Proficiency test SPIL-1 (2014) Organic matter, phosphorus, chloride, sulphate and suspended matter in wastewater (effluent)

Transcription

1 Proficiency test SPIL-1 (2014) Organic matter, phosphorus, chloride, sulphate and suspended matter in wastewater (effluent) Quality Documentation May 2014

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3 Proficiency test SPIL-1 (2014) Quality Documentation May 2014 Eurofins Miljø A/S Smedeskovvej 38 DK-8464 Galten Denmark Tlf: Fax: Web: Client Client s representative Environmental laboratories Project Project No Proficiency test SPIL-1 (2014) Authors Maj-Britt Fruekilde Date Approved by Stine Kjær Ottsen Quality Documentation Report MBF SJN Revision Description By Approved Date Key words Analytical quality, assigned value, precision, trueness, homogenity, stability, COD, BOD5 (w. ATU), NVOC/TOC, total phosphorus, chloride, sulphate, suspended matter, wastewater Classification Open Internal Proprietary Distribution DANAK Eurofins: Maj-Britt Fruekilde, Stine Kjær Ottsen

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5 CONTENTS 1 INTRODUCTION FEATURES OF THE PROFICIENCY TEST Sample preparation Statistical analysis of participants data Assigned and spike value Assigned and spike values Test of spike values Test of assigned values HOMOGENEITY AND STABILITY OF SAMPLES CONCLUSION REFERENCES... 7 ANNEX A LIST OF PARTICIPANTS ANNEX B SAMPLE PREPARATION ANNEX C CONTROL OF SPIKE VALUES ANNEX D CONTROL OF RECOVERY ANNEX E CONCENTRATION LEVEL ANNEX F HOMOGENEITY AND STABILITY... 32

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7 1 INTRODUCTION A proficiency test on the analysis of organic matter, phosphorus, chloride, sulphate and suspended matter in wastewater was conducted on 13 March The proficiency test was organised by Eurofins Miljø A/S. The present report contains Eurofins documentation for the quality of the proficiency test. Results of the proficiency test including data from participating laboratories and statistical analysis of these data were issued in a report to all participants /1/ on 10 April

8 2 FEATURES OF THE PROFICIENCY TEST Participants in the proficiency test were a total of 72 laboratories from Denmark, Norway and Sweden. Some laboratories participated with more than one participant. One of the registered laboratories did not submit results. A list of participants is shown in Appendix A. The closing date for submission of results was 27 March All participants had submitted their results before the dead-line. 2.1 Sample preparation The parameters covered in the proficiency test are listed in Table 2 as are the abbreviations used in this report. Eight samples were dispatched for the proficiency test. The samples were sample pairs covering the parameters as described in Table 1. The matrix of the samples represented wastewater, in this case effluent. Sample preparation is described in Appendix B. Table 1 Samples in the proficiency test Sample name Parameters A1/B1 COD Cr /NVOC COD Cr, NVOC A1/B1 BOD BOD 5, BOD 7 A2/B2 TP, Cl, SO 4 A3/B3 TSS 2.2 Statistical analysis of participants data A split-level design was used. The data analysis was performed in accordance with ISO 5725: Accuracy (trueness and precision) of measurement methods and results (1994) /2/ and as described in detail in Spliid (1992) /3/. A short introduction to the statistics and a list of symbols and abbreviations used is given in Eurofins document Schedule for a proficiency test, which is available at Eurofins home page /4/. The statistical model used is based on the assumption that the variances for the two samples in a sample pair are identical. The assumption was tested (F-test, 95% confidence level) and the result was that the two variances may be assumed to be identical for all parameters. 2.3 Assigned and spike value An overview of the concentrations in the samples (the assigned values) and the difference in concentration between the two samples of a sample pair (spike value) are shown in Table 2 compared to the range of concentrations normally encountered in effluent. The table also gives the expanded uncertainty of the assigned values. 2

