of each participant... APPENDIX 8 : Summary of the z and E n scores... 6 APPENDIX 9 : s in ascending order APPENDIX : Results grouped according to the methods APPENDIX : Significant differences in the results reported using different methods... APPENDIX : Estimation of the measurement uncertainties reported by the participants.. 5 Proftest SYKE MET /8 5

8 6 Proftest SYKE MET /8

9 Introduction Proftest SYKE carried out a proficiency test (PT) for analysis of metals and mercury in waste waters and compost material to be used as fertilizer in October November 8 (MET /8). In the PT the results of Finnish laboratories providing environmental data for Finnish environmental authorities were evaluated. Additionally, other water and environmental laboratories were welcomed to participate in the proficiency test. In this PT it was also possible to test metals and nutrients from the composted sludge material to be used as fertilizer based on the national decree of the Ministry of Agriculture and Forestry / []. The measurands for the synthetic and waste water samples were: Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, V, and Zn. For the compost sample the measurands were: As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, S tot, V, and Zn. 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 standard ISO/IEC 7 [] and applying ISO 58 [] and IUPAC Technical report []. The Proftest SYKE is 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. Organizing the proficiency test. Responsibilities Organizer Proftest SYKE, Finnish Environment Institute (SYKE), Laboratory Centre Ultramariinikuja, FI Helsinki, Finland Phone: , proftest@environment.fi The responsibilities in organizing the proficiency test Mirja Leivuori coordinator Riitta Koivikko substitute for coordinator Keijo Tervonen technical assistance Markku Ilmakunnas technical assistance Sari Lanteri technical assistance Ritva Väisänen technical assistance Proftest SYKE MET /8 7

10 Cooperation partner Analytical experts Finnish Food Safety Authority, Aija Pelkonen, compost sample Timo SaraAho (SYKE): metals, IDICPMS Teemu Näykki (SYKE): Hg, IDICPMS Compost sample: Aija Pelkonen, Subcontracting Homogenization and dividing of the compost into subsamples: KVVY Tutkimus Oy, accredited by FINAS (T6, s Analytical services for the compost sample: Finnish Food Safety Authority, Research and Analytical Department accredited by FINAS (T, In total laboratories participated in this proficiency test (Appendix ), 9 participants from Finland and two from other European countries. One participant reported two sets of results. Altogether 6 % of the participants used accredited analytical methods at least for a part of the measurements. For this proficiency test, the sample testing laboratories have the codes and (SYKE, Helsinki, T, and 6 (Finnish Food Safety Authority, Research and Analytical Department, T, compost sample) in the result tables.. Samples and delivery Four types of samples were delivered to the participants: synthetic, municipal and industrial waste water as well as compost samples. 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 sample preparation is described in details in the Appendix. The synthetic sample AM was acidified with nitric acid and the synthetic mercury sample AHg with the hydrochloric acid. The samples VM and VHg were municipal waste water with additions of single element standard solutions (AccuStandard for Hg and Merck CertiPUR for other elements, Appendix ). The industrial waste water samples TM (after analysis: TN no digestion / TY digestion with acid or with acid mixture) and THg for Hg measurements were prepared with additions of single element standard solutions (AccuStandard for Hg and Merck CertiPUR for other elements, Appendix ). The tested compost sample KM (after analysis: KN digestion with HNO / KO digestion with HNO + HCl / KX other digestion) was composted sludge collected from the sewage 8 Proftest SYKE MET /8

11 treatment plant in Southern Finland. The composted sludge was freezedried and sieved to particle size of.5 mm. The sample was homogenized and divided into subsamples using a vibrating feeder distributor at the laboratory of KVVY Tutkimus Oy in Tampere. 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 days by analyzing Cd, Cu, Hg, and Zn. According to the test results all used vessels fulfilled the purity requirements. The samples were delivered on 8 October 8 to the participants abroad and on 9 October 8 to the national participants. The samples arrived to the participants mainly on October 8. The samples were requested to be measured as follows: Mercury in water samples latest on 9 October 8 The other measurands and samples latest on November 8 The results were requested to be reported latest on November 8. The participants delivered the results mainly accordingly, two participants reported their results on 5 November 8. The preliminary results were delivered to the participants via on November 8.. Homogeneity and stability studies The homogeneity of the water samples was tested by analyzing Cd, Cr, Cu, Hg, Pb, Se, and Zn. More detailed information of homogeneity study 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, and thus known to be homogenous. However, homogeneity of these was checked by parallel measurements of two samples and they were considered homogenous. Based on the earlier similar proficiency tests the water samples are known to be stable over the given time period for the test. The homogeneity of the compost sample was studied by analyzing Cu, Mn, Pb, P tot, and Zn in the laboratory of the Finnish Food Safety Authority (T, The difference of the results from the homogeneity study and the result of the organizing laboratory (SYKE and KVVY) during the test were compared to the criterion. s pt taking into account the total measurement uncertainties (data not shown). The criterion was fulfilled in each case, thus the compost sample was considered stable..5 Feedback from the proficiency test The feedback from the proficiency test is shown in Appendix. The comments from the participants mainly dealt with their result reporting errors. The comment from the provider is about the zero results. All the feedback is valuable and is exploited when improving the activities. Proftest SYKE MET /8 9

