Analytische Qualitätssicherung Baden-Württemberg

Transcription

1 Analytische Qualitätssicherung Baden-Württemberg Proficiency Test /1 - TW S7 Trifluoroacetic acid in drinking water - Trifluoroacetic acid (TFA) Final report provided by AQS Baden-Württemberg at Institute for Sanitary Engineering, Water Quality and Solid Waste Management, University of Stuttgart Bandtäle, 79 Stuttgart-Büsnau, Germany And IWW Water Center Moritzstr., 7 Mülheim an der Ruhr, Germany Stuttgart, in September 1

2 AQS Baden-Württemberg at Institute of Sanitary Engineering, Water Quality and Solid Waste Management at University of Stuttgart Bandtäle 79 Stuttgart-Büsnau Germany Tel.: +9 ()711 / - Fax: +9 ()711 / info@aqsbw.de Responsibilities: Scientific director: PT coordinator: Assistant PT coordinator Sample preparation Dr.-Ing. Michael Koch Dr.-Ing. Frank Baumeister Dipl.-Biol. Biljana Marić Dr. Peter Balsaa (IWW) Release of the report: Dr.-Ing. Michael Koch on.9.1 Version of the report 1

3 List of contens List of contents 1. General PT design Sample preparation Sample distribution Analytical methods Submission of the results Basic principle of evaluation and assessment.... Evaluation Explanation for the appendices.... Measurement uncertainty Traceable reference values Internet... Appendix A TFA 1... A-1 Appendix B Appendix C TFA 1... C-1

4 PT /1 TW S 7 TFA Page 1 of 1. General This PT was provided by AQS Baden-Württemberg in cooperation with IWW Water Center in Mülheim an der Ruhr and with the network NORMAN (Network of reference laboratories for monitoring of emerging environmental pollutants). The following parameter was offered: Trifluoracetic acid (TFA); CAS-No.: 7--1 The PT was executed and evaluated according to the requirements of DIN -A and ISO/TS 1.. PT design Each participant received the following samples: samples for the determination of TFA in -ml-plastic tubes. different concentration levels/batches were produced. All participants received the same samples.. Sample preparation The samples for the determination of TFA were based on a real ground water matrix from the northern part of the region Ruhr in North Rhine-Westphalia. The ground water was used without treatment for the sample preparation. The ground water was spiked with stock solutions and the concentrations covered drinking and ground water relevant ranges.. Sample distribution The samples were dispatched on June 1 by express service. Analytical methods The participants were free to choose a suitable method, but a limit of quantification of. µg/l was required. The participants were informed that the samples had to be analysed in the own laboratory, with own personal and own equipment. Subcontracting of the analysis was not allowed. The participants were informed to cool the samples after receipt and to start with the analysis one day after receipt at the latest.

5 PT /1 TW S 7 TFA Page of The samples had to be analysed in duplicate over the complete method (sample preparation and measurement). The participants were asked to report the results as average means from both determinations in µg/l with three significant digits.. Submission of the results The deadline for the submission of results was on June Basic principle of evaluation and assessment The basic principle of the evaluation and assessment of the PTs from AQS Baden-Württemberg are described in the document Evaluation of the PTs and information for the report, which can be downloaded from This PT was evaluated as follows: Assigned value xpt: Standard deviation for proficiency Q method assessment σpt: Upper limit of σpt: % Lower limit of σpt: % Reference value Consensus value (Hampel estimator) Assessment: zu-score Classification of the single results: zu. successful. < zu <. questionable zu. unsatisfactory Parameter assessment: A parameter was assessed as successful, if more than half of the values were correctly determined ( out of values are within the tolerance limits).