9 Table 2 Assigned and spike value Parameter Abbreviation Unit Typical Range Assigned value Uncertainty of assigned value Spike value Chemical oxygen demand COD Cr mg/l O Five days biochemical BOD 5 (w. ATU) mg/l O oxygen demand Seven days biochemical oxygen demand BOD 7 (w. ATU) mg/l O Non-volatile/total organic NVOC/TOC mg/l C carbon Total phosphorus TP mg/l P Chloride Cl mg/l Sulphate SO4 mg/l Suspended matter TSS mg/l Assigned and spike values The content of each parameter in each sample is given an assigned value for the sample with the lower content and a spike value, the spike value being the difference in concentration between the two samples of the sample pair. In order to ensure optimal use of the data, the assigned value is calculated as the average of the median for both samples in the sample pair after subtraction of the spike value. The spike values are calculated from sample preparation. The assigned values for all parameters except Cl and SO 4 are operationally defined and are consensus values based upon the median for method no. 6, 76, 76A 77, 77A 91, 92 (COD Cr ), method no. 1 (NVOC), method no. 1 and 2 (TP), or method no. 2 (TSS), which are the methods required by the Danish EPA /5/. Assigned values for BOD are based upon standardised methods (method no. 1-4). A list of method identification numbers is found in the report to participants /1/. Assigned values for Cl and SO 4 are consensus values for all laboratories based on the median. The number of significant figures of the spike and assigned values are determined by the uncertainty of the assigned value: The first decimal place of the uncertainty being the last decimal place of the spike and assigned values. The uncertainty of the assigned value for NVOC is 1.2, indicating that the spike value and the assigned value should be specified as an integer. However, the spike value for NVOC is designed to 1.5, and rounding the spike value to either 1 or 2 will introduce significance on both the spike value and the assigned value. Hence the assigned value and the spike value for NVOC are given with one decimal Test of spike values A comparison was made (t-test, 95% confidence level) between the spike value and the difference in concentration between the two samples in the sample pair found from the laboratories results, see Appendix C. The test showed no significant difference between the two for most parameters. The test revealed a significant difference between the two for TP. However, the difference is numerically small and has insignificant influence on the general quality of analyses estimated from the data as well as on the evaluation of accuracy of participating laboratories. 3

10 2.3.3 Test of assigned values The assigned value and the average of the results obtained from all laboratories were also compared (t-test, 95% confidence level), see Appendix D. The test showed no significant difference between the two and the control of assigned value at Eurofins confirmed the value (Appendix E). 4

11 3 HOMOGENEITY AND STABILITY OF SAMPLES The homogeneity and stability of samples were tested using the following parameters as indicators: NVOC TP TSS Homogeneity test Combined homogeneity and stability test Combined homogeneity and stability test The results of control measurements are shown in Appendix F. The appendix also gives the results of the statistical evaluation of the control data. The data are analysed by analysis of variance (ANOVA) giving: 1. the standard deviation/variance for replicates (the contribution from analytical variability), 2. the between bottle standard deviation/variance (the contribution from heterogeneity) and 3. the between days concentration difference (the contribution from instability). Homogeneity is evaluated by comparing the between bottle variance to 0.3 * the standard deviation for evaluation of participants performance ( ) specified by the Danish EPA /5/, whereas the stability is evaluated by comparing the concentration change of the samples to. This test ensures that heterogeneity and instability will not have negative influence on the evaluation of participant performance /6/. The appendix also shows the standard deviation within and between laboratories from the proficiency test to allow comparison between tests performed and average quality from participating laboratories. The tests for stability and homogeneity show that the samples are stable and homogeneous. 5

12 4 CONCLUSION The quality control performed, including test of sample stability and homogeneity as well as test of recovery of spike and assigned values, shows that the samples and their assigned values are suitable for testing the proficiency of the participating laboratories for all parameters. The results are also suitable for estimation of the general quality of analyses among all participating laboratories. For TP the participants could not recover the spike value. The difference between the calculated spike value and that found by the participants is small and the influence on evaluation of participant performance or estimation of general quality of analyses is insignificant. 6

13 5 REFERENCES /1/ Eurofins A/S, Proficiency test SPIL-1 (2014), Report to participants, April /2/ ISO , Accuracy (trueness and precision) of measurement methods and results Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method, /3/ Spliid, H., Procedure and analysis of data for proficiency tests and environmental analyses, Report to Danish Environmental Protection Agency, 1994 (in Danish). /4/ Eurofins A/S, Schedule for a proficiency test, document may be downloaded from /5/ Ministry of Environment regulation no. 231 on quality criteria for environmental measurements, 5 March 2014 (in Danish). /6/ ISO 13528, Statistical methods for use in proficiency testing by interlaboratory comparison,