12 .6 Processing the data.6. Pretesting the data To test the normality of the data the KolmogorovSmirnov test was applied. The outliers were rejected according to the Grubbs or Hampel test before calculating the mean. The results which differed from the data more than 5 s rob or 5 % from the robust mean were rejected before the statistical results handling. If the result was reported as below detection limit, it was not included in the statistical calculations. More information about the statistical handling of the data is available from the Guide for participant [5]..6. Assigned values For the synthetic sample AM the NIST traceable calculated concentrations were used as the assigned value, with exception of Pb and Hg. The results based on isotope dilution (ID) ICP MS technique were used as assigned value for Hg and Pb in samples AM, TN, VM, AHg, THg and VHg. The assigned value based on the IDICPMS method is the mean of the homogeneity results and the test result (9 results). The IDICPMS method is accredited for soluble lead in synthetic and natural waters and for soluble mercury in synthetic, natural and waste water in the scope of calibration laboratory (K5; For the other samples and measurands either the robust mean or, when the number of reported results was low (n(stat)<), the mean or the median of the results reported by the participants was used as the assigned value (Appendix 5). If only one result was reported to the sample, the assigned value is not set (Hg, P tot : KX). The robust mean, the mean and the median are not metrologically traceable assigned values. As it was not possible to have metrologically traceable assigned values for all measurands, in those cases the robust mean, the mean or the median of the results was the best available value to be used as the assigned value. The reliability of the assigned value was statistically tested [, ]. The expanded uncertainty for the calculated assigned values (k=) was estimated using standard uncertainties associated with individual operations involved in the preparation of the sample. The main individual source of the uncertainty was the uncertainty of the concentration in the stock solution. When the robust mean, the mean or the median was used as the assigned value, the uncertainty was calculated using the robust standard deviation or standard deviation, respectively [, 5]. For the metrologically traceable mercury and lead results, the uncertainty is the expanded measurement uncertainty of the IDICPMS method. Proftest SYKE MET /8

13 The expanded uncertainty of the calculated and metrologically traceable assigned values for metals in the synthetic samples varied between. and %. When using the robust mean, the mean or the median of the participant results as the assigned value, the expanded uncertainties of the assigned values were between. and 9 % (Appendix 5). The assigned values have not been changed after reporting the preliminary results..6. Standard deviation for proficiency assessment and results evaluation The standard deviation for proficiency assessment was estimated on the basis of the uncertainty of the assigned value, the concentration of the measurand, the results of homogeneity and stability tests, and the longterm variation in the former proficiency tests. If the number of reported results was low (Hg: KC, P tot, N tot : KN) the standard deviation for proficiency assessment was not set, and the proficiency estimation was not given. The standard deviation for the proficiency assessment ( s pt, at the 95 % confidence level) was set to 5 % depending on the measurement. When the number of reported results was low and the uncertainty was set for the assigned value, the performance was estimated by means of E n scores ( Error, normalized, Appendix 8). These are used to evaluate the difference between the assigned value and participant s result within their claimed expanded uncertainty. E n scores are calculated [5]: ( ) =, where x i = participant s result, x pt = assigned value, U i = the expanded uncertainty of a participant s result and U pt = the expanded uncertainty of the assigned value. Scores of E n. < E n <. should be taken as an indicator of successful performance when the uncertainties are valid. Whereas scores E n. or E n. could indicate a need to review the uncertainty estimates, or to correct a measurement issue. When using the robust mean, the mean or the median 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 standard deviation and the corresponding was estimated by comparing the deviation for proficiency assessment (s pt ) with the robust standard deviation (s rob ) or standard deviation (s) of the reported results []. The criterion s rob (or s) / s pt <. was mainly fulfilled. Proftest SYKE MET /8