6 PT /1 TW S 7 TFA Page of. Evaluation Number of participants: 9 laboratories did not report any results Number of reported values Number of accepted values: 9 (9, %) Illustration of the susccessful and not successful laboratories for each parameter 9. Explanation for the appendices The explanations for the appendices can be found in the document Evaluation of the PTs and information for the report, which can be downloaded from Measurement uncertainty General: Number of labs with valid values Number of labs with valid values and 1 (,7 %) reported measurement uncertainties Number of valid values Number of valid values with measurement (,7 %) uncertainties

7 PT /1 TW S 7 TFA Page of Measurement uncertainties against the accreditation status Accreditation status of the Number of Number of values with values values measurement uncertainty accredited 7 ( %) not accredited 1 (,7 %) not specified 1 ( %) Interpretation of the reported measurement uncertainties: If measurement uncertainties are underestimated values assessed as satisfactory in the PT ( zu ), will have a large ζ -score. ζ > means that the own requirements (defined in terms of estimated uncertainty) are not fulfilled. Number of values with reported measurement uncertainty having a zu, Number of values with a magnitude of -scores > The own requirements of the laboratory are not fulfilled and the estimation of the measurement uncertainty is too low (1 %) 11. Traceable reference values The explanations about traceable reference values can be found in the document Evaluation of the PTs and information for the report, which can be downloaded from 1. Internet The report is available on the following webpage:

8 PT /1 - TW S7 trifluoroacetic acid level assigned value [µg/l] expanded uncertainty of the assigned value [%] standard deviation, calculated using robust statistics [µg/l] standard deviation for proficiency assessment [µg/l] standard deviation for proficiency assessment [%] 1,,9,1,1, 1,1,7 1,1-1, 1,,1,7,, 1,, 1,7,1 -,1 1, 1,,7 1,9 1,9 11, 1,91 9,,7-1,9 1 1,7 sum 9,7 upper tolerance limit [µg/l] lower tolerance limit [µg/l] upper tolerance limit [%] lower tolerance limit [%] number of results out below out above out [%] Recovery and matrix content 1 trifluoroacetic acid 1 mean in µg/l 1 1 added amount in µg/l slope of the regression: 1,; average recovery:, % page A-1 of A-

9 PT /1 - TW S7 Relative standard deviation and tolerance limits trifluoroacetic acid rel. standard deviation in % concentration in µg/l The relative standard deviations calculated with the Q-method did not reach the limits. trifluoroacetic acid tolerance limits in % concentration in µg/l page A- of A-

10 PT /1 - TW S7 Method specific evaluation used methods for trifluoroacetic acid 7 71, percentage 1,9 11,, LC-MS-direct injection GC-MS-derivatisation Others IC-MS-direct injection method comparison trifluoroacetic acid 9 frequency in % 7 too low low correct high too high Others GC-MS-derivatisation LC-MS-direct injection The values determined with GC-MS-derivatisation showed a slightly broader distribution. page A- of A-

11 PT /1 - TW S7 Comparison of means and reference values level mean [µg/l] exp. uncertainty [µg/l] exp. uncertainty [%] reference value [µg/l] exp. uncertainty [µg/l] exp. uncertainty [%] 1,,7 9,,,1,1,,1,,1,,1 1,,7, 1,7,,1 comparison of means and reference values overall mean reference values LC-MS-direct injection mean in µg/l 1,9,,7,,,,,,1 1 level page A- of A-

12 PT /1 - TW S7 comparison of means and reference values overall mean reference values LC-MS-direct injection, mean in µg/l 1, 1, level comparison of means and reference values overall mean reference values LC-MS-direct injection 1 1 mean in µg/l level page A- of A-

13 PT /1 - TW S7 rel. standard dev. method specific rel. standard dev. in % 1 1 level overall mean LC-MS-direct injection LC-MS-direct injection level robust mean [µg/l] exp. unc. of the mean [µg/l] exp. unc. of the mean [%] robust standard deviation [µg/l] 1,79,,,17 1,,11,7,977, 1,1 19, 1,,77 1,99, 1 robust standard deviation [%] number of results out below out above out [%] page A- of A-

14 PT /1 - TW S7 % 9% trifluoroacetic acid - exp. measurement uncertainty 17 % 1 % 1 % exp. measurement uncertainty % 7% % % % % % % % page B-1 of B-1