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15 9 A N N E X E S

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17 ANNEX A LIST OF PARTICIPANTS Laboratory Town Country AquaDjurs - Fornæs Renseanlæg Grenaa Denmark Bjergmarken R/A, Roskilde Forsyning Roskilde Denmark CP Kelco ApS, Spildevandslaboratoriet Ll. Skensved Denmark Esbjerg Forsyning Spildevandslaboratorium Esbjerg Denmark Esbjerg Forsyning Spildevandslaboratorium Esbjerg Denmark Eurofins Miljø A/S Vejen Denmark Faxe Forsyning Faxe Denmark Faxe Forsyning Faxe Denmark FORCE LabVest Holstebro Denmark Greve Solrød Forsyning Greve Denmark Halsnæs Kommunale Forsyning A/S Liseleje Denmark Hedensted Spildevand A/S Daugård Denmark Hedensted Spildevand A/S Daugård Denmark Hillerød Forsyning Spildevand A/S Hillerød Denmark Holstebro Centralrenseanlæg, Vestforsyning A/S Holstebro Denmark Kerteminde Forsyning - Spildevand A/S Kerteminde Denmark Kolding Spildevand A/S Bjert Denmark Køge-Egnens Renseanlæg Køge Denmark Mølleåværkets Driftslaboratorium Lyngby Denmark Nyborg Renseanlæg Nyborg Denmark Næstved Centralrenseanlæg Næstved Denmark Provas Haderslev Forsyningsservice A/S Haderslev Denmark Randers Spildevand A/S Randers NØ Denmark Ringkøbing-Skjern Forsyning A/S, Spildevand Skjern Denmark Ringsted Renseanlæg Ringsted Denmark Rønne Renseanlæg Rønne Denmark SK Forsyning, Slagelse Renseanlæg Slagelse Denmark SK Forsyning, Slagelse Renseanlæg Slagelse Denmark SK Forsyning, Slagelse Renseanlæg Slagelse Denmark SK Forsyning, Slagelse Renseanlæg Slagelse Denmark SK Forsyning, Slagelse Renseanlæg Slagelse Denmark Svendborg Centralrenseanlæg Skårup Fyn Denmark Sønderborg Forsyning Sønderborg Denmark Vandrens - Stigsnæs Industripark A/S Skælskør Denmark Vejle Spildevand A/S Vejle Denmark Vores Rens Lynettefællesskabet A/S København K Denmark Eurofins Environment Testing Norway AS Moss Norway AB Borlänge Energi, Reningsverket Borlänge Sweden AB Lennart Månsson International Helsingborg Sweden Akzo Nobel Functional Chemicals AB Cellulosic Specialties QHSE Örnsköldsvik Sweden Ernemar Laboratoriet Oskarshamn Sweden Eurofins Environment Testing Sweden AB Lidköping Sweden Fiskeby Board AB Norrköping Sweden GRYAAB AB Göteborg Sweden Holmen Paper Norrköping Sweden Holmen Paper AB Hallstavik Sweden Iggesund Paperboard, Cell & Miljölab Iggesund Sweden Ineos Sweden AB Stenungsund Sweden 11

18 Laboratory Town Country Kalmar Vatten AB, VA-lab, Avloppsreningsverket Kalmar Sweden Kristianstad Kommun Kristianstad Sweden Käppalaverket Lidingö Sweden MittSweden Vatten AB, Fillanverket lab. Sundsvall Sweden Mjölby Kommun Mjölby Sweden Motala Kommun Motala Sweden Nordic Sugar Eslöv Sweden NSVA/Öresundsverket Helsingborg Sweden Perstorp Oxo AB Stenungsund Sweden Preem AB Göteborg Göteborg Sweden Preemraff Lysekil Lysekil Sweden Reningsverket Aggerud Karlskoga Sweden Rottneros Bruk AB Rottneros Sweden SAKAB AB Kumla Sweden Smurfit Kappa Kraftliner Piteå Sweden St1 Refinery AB Göteborg Sweden Stora Enso Printing and Reading Hyltebruk Sweden Södra Cell AB Mönsterås Mönsterås Sweden Södra Cell AB, Värö Väröbacka Sweden Tekniska förvaltningen, Verksamhetsstöd VA, Laboratoriet Örebro Sweden Uddebo Laboratorium Luleå Sweden Vallviks Bruk AB Vallvik Sweden VIVAB Varberg Sweden Västerviks Miljö & Energi AB, Vattenlaboratoriet Västervik Sweden 12

