CHEK Proficiency study 644. Solvents in adhesive. Date 15 October 2016 Version 1 Status Final Report number CHEK

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1 CHEK Proficiency study 644 Solvents in adhesive Date 15 October 2016 Version 1 Status Final Report number CHEK page 0

2 Colophon Number 644 Name Solvents in adhesive Contact Author Netherlands Food and Consumer Product Safety Authority (NVWA) CHEK working group Paterswoldseweg BA Groningen The Netherlands PO Box AA Utrecht The Netherlands T chek@vwa.nl ISBN Mariëlle van Vondel Authorization Krista Bouma (operational manager) page 1

3 Content 1 Introduction 1 2 Time-table 1 3 Sample preparation 1 4 Statistical results Benzene in adhesive samples uniform level Toluene in adhesive samples uniform level Chloroform in adhesive samples uniform level Summary solvents in adhesive 6 5 Methods of analysis 6 6 Remarks from participants 7 7 List of invited participants 7 8 Explanation of graphical presentations 8 9 Tables and graphical presentations 9-16 page 0

4 1 Introduction Proficiency study 644 as directed by the CHEK working group concerned the investigation of solvents benzene (CAS no ), toluene (CAS no ) and chloroform (CAS no ) contents of two adhesive samples. To get an impression of the performance of the quantitative determination of solvents in adhesive 19 laboratories were invited to join this proficiency study. 2 Time-table Homogeneity of samples 18 July 2016 Distribution of samples 29 August 2016 Deadline for the production of results 30 September 2016 Final report 15 October Sample preparation Adhesive samples A and B uniform level 587 g adhesive (solution of rubber in a mixture of solvents) was obtained from the local market g benzene (CAS no ), 1.75 g toluene (CAS no ) and 1.75 g chloroform (CAS no ) were added to the adhesive and thoroughly minced in a plastic container by shaking for 1 hour in a powder blender. After homogenisation approximately 80 sub-samples of about 5 g were prepared in plastic sachets. The homogeneity was checked by the laboratory of the Netherlands Food and Consumer Product Safety Authority, Groningen by randomly selected samples for the determination of the benzene (CAS no ), toluene (CAS no ) and chloroform (CAS no ) contents (see table II). The average contents were 0.274% m/m benzene, 0.267% m/m toluene and 0.314% m/m chloroform. Samples were stored at room temperature (+20 C) in the dark until shipment. To each of the participants two samples coded A and B were sent. Participants were instructed to store the samples at room temperature in a dark place and to mix each samples before analyses. page 1

5 4 Statistical results Results and Z -scores The results of the laboratories and the Z -scores are given in table I. Figures I to IX give graphical presentations of the results. One-way analysis of variance (ANOVA), preceded by checking for normality and outlier checking of the results (Cochran/Grubbs) is the statistical procedure for obtaining the estimates of withinlaboratory and between laboratory variability. Standard uncertainty In this proficiency study the standard uncertainty u x was higher than 0.3 times the assigned standard deviation according to Horwitz. According to ISO 13528:2005 this means that the uncertainty is not longer negligible and needs to be included in the interpretation of the results of the proficiency study. So in this proficiency studies Z - scores are calculated (instead of the usual Z-scores), which include the standard uncertainty. A standard uncertainty (u x ) was calculated according to ISO 13528:2005 as following: u x = 1.25 s n Where: s = standard deviation of results of laboratories (calculated exclusive outliers). n = number of laboratories (calculated exclusive outliers). Performance The performance of a determination is assessed as following: satisfactory = 0-2 x maximum allowable RSD R (including uncertainty) questionable = >2-3 x maximum allowable RSD R (including uncertainty) unsatisfactory = >3 x maximum allowable RSD R (including uncertainty) For the target standard deviation in most of the cases Horwitz shows a good maximum allowable RSD R but does not include different levels of complexity of analytical method. If the target standard deviation is not chosen realistically the interpretation satisfactory, questionable and unsatisfactory is not valid. In this study it is more adequate to use the reproducibility standard deviation (s R ) as target standard deviation and maximum allowable RSD R. So this proficiency study provides precision data for these specific analyses. page 2