14 In the following cases, the criterion for the reliability of the assigned value and/or for the reliability of the target value for the deviation was not met and, therefore, the evaluation of the performance is weakened in this proficiency test: Sample Measurand TN Cd, Cu, TY As, Cr, Ni,, Zn KO Cd, Cr, Ni, V, Results and conclusions. Results The terms used in the result tables are show 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 results of the replicate determinations are presented in Table. The summary of the z and E n scores is shown in Appendix 8 and s in the ascending order in Appendix 9. The reported results grouped by the used analytical methods with their expanded uncertainties (k=) are presented in Appendix. The robust standard deviations of the results varied from.8 % to.7 % and the standard deviations varied from. % to. % (Table ). The robust standard deviation or the standard deviation of results was lower than % for 8 % and for % of the results, respectively. For the waste water samples the robust standard deviations of the results varied from.8 % to 9.7 % and for the compost sample the variation was from.8 % to.7 % (Table ). The robust standard deviations for waste water samples were approximately in the same range as in the previous similar proficiency test, where the deviations varied from. % to 5.5 % [6]. Proftest SYKE MET /8

15 Table. The summary of the results in the proficiency test MET /8. Measurand Sample Unit Assigned value Mean Rob. mean Median srob / s srob %/ s % x spt % n (all) Acc z % Al AM TN TY VM As AM KN mg/kg KO mg/kg TN TY VM B AM TN TY VM Ba AM TN TY VM Ca AM mg/l KN g/kg KO g/kg TN mg/l TY mg/l VM mg/l Cd AM KN mg/kg KO mg/kg TN TY VM Co AM TN TY VM Cr AM KN mg/kg KO mg/kg TN TY VM Cu AM KN mg/kg KO mg/kg TN TY VM Proftest SYKE MET /8

16 Table. The summary of the results in the proficiency test MET /8. Measurand Sample Unit Assigned value Mean Rob. mean Median srob / s srob %/ s % x spt % n (all) Acc z % Fe AM KN g/kg KO g/kg TN TY VM Hg AHg KC mg/kg..... KN mg/kg KO mg/kg KX mg/kg.. THg VHg K KN mg/kg KO mg/kg Mg AM mg/l KN mg/kg KO mg/kg TN mg/l TY mg/l VM mg/l Mn AM KN mg/kg KO mg/kg TN TY VM Mo AM KN mg/kg KO mg/kg TN TY VM Ni AM KN mg/kg KO mg/kg TN TY VM Ntot KN mg/kg 7 5. KX mg/kg Pb AM KN mg/kg KO mg/kg TN TY VM Proftest SYKE MET /8

17 Table. The summary of the results in the proficiency test MET /8. Measurand Sample Unit Assigned value Mean Rob. mean Median srob / s srob %/ s % x spt % n (all) Acc z % Ptot KN g/kg KO g/kg KX g/kg.8.8 Sb AM TN TY VM Se AM TN TY VM Sn AM TN TY VM Sr AM TN TY VM Stot AM mg/l KN mg/kg KO mg/kg TN TY VM V AM KN mg/kg KO mg/kg TN TY VM Zn AM KN mg/kg KO mg/kg TN TY VM Rob. mean: the robust mean, s rob : the robust standard deviation, s: the standard deviation, s rob %: the robust standard deviation as percent, s% : the standard deviation as percent, s p %: the total 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 /8 5

