Results of Proficiency Test Isopropanol (Isopropyl alcohol) November 2006

Transcription

1 Results of Proficiency Test Isopropanol (Isopropyl alcohol) November 26 Organised by: Authors: Correctors: Report: Institute for Interlaboratory Studies Spijkenisse, the Netherlands Ing. W. Leung Dr. R.G. Visser & ing. S. Lagendijk iis6c15 X February 27

2 CONTENTS 1 INTRODUCTION SET UP QUALITY SYSTEM PROTOCOL SAMPLES STABILITY OF THE SAMPLES ANALYSES RESULTS STATISTICS GRAPHICS Z-SCORES EVALUATION EVALUATION PER TEST PERFORMANCE EVALUATION FOR THE GROUP OF LABORATORIES COMPARISON OF THE PT OF NOVEMBER 26 WITH THE PREVIOUS PT... 9 Appendices: 1. Data and statistical results Gaschromatographic conditions List of participants Abbreviations and literature Isopropanol: iis6c15 - X page 2 of 29

3 1 INTRODUCTION On request of several participants, it was decided to organise again a round robin for the analysis of Isopropanol (Isopropyl alcohol) during the annual proficiency test program of 26/27. The proficiency test of Isopropanol has been organised in accordance with the latest applicable version of the ASTM D77:5 specification and few additional tests requested by the participants. In this international interlaboratory study 15 laboratories out of 11 different countries have participated. See appendix 3 for a list of participants in alphabetical country order. In this report the results of the proficiency test are presented and discussed. 2 SET UP The Institute for Interlaboratory studies (i.i.s.) in Spijkenisse, The Netherlands, was the organiser of this proficiency test. It was decided to send 1 sample (1*5 ml, labelled 688). Participants were requested to report rounded and unrounded results. The unrounded results were preferably used for statistical evaluations. 2.1 QUALITY SYSTEM The Institute for Interlaboratory Studies in Spijkenisse, the Netherlands, has implemented a quality system based on ISO guide 43 and ILAC-G13:2. This ensures 1% confidentiality of participant s data. Also customer s satisfaction is measured on a regular basis by sending out questionnaires. 2.2 PROTOCOL The protocol followed in the organisation of this proficiency test was the one as described for proficiency testing in the report i.i.s. Interlaboratory Studies: Protocol for the Organisation, Statistics and Evaluation of November 23 (i.i.s.-protocol, version 3.). 2.3 SAMPLES The necessary bulk material was purchased from a local trader. The approximately 25 litre bulk sample was homogenised in a pre-cleaned can. After homogenisation, 2 subsamples were transferred to 5 ml brown glass bottles, labelled 688. The homogeneity of subsample 688 was checked by determination Density in accordance with ASTM D 452:2e1 and Water in accordance with ASTM D 1364:2 on 4 stratified random selected samples. Isopropanol: iis6c15 - X page 3 of 29

4 Density at 2ºC in kg/l Water content in mg/kg sample sample sample sample Table 1: homogeneity test of subsample 688 From the results in table 1, the repeatability of the results was calculated by multiplication of the standard deviations by 2.8: Density at 2ºC in kg/l Water in mg/kg r (sample 688) reference test ASTM D 452:2e1 ASTM D 1364:2 r (reference test) Table 2: repeatabilities of subsamples 688 The repeatabilities of the density and water for sample 688 were in agreement with the respective methods. Therefore homogeneity of the subsamples was assumed. One sample of Isopropanol (5 ml of sample 688) was sent to the participating laboratories on November 22, STABILITY OF THE SAMPLES In order to be sure that the material, which was used in this proficiency test, was stable for the valid period, the stability of the material, packed in the brown glass bottles, was checked prior to use. 2.5 ANALYSES The participants were asked to determine Acidity, Anorganic Chloride, Appearance, Apparent Density 2ºC, Colour Pt/Co, 2ºC, Distillation (IBP & DP), Nonvolatile Matter, Water, Purity (on dry basis), Ethanol, n-propanol, n-butanol, Methyl-Ethyl-Ketone and Other Impurities on sample 688. To get comparable results, a detailed report form on which the units and the standard methods were printed was sent together with the sample. Also a letter of instructions and a MSDS were added to the package. 3 RESULTS During four weeks after sample despatch the results of the individual laboratories were gathered. The original data are tabulated per determination in appendix 1 of this report. The laboratories are presented by their code numbers. Directly after the deadline, a reminder fax was sent to the laboratories that had not reported results at that moment. Shortly after the deadline the available results were Isopropanol: iis6c15 - X page 4 of 29