6 4.1 Benzene in adhesive uniform level Benzene in adhesive samples A and B 18 labs : Results of all laboratories 16 labs : Results of laboratories 6 and 13 are rejected by the Cochran test 18 labs 16 labs Unit Average % m/m Repeatability standard deviation (s r ') % m/m Repeatability rel. standard deviation (RSD r ') % Reproducibility standard deviation (s R ') % m/m Reproducibility rel. standard deviation (RSD R ') % Horwitz acceptable value for (RSDR') % Horwitz acceptable value for (RSDR'), including u x % Repeatability r' % m/m Reproducibility R' % m/m Summary benzene in adhesive samples A and B The results of this and earlier performed proficiency studies are summarised in the table below. Prof. study Number of labs Average % m/m RSD R % Acceptable RSD R % Conclusions benzene in adhesive samples A and B The performance of the determination of benzene in adhesive is questionable, this is caused by the large spread in results. The results approach a normal distribution. The results of laboratories 6 and 13 are marked as outliers by the Cochran test indicating bad repeatability and are rejected. The results of laboratory 3 are marked as stragglers by the Cochran test indicating bad repeatability but are not rejected. No Grubbs outliers are found in the datasets of sample A and B. The results of laboratories 11 and 19 are marked as stragglers by the Grubbs test indicating systematic errors but are not rejected. The absolute Z -scores of laboratories 3, 11, 13, 15 and 19 are greater than 3 and suggest poor performance in terms of accuracy. page 3

7 4.2 Toluene in adhesive uniform level Toluene in adhesive samples A and B 19 labs : Results of all laboratories 19 labs Unit Average % m/m Repeatability standard deviation (s r ) % m/m Repeatability rel. standard deviation (RSD r ) 4.2 % Reproducibility standard deviation (s R ) 0.13 % m/m Reproducibility rel. standard deviation (RSD R ) 44 % Horwitz acceptable value for (RSDR ) 4.8 % Horwitz acceptable value for (RSDR ), including u x 13 % Repeatability r % m/m Reproducibility R 0.37 % m/m Summary toluene in adhesive samples A and B The results of this and earlier performed proficiency studies are summarised in the table below. Prof. study Number of labs Average % m/m RSD R % Acceptable RSD R % Conclusions toluene in adhesive samples A and B The performance of the determination of toluene in adhesive is unsatisfactory, this is caused by the large spread in results. The results approach a normal distribution. No Cochran or Grubbs outliers are found in the datasets of sample A and B. The results of laboratory 13 are marked as stragglers by the Cochran test indicating bad repeatability but are not rejected. The absolute Z -scores of laboratories 1, 3, 7, 11, 13, 15 and 19 are greater than 3 and suggest poor performance in terms of accuracy. page 4

8 4.3 Chloroform in adhesive uniform level Chloroform in adhesive samples A and B 14 labs : Results of all laboratories 13 labs : Results of laboratory 13 are rejected by the Cochran test 14 labs 13 labs Unit Average % m/m Repeatability standard deviation (s r ') % m/m Repeatability rel. standard deviation (RSD r ') % Reproducibility standard deviation (s R ') % m/m Reproducibility rel. standard deviation (RSD R ') % Horwitz acceptable value for (RSDR') % Horwitz acceptable value for (RSDR'), including u x % Repeatability r' % m/m Reproducibility R' % m/m Summary chloroform in adhesive samples A and B The results of this and an earlier performed proficiency study are summarised in the table below. Prof. study Number of labs Average % m/m RSD R % Acceptable RSD R % Conclusions chloroform in adhesive samples A and B The performance of the determination of chloroform in adhesive is questionable, this is caused by the large spread in results. The results approach a normal distribution. The results of laboratory 13 are marked as outliers by the Cochran test indicating bad repeatability and are rejected. No Grubbs outliers are found in the datasets of sample A and B. The absolute Z -scores of laboratories 1, 3 and 11 are greater than 3 and suggest poor performance in terms of accuracy. page 5

9 4.4 Summary solvents in adhesive The results of this proficiency study are summarised in the table below. Number of accepted results Average [% m/m] Benzene Toluene Chloroform RSD R [%] 5 Method of analysis Lab GC MS FID Extraction solvent Samples/year 1 x - 2 x x - 3 x x x MTBE - 5 x x ACE - 6 x x THF - 8 x x DMF - 9 x x DMI x x DCM x x ACE x x ACE x x - 14 x x x x MeOH - 16 x x ACE/THF 10 (for benzene and chloroform) x x H (for toluene) 17 x x - 18 x x MTBE x x 500 ACE = acetone DCM = dichloromethane DMF = dimethylformamide MeOH = methanol MTBE = methyl-tert-butyl ether H = hexane THF = tetrahydrofuran page 6

10 6 Remarks from participants Lab 7 Used method is accordance with Japan Food Sanitation Law 370. Lab 10 Benzene was overlaid by cyclohexane and chloroform was overlaid by methylcyclopentane. Lab 14 The method of analysis reports the results to two significant figures (ex. 0.34% m/m). 7 List of invited participants Europe France - 1 participant Germany - 5 participants Italy - 1 participant The Netherlands - 2 participants Spain 1 participant Outside Europe Brazil 1 participant China - 3 participants Cyprus 1 participant Hong Kong - 2 participants Taiwan 1 participant Thailand 1 participants page 7

