CHEK Proficiency study 672 Phthalates in nail polish Date 5 December 2017 Version 1 Status Final Report number CHEK-17-672 page 0
Colophon Number 672 Name Phthalates in nail polish Contact Author Authorization Netherlands Food and Consumer Product Safety Authority (NVWA) CHEK working group Paterswoldseweg 1 9726 BA Groningen The Netherlands PO Box 43006 3540 AA Utrecht The Netherlands T +31 088 223 33 33 chek@vwa.nl www.nvwa.nl/chek ISBN 1380-51 Mariëlle van Vondel Krista Bouma (operational manager) page 1
Content 1 Introduction 1 2 Time-table 1 3 Sample preparation 1 4 Statistical results 2 4.1 DEHP in nail polish samples uniform level 3 4.2 DBP in nail polish samples uniform level 4 4.3 BBP in nail polish samples uniform level 5 4.4 Summary phthalates in nail polish 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 9-17 page 0
1 Introduction Proficiency study 672 as directed by the CHEK working group concerned the investigation of the di(2-ethylhexyl) phthtalate (DEHP), dibutyl phthalate (DBP) and benzylbutyl phthalate (BBP), contents of two nail polish samples. To get an impression of the performance of the quantitative determination of DEHP, DBP and BBP in nail polish 10 laboratories were invited to join this proficiency study. 2 Time-table Homogeneity of samples 12 September 2017 Distribution of samples 30 October 2017 Deadline for the production of results 1 December 2017 Final report 5 December 2017 3 Sample preparation Nail polish samples A and B uniform level 0.28 gram DEHP (CAS 117-81-7), 0.50 gram DBP (CAS 84-74-2) and 0.30 gram BBP (CAS 85-68-7) were added to 411 gram nail polish, yielding near 0.0688% m/m DEHP, 0.123% m/m DBP and 0.0737% m/m BBP for each phthalate. The sample was minced by hand for a few minutes. After homogenisation sub-samples of about 5 g were prepared in dark glass vials. Homogeneity 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 DEHP, DBP and BBP contents (see table III). The average contents were 0.0989% m/m DEHP, 0.122% m/m DBP and 0.104% m/m BBP. Stability The stability was not checked yet. The samples are expected to be stable during the period of this study. Instructions 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 (+20 C) and to mix each sample before analyses. page 1
4 Statistical results The results of the laboratories and the Z-scores are given in table I and II. 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. Target standard deviation For the target standard deviation in most of the cases Horwitz shows a good maximum allowable (or acceptable) RSD R but does not include different levels of complexity of analytical methods. If the target standard deviation is not chosen realistically the interpretation satisfactory, questionable and unsatisfactory is not that reliable. Therefore in this proficiency study precision data of the past five proficiency studies on DEHP, DBP and BBP in PVC were used to set a target reproducibility standard deviation (s R ). These components are similar. The acceptable RSD R for DEHP, DBP and BBP is set at 17%. Therefore this value was used as target standard deviation to calculate the Z-scores and the performances. Performance The performance of a determination is assessed as following: satisfactory = maximum allowable RSD R 2 questionable = 2< maximum allowable RSD R <3 unsatisfactory = maximum allowable RSD R 3 page 2
4.1 DEHP in nail polish uniform level 4.1.1 DEHP in nail polish samples A and B uniform level 10 labs: Results of all laboratories 10 labs Unit Average 0.0716 % m/m Repeatability standard deviation (s r ') 0.0038 % m/m Repeatability rel. standard deviation (RSD r ') 5.3 % Reproducibility standard deviation (s R ') 0.023 % m/m Reproducibility rel. standard deviation (RSD R ') 32 % Acceptable value for (RSD R ') 17 % Repeatability r' 0.011 % m/m Reproducibility R' 0.064 % m/m 4.1.2 Summary DEHP in nail polish uniform level The results of this and earlier proficiency studies are summarised in the table below. Prof. study Number of labs Average % m/m RSD R % Acceptable RSD R % 672 10 0.0716 32 17 652 12 0.0353 16 17 628 16 0.0567 21 17 4.1.3 Conclusions DEHP in nail polish samples A and B uniform level The performance of the determination of nail polish in nail polish is satisfactory. There is not a direct relationship between the method of analysis (i.e. extraction, technique or detector) and the results (i.e. Z-score), see table II. The results approach a normal distribution. No Cochran or Grubbs outliers are found in the datasets of sample A and B. The absolute Z-score of laboratory 6 is greater than 3 and suggests poor performance in terms of accuracy. page 3