19 ANNEX B SAMPLE PREPARATION Stock solution Prepared from Concentration Concentrate A g D-glucose COD Cr : g/kg g L-glutamic acid milli-q water up to kg NVOC: g/kg BOD: g/kg Concentrate B g D-glucose g L-glutamic acid milli-q water up to kg Stock TP g Na-B.glycerophosphate milli-q water up to g Stock Cl g Sodium chloride (NaCl) milli-q water up to g Stock SO g Sodium sulphate (Na 2 SO 4 ) milli-q water up to g Stock TSS g Microcrystalline cellulose milli-q water up to g COD Cr : g/kg NVOC: g/kg BOD: 1.292g/kg TP: mg/kg Cl: g/kg SO4: g/kg TSS: g/kg 13

20 Sample Sample prepared from COD Cr mg/l O 2 A1- At the laboratory 1.00 ml of concentrate COD/NVOC A1 is diluted up to ml with filtered water from Esbjerg Vest sewage treatment plant B1- COD/NVOC A1-BOD B1-BOD At the laboratory 1.00 ml of concentrate B1 is diluted up to ml with filtered water from Esbjerg Vest sewage treatment plant At the laboratory 6.00 ml of concentrate A1 is diluted up to ml with filtered water from Esbjerg Vest sewage treatment plant At the laboratory 6.00 ml of concentrate B1 is diluted up to ml with filtered water from Esbjerg Vest sewage treatment plant NVOC mg/l C a b a b BOD (w. ATU) mg/l O 2 c c TP mg/l P Cl mg/l SO 4 mg/l TSS mg/l A2 40.0g stock PO g stock Cl g stock SO 4 Sample B2 up to 40.0 kg (d+1.08) (e+22.2) (f+9.70) B g stock PO g stock Cl g stock SO 4 filtered water from Esbjerg Vest sewage treatment plant up to 70.0 kg A3 At the laboratory ml of filtered water from Esbjerg Vest sewage treatment plant is added to 4.5 ml stock TSS B3 At the laboratory ml of filtered water from Esbjerg Vest sewage treatment plant is added to 5.0 ml stock TSS d e f g g

21 ANNEX C CONTROL OF SPIKE VALUES COD Cr, mg/l O 2 Control of differences within sample pairs Laboratory Difference AB A B A - 25B UG 32-33A B UC No of labs., p 51 No of repl., n 2 d 0.62 s² 6.92 s 2.63 t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 15

22 BOD 5 w. ATU, mg/l O 2 Control of differences within sample pairs Laboratory Difference AB A - 22B A - 25B A B No of labs., p 17 No of repl., n 2 d s² s t = p (d/s) Sign. level, p(t) No test statistics were found to be significant 16

23 BOD 7 w. ATU, mg/l O 2 Control of differences within sample pairs Laboratory Difference AB A - 22B A - 25B A - 33B No of labs., p 13 No of repl., n 2 d s² s t = p (d/s) Sign. level, p(t) No test statistics were found to be significant 17

24 NVOC/TOC, mg/l C Control of differences within sample pairs Laboratory Difference AB UC A B A B UC A B UG UG No of labs., p 36 No of repl., n 2 d s² 0.13 s 0.37 t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 18

25 Total phosphorus, mg/l P Control of differences within sample pairs Laboratory Difference AB UC UC A B A B A B UC UC UC No of labs., p 64 No of repl., n 2 d s² s t = p (d/s) Sign. level, p(t) * * denotes that there is a significant difference (t-test, 5%-level) ** denotes that there is a significant difference (t-test, 1%-level) *** denotes that there is a significant difference (t-test, 0.1%-level) UC denotes a Cochran outlier Difference for sample pair AB is significantly different from 0, and data should be corrected with the difference (in spike value), during execution of Cochran's test. 19