5 screened for suspect data. A result was called suspect in case the Huber Elimination Rule (a robust outlier test) found it to be an outlier. The laboratories that produced these suspect data were asked to check the results. Additional or corrected results are used for data analysis and original results are placed under 'Remarks' in the result tables in appendix STATISTICS For the statistical evaluation the unrounded (when available) figures were used instead of the rounded results. Results reported as '< ' or '> ' were not used in the statistical evaluation. First the normality of the distribution of the various data sets per determination was checked by means of the Lilliefors-test. After removal of outliers this check was repeated. Not all data sets proved to have a normal distribution, in which cases the statistical evaluation of the results should be used with due care. In accordance to ISO 5725 (1986 and 1994) the original results per determination were submitted subsequently to Dixon and Grubbs outlier tests. Outliers are marked by D(.1) for the Dixon test, by G(.1) or DG(.1) for the Grubbs test. Stragglers are marked by D(.5) for the Dixon test, by G(.5) or DG(.5) for the Grubbs test. Both outliers and stragglers were not included in the calculations of averages and standard deviations. Finally the reproducibilities were calculated from the standard deviations by multiplying them with a factor of 2.8. Statistical calculations were performed as described in the report i.i.s. Interlaboratory Studies: Protocol for the Organisation, Statistics and Evaluation of November 23 (i.i.s.- protocol, version 3.). 3.2 GRAPHICS In order to visualise the data against the reproducibilities from literature, Gauss plots were made, using the sorted data for one determination (see appendix 1). On the Y-axis the results are plotted. The corresponding laboratory numbers are under the X-axis. A straight line presents the average of the reported data. Two striped lines present the reproducibility limits of the selected standard, calculated as mean ± target reproducibility, parallel to the average line. Outliers and other data, which were excluded from the calculations, are represented as a cross. Accepted data are represented as a triangle. Furthermore, Kernel Density Graphs were made. This is a method for producing a smooth density approximation to a set of data that avoids some problems associated with histograms (see appendix 4; nr.12 and 13) 3.3 Z-SCORES To evaluate the performance of the participating laboratories the z-scores were calculated. As it was decided to evaluate the performance of the participants in this proficiency test (PT) against the literature requirements, e.g. ASTM reproducibilities, the z- scores were calculated using a target standard deviation. This results in an evaluation independent of the spread of this interlaboratory study. Isopropanol: iis6c15 - X page 5 of 29

6 The target standard deviation was calculated from the literature reproducibility by division with 2.8. The z-scores were calculated in accordance with: z (target) = (result - average of PT) / target standard deviation Absolute values for z<2 are very common and absolute values for z>3 are very rare. The usual interpretation of z-scores is as follows: z < 1 good 1 < z < 2 satisfactory 2 < z < 3 questionable 3 < z unsatisfactory 4 EVALUATION In this proficiency test no problems were encountered with despatch of the samples. From the total of 15 participants, three participants did send in their results after the deadline for reporting and one participant didn t report any results at all. Finally, 14 reporting laboratories did send in 139 numerical results. Observed were 9 outlying results, which is 6.5 %. In proficiency studies outlier percentages of 3 % % are quite normal. 4.1 EVALUATION PER TEST In this section the results are discussed per test. When no literature reproducibility was available, other target values were used. In those cases the Horwitz equation is used to estimate the target reproducibility. Not normal distributions were found for the following determinations: Chloride as Cl, Colour Pt/Co, 2 C, Distillation (IBP), Water, n-propanol and Methyl-Ehtyl- Ketone. In these cases the statistical evaluation should be used with due care. Acidity: No analytical problems were observed. No results were outside the reproducibility limits and the observed reproducibility is in good agreement with the requirements of ASTM D 1613:6. Anorg. Chloride: This determination is not problematic. No results were outside the reproducibility limits and the observed reproducibility is in good agreement with the requirements of IMPCA2:98. Appearance: No analytical problems were observed. All labs agreed about the appearance of sample 688, which is clear and free of suspended matter. The way of reporting varies strongly and could be improved. Isopropanol: iis6c15 - X page 6 of 29