18 . Analytical methods The participants were allowed to use different analytical methods for the measurements 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. Effect of sample pretreatment on elemental concentrations in waste waters Elements in waste water were mainly measured from acidified samples without sample pretreatment with the exception of the industrial waste water sample (TN/TY). Mostly the participants measured the acidified industrial waste water without sample pretreatment (TN), and a smaller part of the participants measured the industrial waste water after acid digestion (TY). The results of these samples were evaluated separately (Table ). The difference between the average concentrations of elements measured by different sample pretreatment methods was tested using the ttest. Statistically significant difference was observed for chromium analyses. For Cr no pretreatment approach gave statistically significantly lower results compared to the pretreatment with acid digestion (Appendix ). For an unfiltered waste water sample the results are expected, acid digestion should give similar or higher results than without digestion. Effect of sample pretreatment on elemental concentrations in compost sample Elements in the compost sample were measured mainly after nitric acid digestion (KN) or after aqua regia digestion (KO). The results of these were evaluated separately (Table ). Both treatments can be considered as partial digestions. The difference between the average concentrations of elements measured by different acid digestion was tested using the ttest. Statistically significant difference was observed for Fe, Pb and S tot analyses. In both cases, nitric acid digestion gave significantly lower results compared to the aqua regia digestion approach (Appendix ). The digestion method in general can highly influence the recoveries depending on digestion temperature and hold times as can the sample weight and acid amount ratio. Effect of measurement methods on elemental results The most commonly used analytical method was ICPMS, followed by ICPOES. FAAS or GAAS technique was used by one participant for some measurements. Hydride generation ICP OES and AAS techniques were both used by one participant for some measurements (Appendix ). The difference between the average concentrations of metals measured by different measurement methods was tested using the ttest. Statistically significant differences or visual differences were not observed between the results. 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 6 Proftest SYKE MET /8

19 (e.g. GAAS analysis). It may also be caused by incorrect background correction (ICPOES) or matrix effects. 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. Effect of measurement methods on mercury results For the analysis of mercury, ICPMS was the most often used method of analysis. That was followed by CVAFS. Also some participants () reported to measure mercury with CVAAS, CVICPOES and CVICPMS technique. Also ICPOES or direct combustion (O flow + AAS) method was used by some participants for mercury analyses of the compost sample (Appendix ). For the compost sample quite few mercury results were reported, aqua regia digestion (KO) was most commonly used, followed by nitric acid digestion (KN). Two participants analysed mercury from the compost sample with direct oxygen combustion (LC, Table ). Based on the visual comparison no differences between the used measuring or digestion methods were found (Appendix ). As for the other metal determinations, also mercury results are affected by digestion procedures used (acids and oxidation reagents used, their concentration, amounts and purities, digestion temperature and time). Analytical techniques does not have so much effect on the results, but the fact is that for example using CVAFS lower detection limits can be achieved compared to CVAAS. CVICPMS technique is known to have very competent detection limits as well.. Uncertainties of the results At maximum 8 % of the participants reported the expanded uncertainties (k=) with their results for at least some of their results (Table, Appendix ). Several approaches were used for estimating the measurement uncertainty (Appendix ). The most commonly used approach was based on the method validation data or using the internal quality data in different ways [7]. MUkit measurement uncertainty software for the estimation of the uncertainties was used by at maximum five participants (Appendix ) [8]. 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 measurements and the sample types. As can be seen in Table, some of the participants have overestimated their expanded (k=) Proftest SYKE MET /8 7

20 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. In order to promote the enhancement of environmental measurements quality standards and traceability, the national quality recommendations for data entered into water quality registers have been published in Finland [9]. The recommendations for measurement uncertainties for most of the tested measurands in waste water are %. In this proficiency test some of the participants had their measurement uncertainties within these limits, while some did not achieve them. Harmonization of the uncertainties estimation should be continued. Table. The range of the expanded measurement uncertainties (k=, U i %) reported by the participants. Measurand AM/AHg % TN/THg % TY % VM/VHg % KC/KN/KO/KX % Al 5 5 As B Ba 5 5 Ca Cd 5 56 Co 7 9 Cr Cu Fe 5 Hg K 5 Mg Mn Mo Ni Ntot Pb Ptot Sb Se Sn Sr Stot V Zn Proftest SYKE MET /8