15 PT /1 - TW S7 PT /1 - TW S7 assigned value [µg/l]* upper tolerance limit [µg/l] trifluoroacetic acid - 1, ±,1 1,1 lower tolerance limit [µg/l],7 result [µg/l] ± z-score z U -score assessm.** 1,,,9 1,9 s,9 -,7 s 1,,9 q,,1,, s,9 -,7 s 7,97, s,7, -, -, s 9,777 -, s 17, 1, 77,7 u 11,9, s 1,, -, -,7 s 1,9, s 1,9, s 1,97,1,, s 1,7, -,7 -, q 19,11, s, 11, -,9 s 1,79, -1, -, s 1,1,97,1 1, s,79 -,1 s 9,91, s 1, -,7 s,1,9 -, -1, s,, s,7 -, q 7,1, -, -1,1 s 9,97,7 s 1,,,, q 1,71 -, s,779 -, s,, s,7,,1, s 7,, -, -1, s,9 -,7 s 9,,11,, s * The stated uncertainty of the assigned value is the expanded uncertainty with a coverage factor k= corresponding to a confidence level of about 9% ** s = satisfactory, q = questionable, u = unsatisfactory page C-1 of C-9

16 PT /1 - TW S7 trifluoroacetic acid , concentration in µg/l 1, 1, trifluoroacetic acid ,7 1 z U -score page C- of C-9

17 PT /1 - TW S7 trifluoroacetic acid , expanded uncertainty in µg/l, 1, 1, trifluoroacetic acid - 1 z-score page C- of C-9

18 PT /1 - TW S7 PT /1 - TW S7 assigned value [µg/l]* upper tolerance limit [µg/l] trifluoroacetic acid -,1 ±,, lower tolerance limit [µg/l] 1,7 result [µg/l] ± z-score z U -score assessm.**,1,7 1,7 1, s, -1, s,, s,,1,, s 1,9-1, s 7, 1, s,,17 -, -, s 9, -, s,,1,9, q 11,, s 1,, -, -,9 s 1,, s 1,7,7 s 1, 1,1,1,1 s 1 1,, -,7-1, s 19, -, s,1 1, -, s 1,,71,, s,77,79 1,,9 s,, s 9, 1, s 1,99 -, u,1, -1,7 -, s,7,1 s,9,1 u 7 1,91,19 -,1-1, s 9,, s,, 1,, s 1,, s,, s,, s,,,1, s 7,,,1, s,, s 9,,9,7, s * The stated uncertainty of the assigned value is the expanded uncertainty with a coverage factor k= corresponding to a confidence level of about 9% ** s = satisfactory, q = questionable, u = unsatisfactory page C- of C-9

19 PT /1 - TW S7 trifluoroacetic acid - concentration in µg/l trifluoroacetic acid - z U -score page C- of C-9

20 PT /1 - TW S7 1 trifluoroacetic acid - expanded uncertainty in µg/l trifluoroacetic acid - z-score page C- of C-9

21 PT /1 - TW S7 PT /1 - TW S7 assigned value [µg/l]* upper tolerance limit [µg/l] trifluoroacetic acid - 1, ±, 1,91 lower tolerance limit [µg/l] 9, result [µg/l] ± z-score z U -score assessm.** 1,,9,, s 11,9 -,1 s 1,, s 11,,9 -, -, s 11, -, s 7 1,, u 11,9 1,97 -, -,1 s 9 11, -, s 1,1,17-7, -, u 11 1,7 s 1,9 1, -,9-1, s 1 11, -, s 1 1,,1 s 1 11,1 -, -, s 1 11,1 1, -1, -, s , s 9, 1 -, -1,7 s 1 1,9,7,, s 1,,1,, s, -1, s 9 1,7 s 1, -1,1 s 1, 1,9,, s 11,9 -,1 s 1,, s 7,7 1,1 -, -1,1 s 9 1, 1, s 1,, 1, 1, s 1 1,7 1, s 1,, s 1,, s 1,,,, s 7 1,7 1,, 1, s, -1, s 9 11,7 1,7 -, -, s * The stated uncertainty of the assigned value is the expanded uncertainty with a coverage factor k= corresponding to a confidence level of about 9% ** s = satisfactory, q = questionable, u = unsatisfactory page C-7 of C-9

22 PT /1 - TW S7 trifluoroacetic acid concentration in µg/l trifluoroacetic acid - z U -score page C- of C-9

23 PT /1 - TW S7 1 trifluoroacetic acid - expanded uncertainty in µg/l trifluoroacetic acid - z-score , page C-9 of C-9