7 App. Density: This determination is not problematic. No results were outside the reproducibility limits and the calculated reproducibility is in good agreement with the requirements ASTM D 452:2e1. Colour Pt/Co: No analytical problems were observed. No results were found outside the reproducibility limits. The observed reproducibility is in agreement with the requirements of ASTM D 129:5. 2 o C: No analytical problems were observed. No results were outside the reproducibility limits and the observed reproducibility is in good agreement with the requirements of ASTM D 452:2e1. Distillation: This determination is not problematic. For IBP and DP, no results were outside the reproducibility limits. The calculated reproducibilities for both IBP and DP are in agreement with the requirements of ASTM D 178:5 for the manual mode and the automated mode. NVM: This determination is not problematic. No results were outside the reproducibility limits and the observed reproducibility is in good agreement with the requirements of ASTM D 1353:3. Water: No analytical problems were observed. No results were outside the reproducibility limits and the calculated reproducibility is in good agreement with the requirements of ASTM D 1364:2. Purity: Unfortunately, the methods used do not provide any reproducibility value, therefore no significant conclusions could be drawn. However, the calculated reproducibility is large in comparison with the calculated reproducibility found in the previous proficiency test (iis5c14) of December 25. Purity on dry basis: Unfortunately, the methods used do not provide any reproducibility value, therefore no significant conclusions could be drawn. However, the calculated reproducibility is large in comparison with the calculated reproducibility found in the previous proficiency test (iis5c14) of December 25. Ethanol: Too few numerical results were reported for meaningful conclusions. Only two participants reported a numerical value. n-propanol: This determination is problematic for two participants. Two of the nine results were outside the reproducibility limits. The calculated reproducibility is, after rejection of the statistical outliers, in agreement with the strict estimated reproducibility calculated using the Horwitz equation. Isopropanol: iis6c15 - X page 7 of 29

8 n-butanol: MEK: Other Imp.: This determination maybe very problematic. Three results were outside the reproducibility limits and the calculated reproducibility is not at all in agreement with the rather strict estimated target reproducibility calculated using the Horwitz equation. This determination maybe problematic. One result was outside the reproducibility limits and the calculated reproducibility is not in agreement with the rather strict estimated target reproducibility calculated using the Horwitz equation. The results reported for this parameter vary over a rather large range: between mg/kg. This might be explained by the large variety of methods used (see appendix 2) and the definition of the term other impurities. To obtain optimum results each component should be identified and calculated using the appropriate response factor. 4.2 PERFORMANCE EVALUATION FOR THE GROUP OF LABORATORIES A comparison has been made between the reproducibility as declared by the relevant standard and the reproducibility as found for the group of participating laboratories that participated. The reproducibilities derived from literature standards (in casu ASTM standards) and the calculated reproducibilities of sample 688 are compared in the next table. Parameter unit n average 2.8 * sd R (lit) Acidity as acetic acid %M/M Anorganic Chloride mg/kg Appearance 12 n.a. n.a. n.a. Apparent Density 2ºC kg/l Colour Pt/Co ºC kg/l Initial Boiling Point C Dry Point C Nonvolatile Matter mg/1ml Water %M/M Purity %M/M Unknown Purity on dry basis %M/M Unknown Ethanol mg/kg 2 n.a. n.a. n.a. n-propanol mg/kg n-butanol mg/kg Methyl-Ethyl-Ketone mg/kg Other Impurities mg/kg Unknown Table 4: Reproducibilities for sample 688 Isopropanol: iis6c15 - X page 8 of 29