26 Chloride, mg/l Control of differences within sample pairs Laboratory Difference AB UG 21-22A B A - 25B A - 33B UG UC No of labs., p 36 No of repl., n 2 d 0.2 s² 64.0 s 8.0 t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 20

27 Sulphate, mg/l Control of differences within sample pairs Laboratory Difference AB UC A B A - 25B A - 33B UG No of labs., p 19 No of repl., n 2 d s² 9.53 s 3.09 t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 21

28 Total suspended solids, mg/l Control of differences within sample pairs Laboratory Difference AB UG UC A - 22B A - 25B A B UG 72 - No of labs., p 50 No of repl., n 2 d 0.30 s² 4.24 s 2.06 t = p (d/s) Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 22

29 ANNEX D CONTROL OF RECOVERY COD Cr, mg/l O 2 Control of recovery, average of results Laboratory Sample pair AB A B A - 25B UG 32-33A B UC No of labs., p 51 No of repl., n 2 m s² s 4.95 Assigned value, µ 35 Recovery, % 97.8 t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 23

30 BOD 5 w. ATU, mg/l O 2 Control of recovery, average of results Laboratory Sample pair AB A - 22B A - 25B A B No of labs., p 17 No of repl., n 2 m s² s Assigned value, µ 4.1 Recovery, % t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant 24

31 BOD 7 w. ATU, mg/l O 2 Control of recovery, average of results Laboratory Sample pair AB A - 22B A - 25B A - 33B No of labs., p 13 No of repl., n 2 m s² s Assigned value, µ 4.8 Recovery, % 99.3 t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant 25

32 NVOC/TOC, mg/l C Control of recovery, average of results Laboratory Sample pair AB UC A B A B UC A B UG UG No of labs., p 36 No of repl., n 2 m s² 0.90 s 0.95 Assigned value, µ 14.0 Recovery, % t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 26

33 Total phosphorus, mg/l P Control of recovery, average of results Laboratory Sample pair AB UC UC A B A B A B UC UC UC No of labs., p 64 No of repl., n 2 m s² s Assigned value, µ 1.17 Recovery, % t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier 27

34 Chloride, mg/l Control of recovery, average of results Laboratory Sample pair AB UG 21-22A B A - 25B A - 33B UG UC No of labs., p 36 No of repl., n 2 m s² s 20.6 Assigned value, µ 451 Recovery, % t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 28

35 Sulphate, mg/l Control of recovery, average of results Laboratory Sample pair AB UC A B A - 25B A - 33B UG No of labs., p 19 No of repl., n 2 m s² s 4.74 Assigned value, µ 94 Recovery, % t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 29

36 Total suspended solids, mg/l Control of recovery, average of results Laboratory Sample pair AB UG UC A - 22B A B A B UG 72 - No of labs., p 50 No of repl., n 2 m s² 3.80 s 1.95 Assigned value, µ 64.4 Recovery, % 99.9 t = p (m-µ)/s Sign. level, p(t) No test statistics were found to be significant UC denotes a Cochran outlier UG denotes a Grubbs outlier 30

37 ANNEX E CONCENTRATION LEVEL Parameter Unit Sample Bottle no. I II Bottle Sample Assigned Spike Average Average value Measured Assigned COD mg/l O2 A1 23/73 33,10 33,10 33, , /20 33,40 33,40 47/7 33,10 33,10 B1 51/1 36,60 36,60 36, /28' 36,90 36,90 56/65 36,20 36,20 Total phosphorus mg/l P A2 38 1,34 1,34 1,33 1,31 0,14 0,14 1 1,33 1, ,33 1,33 B2 73 1,20 1,20 1,19 1,17 8 1,20 1, ,18 1,18 Chloride mg/l A ,00 464,00 453, ,00 33, ,00 453, ,00 444,00 B ,00 418,00 417, ,00 416, ,00 419,00 Sulphate mg/l A ,00 103,00 100, ,23 12, ,00 104, ,10 94,10 B ,90 90,90 89, ,60 85, ,90 90,90 Total suspended mg/l A3 66/14 67,00 67,00 66,33 64,4-7,00-7,40 solids 38/39 66,00 66,00 58/44 66,00 66,00 B3 32/7 72,00 72,00 73,33 71,8 8/65' 73,00 73,00 58/1 75,00 75,00 31