21 Evaluation of the results The evaluation of the participants was based on the z and E n scores and they were interpreted as follows: Criteria Performance z Satisfactory < z < Questionable z Unsatisfactory. < En <. Satisfactory En. or En. Unsatisfactory In total, 9 % of the results evaluated with s were satisfactory when total deviation of 5 % from the assigned value was accepted. From the results evaluated with E n scores, 7 % were satisfactory (Appendix 8). Table. Summary of the performance evaluation in the proficiency test MET /8. Sample Satisfactory results (mean, %) Accepted deviation from the assigned value (%) Remarks AM / AHg 9 / 8 Mainly good performance in the sample AM. Difficulties in measurements for B, Ca and Se, < 8% satisfactory results. In the MET /7 the performance was satisfactory for 9/75 % of the results [6]. KN / KO : 97 / 89 En score KN: 8 55 Somewhat approximate assessment for: Cd, Cr, Ni, V. Mainly good performance in the sample KN. Difficulties in measurements for Cd in the sample KO, < 8% satisfactory results. En score for Hg in the sample KO was 6 %. Due to low number of results Ptot and Ntot was not evaluated in the sample KN. TN / THg 95 / 8 5 Somewhat approximate performance evaluation for Cd, Cu. Mainly good performance in the sample TN. In the MET /7 the performance was satisfactory for 9 / 9 % of the results [6]. TY : 7 En score: 6 Somewhat approximate performance evaluation for As, Cr, Ni, Zn. Many results were evaluated based on En scores due to low number of results. In the MET /7 the performance was satisfactory based on s for 96 % of the results when accepting deviation of 55 % from the assigned value [6]. Totally the performance was remarkable lower in this PT than in the MET /7. VM / VHg 86 / 85 5 Difficulties in measurements for Pb, Se, < 8% satisfactory results. In the MET /7 the performance was satisfactory for 89 / 88 % of the results when accepting deviation of % from the assigned value [6]. Proftest SYKE MET /8 9

22 Altogether 6 % of the participants used accredited analytical methods at least for a part of the measurements and 89 % of their results were satisfactory. The summary of the performance evaluation and comparison to the previous performance is presented in Table. In the previous similar PT, Proftest SYKE MET /7, the performance was satisfactory for 9 % of the all participants when standard deviation of 5 % from the assigned values were accepted [6]. In average, the satisfactory results varied between 7 % and 95 %, based on evaluation with s, for the tested sample types (Table ). The share of satisfactory results in the synthetic sample AM was the lowest for B, about 69 %. In total the share was at the same level as in the previous similar proficiency test in 7 (Table ) [6]. For the compost sample digested with nitric acid (KN) the number of results for some measurands was low, and thus the performance was evaluated based on the E n scores (Appendix 8). For the sample KN, 8 % of the E n scores were satisfactory (Table ). Further, 97 % of the results evaluated with s were satisfactory when the deviation of 5 % from the assigned value was accepted (Table ). The compost sample results obtained after aqua regia digestion (HNO +HCl, KO) were evaluated with s and the performance was satisfactory for 97 % of the results when accepting the deviation of 5 5 % from the assigned value (Table ). For the industrial waste water sample (TN (no digestion) and THg) 88 % of the results were satisfactory, when deviation of 5 % from the assigned value was accepted (Table ). For As, Ba, Cd, Co, Cr, Fe, Mg, Mn, Se, Sr, V, and Zn in the sample TN all the results were satisfactory. For the industrial waste water sample digested with acid or with acid mixture, TY, the performance evaluation was done with s and was weaker than in the previous similar PT, Proftest SYKE MET /7 (7 % vs. 96 %, respectively, Table ) [6]. Also for the sample TY the number of results for some measurands was low, and thus the performance of those was evaluated based on the E n scores (Appendix 8). In total, 6 % of the results evaluated with E n scores were satisfactory (Table ). For the municipal waste water samples VM and VHg the number of satisfactory results was in the same level than in 7, with accepting standard deviation 5 5 % from the assigned value (Table ) [6]. 5 Summary Proftest SYKE carried out the proficiency test (PT) for analysis of elements in waste waters and compost material in October November 8 (MET /8). The measurands for the synthetic and waste water samples were: Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, V, and Zn. For the compost sample the measurands were: As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, S tot, V, and Zn. In total laboratories participated in the PT. The calculated concentration (the NIST traceable), the robust mean, the mean or the median of the results reported by the participants was chosen to be the assigned value for the measurand, Proftest SYKE MET /8