9 Without further statistical calculations it can be concluded that for many tests there is a not a good compliance of the group of participants with the relevant standards. The tests that are problematic have been discussed in paragraph COMPARISON OF THE PROFICIENCY TEST OF NOVEMBER 26 WITH THE PREVIOUS PT. November 26 December 25 February 25 Number of reporting labs Number of results reported Statistical outliers Percentage outliers 6.5 % 5.2 % 7.3 % Table 5: comparison with previous proficiency tests In proficiency tests outlier percentages of 3 % % are quite normal. The performance of the determinations of the proficiency tests was compared against the requirements of the respective standards. The conclusions are given the following table: Determination November 26 December 25 February 25 Acidity as acetic acid Anorganic Chlorides as Cl ++ n.e. -- Apparent 2 C Colour Pt/Co o C Initial Boiling Point Dry Point Nonvolatile Matter Water Purity - (++) (--) Purity on dry basis - (++) (--) Ethanol n.e n-propanol n-butanol Methyl-Ethyl-Ketone Table 6: comparison determinations against the standard requirements The performance of the determinations against the requirements of the respective standards is listed in the above table. The following performance categories were used: ++: group performed much better than the standard + : group performed better than the standard +/-: group performance equals the standard - : group performed worse than the standard -- : group performed much worse than the standard n.d.: not determined n.e.: not evaluated Isopropanol: iis6c15 - X page 9 of 29

10 APPENDIX 1 Determination of Acidity as Acetic Acid on sample 688; results in %M/M. D D D D D D DG(.1) D D D D DG(.1) D D normality OK n 1 outliers 2 mean (n).7 st.dev. (n).14 R(calc.).4 R(D 1613:6) Kernel Density Isopropanol: iis6c15 - X page 1 of 29

11 Determination of Anorganic Chloride as Cl on sample 688; results in mg/kg. INHOUSE IMPCA INHOUSE IMPCA 2 < INHOUSE POTH normality not OK n 5 outliers mean (n).115 st.dev. (n).176 R(calc.).31 R(IMPCA2:98) Isopropanol: iis6c15 - X page 11 of 29

12 Determination of Appearance on sample 688; VISUAL C&F VISUAL C&F INHOUSE C&F VISUAL CFFMIS VISUAL CFFMIS VISUAL B&C VISUAL CLWFP D29 B&C VISUAL CLFFSM VISUAL CFFSM VISUAL B&C VISUAL C&F normality n.a. n 12 outliers n.a. mean (n) n.a. st.dev. (n) n.a. R(calc.) n.a. R(Visual) n.a. Abbreviations: B&C = Bright and Clear C&F = Clear and Free CFFMIS = Clear and Free From Matter In Suspension CLWFP = Clear Liquid With a Few Particles CLFFSM = Clear Liquid Free From Suspended Matter CFFSM = Clear and Free From Suspended Matter Isopropanol: iis6c15 - X page 12 of 29

13 Determination of Apparent Density 2 ºC on sample 688; results in kg/l. D D D D D D G(.5) CALC D normality OK n 7 outliers 1 mean (n) st.dev. (n).76 R(calc.).21 R(D 452:2e1) Kernel Density Isopropanol: iis6c15 - X page 13 of 29

14 Determination of Colour Pt/Co scale on sample 688; D D INHOUSE D 129 < D D 129 < D 129 < D D D D D 129 < D D normality not OK n 1 outliers mean (n) 2.7 st.dev. (n) 1.6 R(calc.) 3. R(D 129:5) Kernel Density Isopropanol: iis6c15 - X page 14 of 29