4.2 DBP in nail polish uniform level 4.2.1 DBP in nail polish samples A and B uniform level 10 labs: Results of all laboratories 10 labs Unit Average 0.107 % m/m Repeatability standard deviation (s r ') 0.0068 % m/m Repeatability rel. standard deviation (RSD r ') 6.3 % Reproducibility standard deviation (s R ') 0.034 % m/m Reproducibility rel. standard deviation (RSD R ') 31 % Acceptable value for (RSD R ') 17 % Repeatability r' 0.019 % m/m Reproducibility R' 0.094 % m/m 4.2.2 Summary DBP in nail polish uniform level The results of this and earlier proficiency studies are summarised in the table below. Prof. study Number of labs Average % m/m RSD R % Acceptable RSD R % 672 10 0.107 31 17 652 14 0.0404 22 17 628 13 0.0623 11 17 4.2.3 Conclusions DBP in nail polish samples A and B uniform level The performance of the determination of DBP in nail polish is satisfactory. There is not a direct relationship between the method of analysis (i.e. extraction, technique or detector) and the results (i.e. Z-score), see table II. 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 1 are marked as stragglers by the Cochran test indicating bad repeatability but are not rejected. The absolute Z-scores of laboratories 2 and 6 are greater than 3 and suggest poor performance in terms of accuracy. page 4
4.3 BBP in nail polish uniform level 4.3.1 BBP in nail polish samples A and B uniform level 10 labs: Results of all laboratories 10 labs Unit Average 0.0782 % m/m Repeatability standard deviation (s r ') 0.0042 % m/m Repeatability rel. standard deviation (RSD r ') 5.4 % Reproducibility standard deviation (s R ') 0.027 % m/m Reproducibility rel. standard deviation (RSD R ') 35 % Acceptable value for (RSD R ') 17 % Repeatability r' 0.012 % m/m Reproducibility R' 0.076 % m/m 4.3.2 Summary BBP in nail polish uniform level The results of this and earlier proficiency studies are summarised in the table below. Prof. study Number of labs Average % m/m RSD R % Acceptable RSD R % 672 10 0.0782 35 17 652 14 0.0372 32 17 628 14 0.0632 13 17 4.3.3 Conclusions BBP in nail polish samples A and B uniform level The performance of the determination of DBP in nail polish is questionable, this is cause by the large spread in results. There is not a direct relationship between the method of analysis (i.e. extraction, technique or detector) and the results (i.e. Z-score), see table II. 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 1 are marked as stragglers by the Cochran test indicating bad repeatability but are not rejected. The results of laboratories 1 and 6 are (also) marked as stragglers by the Grubbs test indicating systematic errors but are not rejected. The absolute Z-scores of laboratories 1, 2 and 6 are greater than 3 and suggest poor performance in terms of accuracy. page 5
4.4 Summary phthalates in nail polish The results of this proficiency study are summarised in the table below. Number of accepted results Average [% m/m] RSD R [%] DEHP 10 0.0716 32 DBP 10 0.107 31 BBP 10 0.0782 35 5 Method of analysis Lab Extraction* Technique Detector Samples/ year 1 EA GC MS 300 2 THF/H GC MS 1500-2000 3 THF/H GC FID - 4 ACE GC MS 20 5 AE/ACE GC MS 100 6 CH GC MS 218 7 EA/CH GC MS 150 8 THF/H GC MS 500 9 MTBE GC MS 600 10 - GC MS - * Abbreviation extraction solvents: ACE = acetone CH = cyclohexane EA = ethylacetate H = hexane MTBE = methyl-tert-butylether THF = tetrahydrofuran page 6
6 Remarks from participants The participants made no remarks. 7 List of invited participants Europe France - 1 participant Germany - 5 participants Hungary - 1 participant Spain- 1 participant The Netherlands - 1 participant Outside Europe Taiwan - 1 participant page 7