23 with the exception of Pb and Hg where the used assigned values were based on the metrologically traceable isotope dilution (ID) ICPMS technique for some samples. The uncertainty for the assigned value was estimated at the 95 % confidence level (k=) and it was between. and % for the calculated and metrologically traceable assigned values and for assigned values based on the robust mean, the mean or the median it was between. and 9 %. The evaluation of the performance was based on the z or E n scores. In total, 9 % of the results evaluated with s were satisfactory when total deviation of 5 % from the assigned value was accepted. From the results evaluated with E n scores, 7 % were satisfactory. Altogether 6 % of the participants used accredited analytical methods at least for a part of the measurements and 89 % of their results were satisfactory. 6 Summary in Finnish Proftest SYKE järjesti lokamarraskuussa 8 pätevyyskokeen laboratorioille, jotka määrittävät metalleja ja elohopeaa viemärilaitos ja teollisuusjätevesistä sekä lannoitteena käytettävästä kompostimateriaalista (MET /8). Pätevyyskokeessa määritettiin synteettisestä sekä jätevesinäytteistä testisuureet Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Mo, Ni, Pb, Sb, Se, Sn, Sr, S tot, V ja Zn. Kompostinäytteestä määritettiin testisuureet As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, N tot, Ni, P tot, Pb, S tot, V ja Zn. Pätevyyskokeeseen osallistui yhteensä laboratoriota. Testisuureen vertailuarvona käytettiin laskennallista pitoisuutta, osallistujien tulosten robustia keskiarvoa, keskiarvoa tai mediaania. Lyijylle ja elohopealle käytettiin metrologisesti jäljitettävää vertailuarvoa osassa testinäytteistä. Vertailuarvolle laskettiin epävarmuus 95 % luottamusvälillä. Vertailuarvon laajennettu epävarmuus oli, % laskennallista tai metrologisesti jäljitettävää pitoisuutta vertailuarvona käytettäessä ja muilla välillä, 9 %. Pätevyyden arviointi tehtiin z tai E n arvojen avulla. Koko aineistossa hyväksyttäviä zarvoilla arvioituja tuloksia oli 9 %, kun tulosten sallittiin poiketa vertailuarvosta 5 %. Tuloksista, jotka arvioitiin E n arvoilla, hyväksyttyjä oli 7 %. Noin 6 % osallistujista käytti akkreditoituja määritysmenetelmiä ja näistä tuloksista oli hyväksyttäviä 89 %. Proftest SYKE MET /8

24 REFERENCES. Ministry of Agriculture and Forestry,, Decree of the Ministry of Agriculture and Forestry on Fertiliser Products /. (In Finnish). lannoitevalmisteasetus_en.pdf/c9d57 beb5ca5ecdf6ca/mmma lannoitevalmisteasetus_en.pdf.pdf (In English).. SFSEN ISO/IEC 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: ECE96D8C%7D/ Leivuori, M., Koivikko, R., SaraAho, T., Näykki, T., Tervonen, K., Lanteri, S., Väisänen, R. and Ilmakunnas, M. Interlaboratory Proficiency Test /7: Metals in waste waters and sludge. Reports of the Finnish Environment Institute 7/8. pp Magnusson B., Näykki T., Hovind H., Krysell M., Sahlin E., 7. Handbook for Calculation of Measurement Uncertainty in Environmental Laboratories. Nordtest Report TR 57 (ed. ). ( 8. Näykki, T., Virtanen, A. and Leito, I.,. Software support for the Nordtest method of measurement uncertainty evaluation. Accred. Qual. Assur. 7: 66. MUkit website: 9. Näykki, T. and Väisänen, T. (Eds.) 6. Laatusuositukset ympäristöhallinnon vedenlaaturekistereihin vietävälle tiedolle: Vesistä tehtävien analyyttien määritysrajat, mittausepävarmuudet sekä säilytysajat ja tavat.. uudistettu painos. (Quality recommendations for data entered into the environmental administration s water quality registers: Quantification limits, measurement uncertainties, strorage times and methods associated with analytes determined from waters). Suomen ympäristökeskuksen raportteja /6. 57 pp. (In Finnish). Proftest SYKE MET /8

25 APPENDIX (/) APPENDIX : s in the proficiency test Country Finland Boliden Harjavalta Oy Boliden Kokkola Oy Eurofins Ahma Oy, Oulu Eurofins Environment Testing Finland Oy, Lahti Finnish Food Security Authority, Laboratory and Research Fortum Waste Solutions Oy, Riihimäki Freeport Cobalt Oy Hortilab Ab Oy KVVY Tutkimus Oy, Tampere Kymen Ympäristölaboratorio Oy LounaisSuomen vesi ja ympäristötutkimus Oy, Turku MetropoliLab Oy Norilsk Nickel Harjavalta Oy Outokumpu Stainless Oy, Tutkimuskeskus, Tornio SGS Finland Oy, Kotka SSAB Europe Raahe, Raahe SYKE, Helsingin toimipaikka SYNLAB Analytics & Services Finland Oy UPM Tutkimuskeskus, Lappeenranta Luxembourg Laboratoire National de Sante Sweden INOVYN Sverige Ab Proftest SYKE MET /8