15 Determination of Density at 2 o C on sample 688; results in kg/l. D D D D D D G(.5) D D D D D IP D normality not OK n 12 outliers 1 mean (n) st.dev. (n).85 R(calc.).24 R(D 452:2e1) Kernel Density Isopropanol: iis6c15 - X page 15 of 29

16 Determination of 76 mmhg on sample 688; results in C. D 178-A D 178-A D 178-A D 178-M D 178-A D 178-A D 178-M 81.4 G(.1) D 178-M D 178-A D 178-A D 178-M normality not OK n 1 outliers 1 mean (n) st.dev. (n).67 R(calc.).19 R(D 178:5-A) 1.28 R (D 178:5-M) = Kernel Density Isopropanol: iis6c15 - X page 16 of 29

17 Determination of 76 mmhg on sample 688; results in C. D 178-A D 178-A D 178-A D 178-M D 178-A D 178-A D 178-M D 178-M D 178-A 83.1 C 1.79 First reported D 178-A D 178-M normality OK n 11 outliers mean (n) st.dev. (n).287 R(calc.).8 R(D 178:5-A).88 R (D 178:5-M) = Kernel Density Isopropanol: iis6c15 - X page 17 of 29

18 Determination of Nonvolatile Matter on sample 688; results in mg/1 ml. D D D D 1353 < D 1353 < D D D D 1353 < All results (*): normality OK OK n 6 9 outliers mean (n) st.dev. (n) R(calc.) R(D 1353:3) *) In the calculation of the mean, standard deviation, the reproducibilities and below graph, a reported value of <x ppm is changed into x/2. All results (*) Kernel Density Isopropanol: iis6c15 - X page 18 of 29

19 Determination of Water content on sample 688; results in %M/M. D D D D E D E D D D D D D normality not OK n 13 outliers mean (n).447 st.dev. (n).299 R(calc.).84 R(D 1364:2) Kernel Density Isopropanol: iis6c15 - X page 19 of 29

20 Determination of Purity on sample 688; results in %M/M. GC GC INHOUSE INHOUSE INHOUSE INHOUSE GC C First reported INHOUSE normality OK n 8 outliers mean (n) st.dev. (n).226 R(calc.).63 R(lit) Unknown Compare R(iis5C14) = Kernel Density Isopropanol: iis6c15 - X page 2 of 29

21 Determination of Purity on dry basis on sample 688, results in %M/M. GC GC INHOUSE INHOUSE INHOUSE INHOUSE GC C First reported INHOUSE INHOUSE normality OK n 9 outliers mean (n) st.dev. (n).196 R(calc.).55 R(lit) Unknown Compare R(iis5C14) = Kernel Density Isopropanol: iis6c15 - X page 21 of 29

22 Determination of Ethanol content on sample 688; results in mg/kg. GC < GC INHOUSE < INHOUSE < INHOUSE INHOUSE < GC < INHOUSE < INHOUSE < All results (*): normality n.a. OK n 2 7 outliers 2 mean (n) n.a. 3.5 st.dev. (n) n.a R(calc.) n.a. 4.8 R(Horwitz) n.a. 1.8 *) In the calculation of the mean, standard deviation, the reproducibilities and below graph, a reported value of <x ppm is changed into x/2. All results (*).12.1 Kernel Density of all results (*) Isopropanol: iis6c15 - X page 22 of 29

23 Determination of n-propanol on sample 688; results in mg/kg. GC GC INHOUSE INHOUSE INHOUSE 5 C,DG(.1) -8.3 First reported <1 357 INHOUSE GC INHOUSE INHOUSE 3.8 DG(.1) normality not OK n 7 outliers 2 mean (n) st.dev. (n) 5.77 R(calc.) 16.2 R(Horwitz) Kernel Density Isopropanol: iis6c15 - X page 23 of 29