11 8 Explanation of graphical presentations Z -score As a criterion for evaluation of the performance of an individual laboratory a socalled Z -score is used. The Z -score is given by the following equation: Z' = x µ u 2 x + σ 2 Where: x = an (average) laboratory result µ = the average result of all laboratories (calculated exclusive outliers). σ = an assigned precision standard (according to Horwitz). = uncertainty of this proficiency study. u x As a fixed target value the maximum allowable standard deviation is used calculated according to Horwitz. The Z -score for an individual laboratory can be compared with those of previous proficiency studies to determine whether the laboratory performance has improved. Because Z is standardised, it is comparable for all analytes, testmaterials and analytical methods. In general, an absolute value of Z greater than three suggests poor performance in terms of accuracy. When overall performance in a specific interlaboratory test is graded as good, values of Z <1 would be very common and values of Z >3 would be very rare. It is possible to classify these scores: Satisfactory = Z 2 Questionable = 2 < Z < 3 Unsatisfactory = Z 3 Saw-tooth plot The results of the samples are presented in a so-called saw-tooth plot. In this figure individual results of two (nearly) identical individual results are plotted. The average of the sample, the 2s- and 3s-intervals of the target values (Horwitz plus uncertainty) and the 2s- and 3s-intervals after removal of outliers are also included (group s). Youden-plot Based on Youden statistics the calculated variance is split in a variance caused by systematic and random errors of the individual laboratories. It is necessary that the samples are similar. Generally the points form an elliptical pattern with the major axis of the ellipse running diagonally at an angle of 45 to the X-axis. The lengths of the perpendiculars drawn from the points to the 45 line are directly related to the random errors. Systematic errors will be presented along the 45 line. The perpendiculars intersect the 45 line at various distances from the point through which the 45 line was drawn. These distances are directly related to the systematic errors. page 8

12 9 Tables and graphical presentations Table I; Proficiency study 644: benzene, toluene and chloroform in adhesive [% m/m] Lab Benzene Toluene Chloroform Method* Sample A Sample B Z -score Sample A Sample B Z -score Sample A Sample B Z -score GC GC-MS GC MTBE-GC-MS ACE-GC-MS (1) (1) GC-MS THF DMF-GC-FID DMI-GC-MS DCM-GC-MS ACE-GC-MS ACE-GC-MS (1) (1) (1) (1) GC-MS GC-MS MeOH-GC-MS H/ACE+THF-GC-MS/FID GC-MS MTBE-GC-MS GC-MS µ σ u x (1) = Cochran outlier (2) = Grubbs outlier (3) = Results removed by hand page 9

13 Table II; Homogeneity of samples for solvents in adhesive [% m/m] Sample no 1st analysis Benzene Toluene Chloroform 2nd analysis 1st analysis 2nd analysis 1st analysis 2nd analysis average t-test t samples t critical,95% Homogeneity S between S within σ S between /σ Based on the t-test there is no significant difference between the averages of 1st and the 2nd analysis of all solvents. The ratio of the sampling standard deviation and the target value σ for all solvents is lower than the recommended value of 0.3. Samples are regarded as sufficient homogeneous for the purpose of the proficiency study. S between = between samples standard deviation S within = within samples standard deviation σ = target value calculated from the Horwitz equation or assigned precision standard. page 10

14 Graphical presentations benzene in adhesive Figure Ia; Saw-tooth plot benzene in adhesive, calculated with target s. Figure Ib; Saw-tooth plot benzene in adhesive, calculated with group s (exclusive laboratories 6 and 13). page 11

15 Figure II; Youden plot benzene in adhesive. Figure III; Z -score benzene in adhesive. page 12

16 Graphical presentations toluene in adhesive Figure IVa; Saw-tooth plot toluene in adhesive, calculated with target s. Figure IVb; Saw-tooth plot toluene in adhesive, calculated with group s. page 13

17 Figure V; Youden plot toluene in adhesive. Figure VI; Z -score toluene in adhesive. page 14

18 Graphical presentations chloroform in adhesive Figure VIIa; Saw-tooth plot chloroform in adhesive, calculated with target s. Figure VIIb; Saw-tooth plot chloroform in adhesive, calculated with group s (exclusive laboratory 13). page 15

19 Figure VIII; Youden plot chloroform in adhesive. Figure IX; Z -score chloroform in adhesive. page 16