26 APPENDIX (/) APPENDIX : Preparation of the samples The synthetic sample AM was prepared by diluting the NIST traceable certified reference material produced by Inorganic Ventures. The synthetic sample AHg was prepared by diluting the NIST traceable AccuTrace TM Reference Standard produced by AccuStandard, Inc. The water samples VM, TM (TN/TY), VHg and THg were prepared by adding some separate metal solutions (Merck CertiPUR or AccuStandard) into the original water sample, if the original concentration was not high enough. The compost sample KM (KN/KO/KX) was composted sewage treatment plant sludge collected from southern Finland. Al As B Ba Ca Cd Co Cr 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 AM VM TN/TY 975/8 /6 9 6/8./ / /5.5./ /8.6 KN/KO/ KX mg/kg 7.6/7.8/ g/kg.8/.7/.9.89/.85/./5.5/ Cu Fe K Mg Mn Mo Ni Ntot 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 AM VM TN/TY.7/. 5 75/7 / 59/ / /6.9 KN/KO/ KX mg/kg 9 /9/ g/kg 5// /95/ 8 /985/ 75 6/5/ not meas. 5./5.75/./7. g/kg //.5 Proftest SYKE MET /8

27 APPENDIX (/) Pb Ptot Sb Se Sn Sr 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 AM Original = the original concentration Dilution = the ratio of dilution Addition = the addition concentration Ass. value = the assigned value VM TN/TY / /57..6./. 5.5/5.9 6/ KN/KO/ KX mg/kg 5 6./.7. g/kg././ Stot Measurand Original Dilution Addition Ass. value V Original Dilution Addition Ass. value Zn Original Dilution Addition Ass. value Measurand Hg Original Dilution Addition Ass. value AM 55 5,5 AHg.5.5 VM 97.8, 9 9 VHg..8 TN/TY 6 67 / ,9/6,6 5 / THg..8.8 KN/KO/ KX mg/kg / 9/ not meas.,6/,6/ 56 6/57 KN/KO/ KX/KC mg/kg.5.9/./ /. Proftest SYKE MET /8 5

28 APPENDIX (/) APPENDIX : Homogeneity of the samples Homogeneity was tested from duplicate measurements of selected measurands from three to five (n) samples of each sample type (see table below). Criteria for homogeneity s anal /s h <.5 and s sam <c, where s h = standard deviation for testing of homogeneity s anal = analytical deviation, standard deviation of the results within sub samples s sam = betweensample deviation, standard deviation of the results between sub samples c = F s all + F s anal, where s all = (. s h ) Measurement/ sample F and F are constants of F distribution derived from the standard statistical tables for the tested number of samples [, ]. Concentration [] [mg/kg] [g/kg] n spt % sh% sh sanal sanal/sh Is sanal/sh<.5? Cd/VM Yes.6. Yes Cr/VM Yes.8. Yes Cu/VM Yes. Yes Se/VM Yes. Yes Zn/VM Yes.99 Yes Cd/TM Yes.. Yes Cr/TM Yes.6. Yes Cu/TM Yes..5 Yes Se/TM Yes.. Yes Zn/TM Yes..7 Yes Cu/KM Yes.5 Yes Mn/KM Yes 96.8 Yes Pb/KM Yes.6. Yes Ptot/KM Yes.6 Yes Zn/KM Yes Yes Hg/VHg* Yes.. Yes Hg/THg*.8.. Yes.. Yes Pb/VM* Yes. Yes Pb/TM* Yes. Yes *) result based on the IDICPMS measurement ssam c Is ssam <c? Conclusion: The criteria were fulfilled for the tested measurands and the samples were regarded as homogenous. 6 Proftest SYKE MET /8

29 APPENDIX (/) APPENDIX : Feedback from the proficiency test FEEDBACK FROM THE PARTICIPANTS Comments on technical excecution Action / Proftest SYKE All In the registration the measurands were not correct on the electronic client interface (ProftestWEB) for the compost sample. The provider corrected the mistake after the participant s note. Comments to the results Action / Proftest SYKE 9 The participant reported laboratory s results erroneously for the samples TY and VM (vice versa). The result for S tot in the sample AM reported in the wrong unit. The corrected result was: Sample AM:. mg/l. The results were outliers in the statistical treatment, and thus did not affect the performance evaluation. If the results had been reported correctly, the results would have been satisfactory based on evaluation with, with the exception of questionable result for Sn in the sample VM. The participant can recalculate the z and E n scores according to the Guide for participants [5]. FEEDBACK TO THE PARTICIPANTS Comments The participant reported zero value results for Hg in the water samples. These results were treated as outliers in the statistical result handling. In the analytical measurements there is always a detection limit. Thus, the correct way to inform these low values is to report result as lower than or equal to detection limit. The provider strongly recommends participant to update the reporting procedure for low concentration results. Proftest SYKE MET /8 7