38 ANNEX F HOMOGENEITY AND STABILITY PT:SPIL-1 Parameter:NVOC Unit:mg/L C Sigma:0,9247 6,5% level Responsible for tests: IRL/mbf 6,5% level or 1,3*S T max Homogeneity test Date: Stability test Date: Sample x(a) x(b) average sd sd^2 Sample x(a) x(b) A ,5 14,3 14,4 0,148 0,022 A ,1 13,9 14,0 0,156 0,02 A ,1 14,1 14,1 0,028 0,001 A ,1 14,1 14,1 0,000 0,000 A ,2 14,1 14,2 0,092 0,008 A ,2 14,8 14,5 0,396 0,157 For stability A ,1 14,2 14,1 0,057 0,003 General average (y): A ,0 14,1 14,1 0,092 0,008 /x-y/ = A ,9 13,9 14,4 0,700 0,490 A ,8 13,9 13,9 0,085 0,007 A ,9 14,1 14,5 0,552 0,304 A ,4 14,6 14,5 0,141 0,020 Conclusions ss = 0, *sigma=0,28 For homogeneity /x-y/ = General average (x) 14,23 Analytical Is s w < 0,15*sigma Sample average sd (s x) 0,214 quality NO Within-sample sd (s w): 0,295 Between-samples sd (ss): 0,0470 Homogeneity: Is ss < 0.3*sigma? S L in the Proficiency Test: YES S R in the Proficiency Test: Stability: /x-y/ < 0.3*sigma? No data 32

39 PT: SPIL-1 Parameter: TP Unit: mg/l P Sigma: 0,0874 6,5% level Responsible for tests: IRL/mbf 6,5% level or 1,3*S T max Homogeneity test Date: Stability test Date: IRL Sample x(a) x(b) average sd sd^2 Sample x(a) x(b) A2-44 1,3 1,4 1,4 0,049 0,002 A2-38 1,34 A2-9 1,3 1,4 1,4 0,057 0,00 A2-1 1,33 A2-69 1,4 1,3 1,4 0,035 0,001 A2-95 1,33 A2-84 1,3 1,3 1,3 0,000 0,000 A2-24 1,3 1,4 1,3 0,021 0,000 A ,4 1,4 1,4 0,007 0,000 For stability A2-99 1,3 1,3 1,3 0,035 0,001 General average (y): 1, A2-40 1,3 1,4 1,3 0,014 0,000 /x-y/ = 0,01125 A2-53 1,4 1,4 1,4 0,007 0,000 A2-69 1,3 1,3 1,3 0,000 0,000 A2-82 1,3 1,3 1,3 0,021 0,000 A2-19 1,4 1,3 1,3 0,014 0,000 Conclusions ss = 0, *sigma= 0,03 For homogeneity /x-y/ = 0,01125 General average (x) 1,34 Analytical Is s w < 0,15*sigma Sample average sd (s x) 0,018 quality NO Within-sample sd (s w): 0,028 Between-samples sd (ss): 0 Homogeneity: Is ss < 0.3*sigma? S L in the Proficiency Test: YES S R in the Proficiency Test: Stability: /x-y/ < 0.3*sigma? YES 33

40 PT: SPIL-1 Parameter: TSS Unit: mg/l Sigma: 4,8 6,5% level Responsible for tests: IRL/mbf 6,5% level or 1,3*S T max Homogeneity test Date: Stability test Date: IRL Sample x(a) x(b) average sd sd^2 Sample x(a) x(b) B ,3 73,3 B B ,5 73,5 B B ,35 B B ,4 73,4 B ,3 74,3 B ,6 73,6 For stability B ,6 73,6 General average (y): 73, B ,9 73,9 /x-y/ = 0, B ,7 71,7 B ,6 73,6 B ,9 71,9 B ,7 73,7 Conclusions For homogeneity /x-y/ = 0, ss = 0,79 0.3*sigma= 1,43 General average (x) 73,3 Analytical Is s w < 0,15*sigma Sample average sd (s x) 0,792 quality No data Within-sample sd (s w): Between-samples sd (ss): 0,792 Homogeneity: Is ss < 0.3*sigma? S L in the Proficiency Test: S R in the Proficiency Test: A hole was made in the filter c during preparation B Stability: YES /x-y/ < 0.3*sigma? YES 34