24 Determination of n-butanol on sample 688; results in mg/kg. GC GC INHOUSE INHOUSE INHOUSE INHOUSE < GC < INHOUSE INHOUSE normality OK n 7 outliers mean (n) 13.2 st.dev. (n) 9.27 R(calc.) 26. R(Horwitz) Isopropanol: iis6c15 - X page 24 of 29

25 Determination of Methyl-Ethyl-Ketone on sample 688; results in mg/kg. GC GC INHOUSE INHOUSE INHOUSE < GC < INHOUSE INHOUSE normality not OK n 6 outliers mean (n) 7.25 st.dev. (n) R(calc.) 4.3 R(Horwitz) Isopropanol: iis6c15 - X page 25 of 29

26 Determination of Other Impurities on sample 688; results in mg/kg. GC GC INHOUSE INHOUSE INHOUSE 14 C First reported INHOUSE GC 472 C First reported INHOUSE INHOUSE normality OK n 9 outliers mean (n) st.dev. (n) R(calc.) R(lit) Unknown Kernel Density Isopropanol: iis6c15 - X page 26 of 29

27 APPENDIX 2 Gaschromatographic conditions Lab Column type Temp.program Rate Calib. RF-factor Recovery DB-1 5 C - 2 C (5 C/min.) Int.std. 1 No CPSIL 5 CB 5 C - 15 C 8 min.hold/5 C Int.std. 1 No CPSIL 5 CB 5min. 4 C - 12 C 1min. (1 C/min.) Int.std. 1. No 323 DB-1 [6m.32mm 1µm] 1min. 35 C - 15 C (7 C/min.) Ext.std..75 Yes Ext.std No 357 HP-1 [6m.32mm 1µm] 12min. 35 C - 2 C 1min. (6 C/min.) Norm. 1 Yes No 867 HP-1 [1m.25mm.5µm] 5min. 4 C - 15 C 1min. (5 C/min.) Int.std. 1 No CPSIL Int.std. 1. Yes Isopropanol: iis6c15 - X page 27 of 29

28 APPENDIX 3 List of participants Name Contry 2 laboratories in AUSTRALIA 1 laboratory in BELGIUM 1 laboratory in FINLAND 1 laboratory in MEXICO 1 laboratory in P.R. of CHINA 2 laboratories in SPAIN 1 laboratory in TAIWAN R.O.C. 2 laboratories in THE NETHERLANDS 1 laboratory in U.A.E. 2 laboratories in U.S.A. 1 laboratory in UNITED KINGDOM Isopropanol: iis6c15 - X page 28 of 29

29 APPENDIX 4 Abbreviations: C U D(.1) D(.5) G(.1) G(.5) DG(.1) DG(.5) EX E n.a. W = final result after checking of first reported suspect result = reported in wrong unit = outlier in Dixon s outlier test = straggler in Dixon s outlier test = outlier in Grubbs outlier test = straggler in Grubbs outlier test = outlier in Double Grubbs outlier test = straggler in Double Grubbs outlier test = excluded from calculations = error in calculations = not applicable = withdrawn on request participant Literature: 1 i.i.s. Interlaboratory Studies, Protocol for the Organisation, Statistics & Evaluation, November 23 2 Defence Standard 91-91, Issue 5 Publication date 8 February ASTM E ASTM E ISO 5725, parts 1-6, M. Thompson and R. Wood, J. AOAC Int, 76, 926, (1993) 7 W.J. Youden and E.H. Steiner, Statistical Manual of the AOAC, (1975) 8 IP 367/84 9 DIN 3842 T41/42 1 P.L. Davies, Fr. Z. Anal. Chem, 331, 513, (1988) 11 J.N. Miller, Analyst, 118, 455, (1993) 12 Analytical Methods Committee Technical Brief, No4 January The Royal Society of Chemistry 22, Analyst 22, 127 page , P.J. Lowthian and M. Thompson. (see Isopropanol: iis6c15 - X page 29 of 29