30 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 85.5 Calculated value.5 TN 975. Robust mean.8 TY Median VM Robust mean.9 As AM Calculated value.8 KN mg/kg Median KO mg/kg Mean. TN. Robust mean.7 TY Median. VM.7.5. Mean. B AM Calculated value. TN Mean. TY 8. Median VM Mean. Ba AM Calculated value.5 TN...7 Median.5 TY Median VM Mean. Ca AM mg/l... Calculated value. KN g/kg.8.. Mean.8 KO g/kg Mean. TN mg/l Mean.7 TY mg/l Median VM mg/l.9.7. Median. Cd AM Calculated value.5 KN mg/kg Median KO mg/kg Median.9 TN Robust mean. TY Mean. VM...8 Robust mean. Co AM Calculated value.6 TN..5.8 Mean. TY Median VM Robust mean.7 Cr AM Calculated value.7 KN mg/kg Median KO mg/kg Median.7 TN Robust mean. TY Mean. VM Robust mean. Cu AM Calculated value.5 KN mg/kg Mean. KO mg/kg 9. Mean.5 TN Mean.5 TY..7. Median VM Mean. 8 Proftest SYKE MET /8

31 APPENDIX 5 (/) Measurand Sample Unit Assigned value Upt Upt, % Evaluation method of assigned value upt/spt Fe AM Calculated value.6 KN g/kg 5 9. Median KO g/kg. Mean.5 TN Robust mean.5 TY Mean.5 VM Robust mean.9 Hg AHg.5.. IDICPMS.5 KC mg/kg. Median KN mg/kg Median KO mg/kg Median THg.8.5. IDICPMS.5 VHg.8.9. IDICPMS.5 K KN mg/kg Median KO mg/kg Mean.5 Mg AM mg/l...6 Calculated value.6 KN mg/kg 8.5 Median. KO mg/kg Mean.6 TN mg/l..6.5 Mean.5 TY mg/l Median VM mg/l Robust mean.9 Mn AM Calculated value. KN mg/kg 6 5. Mean.5 KO mg/kg 5 5. Mean.6 TN Robust mean.6 TY 57.5 Median VM Robust mean. Mo AM Calculated value.6 KN mg/kg Median KO mg/kg Mean. TN Robust mean.9 TY Median VM 6... Mean. Ni AM Calculated value.5 KN mg/kg... Median KO mg/kg Mean.9 TN Robust mean. TY Mean.6 VM.5.. Mean. Ntot KN mg/kg Mean KX mg/kg Median. Pb AM IDICPMS.5 KN mg/kg Median KO mg/kg Mean. TN IDICPMS.7 TY Mean. VM IDICPMS.7 Ptot KN g/kg..7. Median KO g/kg...9 Median.6 Proftest SYKE MET /8 9

32 APPENDIX 5 (/) Measurand Sample Unit Assigned value Upt Upt, % Evaluation method of assigned value upt/spt Sb AM Calculated value.7 TN Mean. TY Median VM Mean.7 Se AM Calculated value.6 TN... Mean.8 TY Median VM 5... Median.5 Sn AM.5..6 Calculated value.6 TN Median. TY Median VM.55.. Mean. Sr AM Calculated value.6 TN 6 5. Mean.6 TY 5.8 Median VM Mean.5 Stot AM mg/l...5 Calculated value.5 KN mg/kg Median KO mg/kg 9. Median.9 TN Median. TY Median VM Median. V AM Calculated value.6 KN mg/kg.6.. Median KO mg/kg.6.8. Median.8 TN Median.9 TY Median VM Median. Zn AM.6 Calculated value.6 KN mg/kg Median. KO mg/kg Median. TN 7 5. Robust mean.5 TY 8. Median. VM 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= the standard deviation for proficiency assessment u pt= the standard uncertainty of the assigned value If u pt/s pt <., the assigned value is reliable and the s are qualified. Proftest SYKE MET /8