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 Where: x = an (average) laboratory result = the average result of all laboratories (calculated exclusive outliers). = an assigned precision standard (17% of average) calculated stated after five similar proficiency studies DEHP, DBP and BBP in PVC As a fixed target value the maximum allowable standard deviation is used calculated from the past five proficiency studies. 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 and the 2sand 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
9 Tables and graphical presentations Table I; Proficiency study 672: DEHP, DBP and BBP in nail polish [% m/m] Lab DEHP DBP BBP A B Z-score A B Z-score A B Z-score 1 0.0474 0.0344-2.52 0.0778 0.0530-2.30 0.0433 0.0282-3.19 2 0.087 0.088 1.31 0.164 0.166 3.16 0.119 0.117 3.00 3 0.087 0.087 1.26 0.123 0.121 0.80 0.087 0.086 0.63 4 0.0803 0.0807 0.73 0.117 0.116 0.50 0.103 0.100 1.76 5 0.0740 0.0720 0.11 0.120 0.118 0.64 0.0720 0.0750-0.35 6 0.0279 0.0191-3.95 0.0492 0.0399-3.44 0.0338 0.0283-3.55 7 0.0763 0.0776 0.44 0.106 0.106-0.07 0.0909 0.0949 1.11 8 0.1001 0.0941 2.09 0.1351 0.1211 1.14 0.0808 0.0884 0.48 9 0.0691 0.0694-0.19 0.101 0.1012-0.34 0.0765 0.0773-0.10 10 0.081 0.0797 0.72 0.106 0.105-0.10 0.0808 0.0811 0.21 0.0716 0.107 0.0782 σ 0.012 0.018 0.013 (1) = Cochran outlier (2) = Grubbs outlier (3)= Results removed by hand page 9
Table II; Relation Z-scores and method of analysis Lab DEHP DBP BBP Method 2 1.31 3.16 3.00 THF/H-GC-MS 8 2.09 1.14 0.48 3 1.26 0.80 0.63 THF/H-GC-FID 1-2.52-2.30-3.19 EA-GC-MS 5 0.11 0.64-0.35 AE/ACE-GC-MS 7 0.44-0.07 1.11 EA/CH-GC-MS 4 0.73 0.50 1.76 ACE-GC-MS 6-3.95-3.44-3.55 CH-GC-MS 9-0.19-0.34-0.10 MTBE-GC-MS 10 0.72-0.10 0.21?-GC-MS Method: Extraction Technique Detector ACE = acetone GC MS CH = cyclohexane EA = ethylacetate H = hexane MTBE = methyl-tert-butylether THF = tetrahydrofuran FID page 10
Table III; Homogeneity of samples for DEHP, DBP and BBP in nail polish [% m/m] Sample no 1st analysis DEHP DBP BBP 2nd analysis 1st analysis 2nd analysis 1st analysis 2nd analysis 1 0.110 0.0948 0.122 0.118 0.110 0.101 2 0.0956 0.101 0.121 0.123 0.102 0.106 3 0.0920 0.0970 0.126 0.121 0.101 0.103 4 0.0948 0.0994 0.118 0.122 0.102 0.104 5 0.0964 0.0990 0.133 0.123 0.104 0.105 6 0.0955 0.0964 0.118 0.121 0.101 0.103 7 0.0989 0.100 0.120 0.119 0.104 0.107 8 0.100 0.0993 0.122 0.124 0.104 0.102 9 0.0983 0.105 0.120 0.118 0.105 0.108 10 0.0958 0.109 0.131 0.121 0.101 0.115 average 0.0977 0.100 0.123 0.121 0.104 0.105 t-test t samples -1.05 1.34-0.97 t critical,95% 2.26 2.26 2.26 Homogeneity S between 0 0.00154 0 S within 0.00511 0.00364 0.00401 0.00560 0.00670 0.00587 S between / 0 0.230 0 Based on the t-test there is no significant difference between the averages of 1st and the 2nd analysis for DEHP, DBP and BBP. The ratio of the sampling standard deviation and the target value for DEHP, DBP and BBP is lower than the recommended value of 0.3. Samples are regarded as sufficient homogeneous for the purpose of the proficiency study. S between S within σ = between samples standard deviation = within samples standard deviation = target value (17% of average) calculated after five similar proficiency studies DEHP, DBP and BBP in PVC page 11
Graphical presentations DEHP in nail polish Figure Ia; Saw-tooth plot DEHP in nail polish, calculated with target s. Figure Ib; Saw-tooth plot DEHP in nail polish, calculated with group s. page 12
Figure II; Youden plot DEHP in nail polish. Figure III; Z-score DEHP in polish. page 13
Graphical presentations DBP in nail polish Figure IVa; Saw-tooth plot DBP in nail polish, calculated with target s. Figure IVb; Saw-tooth plot DBP in nail polish, calculated with group s. page 14
Figure V; Youden plot DBP in nail polish. Figure VI; Z-score DBP in nail polish. page 15
Graphical presentations BBP in nail polish Figure VIIa; Saw-tooth plot BBP in nail polish, calculated with target s. Figure VIIb; Saw-tooth plot BBP in nail polish, calculated with group s. page 16
Figure VIII; Youden plot BBP in nail polish. Figure IX; Z-score BBP in nail polish page 17