Proficiency Test Report

Transcription

1 Smokeless Tobacco Sub-Group Proficiency Test Report The Determination of Arsenic, Beryllium, Cadmium, Chromium, Cobalt, Nickel, Lead, and Selenium in Reference Materials September 2015 Author and Sub-Group Secretary: Karl Wagner, Ph.D. Altria Client Services Co-Author and Statistical Analysis: Michael Morton, Ph.D. Altria Client Services

2 Table of Contents 1. Summary Introduction Organisation Participants Protocol Data Descriptive Statistics Data Statistical Analysis Results Z-Scores Conclusion APPENDIX A: Study Protocol APPENDIX B: Data Tables... 18

3 1. Summary In December 2014 through March 2015, the CORESTA Smokeless Tobacco Sub-Group (STS) and Routine Analytical Chemistry Sub-Group (RAC) conducted a proficiency study to determine arsenic (As), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), nickel (Ni), lead (Pb), and selenium (Se) in three certified reference materials and in a CORESTA Reference Product (CRP3). Nineteen laboratories participated in this study. 2. Introduction The objective of this proficiency study was to provide an initial assessment of laboratory capabilities for the analysis of specific trace elements in several tobacco and non-tobacco plant matrices. Laboratories were requested to determine As, Be, Cd, Cr, Co, Ni, Pb, and Se using inductively coupled plasma mass spectrometry (ICP-MS). 3. Organisation 3.1 Participants A list of the participating laboratories is provided in Table 1. The laboratories are listed in alphabetical order. The laboratory codes used in this report do not correspond to the same order as provided in Table 1. Table 1: List of Participating Laboratories Arista Laboratories, United States Participating Laboratories British American Tobacco, Souza Cruz S.A, Brazil Canadian Border Service Agency, Canada China National Tobacco Quality Supervision and Test Center, China Centers for Disease Control and Prevention, Tobacco Products Laboratory, United States Enthalpy Analytical, United States Essentra Scientific Services, United Kingdom Eurofins Food & Agro Testing, Sweden Global Laboratory Services, United States Imperial Tobacco Group, Reemtsma, Germany Imperial Tobacco Group, SEITA, France Japan Tobacco, Leaf Tobacco Research Center, Japan KT&G R&D Center, Republic of Korea Labstat International, Canada Lorillard Tobacco Company, United States Philip Morris International TPTL, Switzerland R.J. Reynolds Tobacco Company, United States Swedish Match, Sweden Technical Center of Shanghai Tobacco Group Co., LTD Shanghai, China STS-CTR-Metals Proficiency Study September /21

4 3.2 Protocol The study included three certified reference materials and CRP3. Sample descriptions are provided in Table 2. The two tobacco reference materials do not contain significant levels of Se; therefore, BCR 402 (White Clover) was included as this plant matrix has significant levels of Se. Participating laboratories were responsible for procuring the samples for the study. Each participant was requested to determine three replicates under repeatability conditions, using their validated method. Data were reported on an as-is basis and not corrected for moisture. A microwave digestion method was provided for reference, but use of the digestion method was not required. Additional details are provided in the study protocol which is given in Appendix A. The only deviation noted by the participants was that Lab 3 used ICP-OES instead of ICP-MS. Table 2: Sample Identification Sample INCT-OBTL-5 INCT-PVTL-6 BCR-402 CRP3 Product Type Oriental Basma Tobacco Leaves Polish Virginia Tobacco Leaves White Clover CORESTA Reference Product 3, American-style loose dry snuff powder 4. Data Descriptive Statistics The data tables, with descriptive statistics, are provided in Appendix B. provided on an as-is basis without any correction for moisture. The data are 5. Data Statistical Analysis The assigned values for each element, for each sample, were developed from the certified or informational values provided in the certificates of analysis, if available. If certified or informational values were not available, the assigned values were the median values from this study. The certified and informational values provided in the certificates of analysis were given on a dry weight basis; however, the results in this study were expressed on an as-is basis. For this reason, the dry weight values from the certificates of analysis were converted to an as-is basis. The conversion to an as-is basis was based on moisture measurements (oven volatiles) made by three participating laboratories. The average percent moisture values of the reference materials, determined by the three laboratories, are given in Table 3. Table 3: Percent Oven Volatiles Sample Average Percent Moisture INCT-OBTL-5 4.6% INCT-PVTL-6 3.8% BCR % CRP3 Not determined STS-CTR-Metals Proficiency Study September /21

5 It was necessary to determine the standard deviations for the proficiency assessment in order to calculate z-statistics. The standard deviations were calculated from the Horwitz equation and are presented in Table 4. The Horwitz equation was originally developed by William Horwitz based on the observation that over a wide concentration range, the interlaboratory variation can be approximated by an exponential function of the concentration of the analyte. The equation has been refined, since its original introduction and we use the version of the equation given in Thompson 1. The updated version of the Horwitz equation used here is given as: σ p = 0.01 c, 13.8% c σ p = 0.02c , 120 ng g c < 13.8% σ p = 0.22c, c < 120 ng g Where: σp: The standard deviation for proficiency assessment. c: The concentration of the element on a gram of analyte per gram sample basis. The concentration used in the calculation was the assigned value. The standard deviations are given in Table 4. Z-statistics were calculated for each laboratory to assess the lab performance. The z-statistic is defined as: z = x x a σ p Where: x: The value obtained by the laboratory xa: The assigned value based on the certified or informational value if available, or on the study median. σp: The standard deviation for proficiency assessment. The z-statistics (z-scores) are presented in the Results section. 1 Thompson, Michael, Recent trends in inter-laboratory precision at ppb and sub-ppb concentrations in relation to fitness for purpose criteria in proficiency testing, The Analyst, 2000, 125, STS-CTR-Metals Proficiency Study September /21

6 Table 4: Assigned Values Certified or Informational Value (dry weight) Assigned Value (as-is) INCT-OBTL-5 (ng/g) As C Be I Cd C Cr I Co C Pb C Ni C Se M St dev (as-is) ǂ Certified or Informational Value (dry weight) Assigned Value (as-is) INCT-PVTL-6 (ng/g) As C Be M Cd C Cr I Co C Pb C Ni C Se M St dev (as-is) ǂ Certified or Informational Value (dry weight) Assigned Value (as-is) BCR-402 (ng/g) As C Be M Cd M Cr I Co C Pb M Ni I Se C St dev (as-is) ǂ Certified or Informational Value (dry weight) Assigned Value (as-is) CRP3 (ng/g) As M Be M Cd M Cr M Co M Pb M Ni M Se M St dev (as-is) ǂ C: The assigned value was based upon the certified value provided in the certificate of analysis. I: The assigned value was based upon the informational value provided in the certificate of analysis. M: The assigned value was based upon the group median. ǂ : The standard deviations were calculated from the Horwitz equation. --: Certified or informational values are not available. 6. Results Z-Scores The values obtained by each laboratory, for each element, are given in Appendix B. The corresponding z-statistics are given in Tables 5 8. As a general rule, the z-scores are regarded as reasonable if -2 < z < 2 and generally thought to be unacceptable if z >3. Laboratories should consider z between 2 and 3 as a warning signal. STS-CTR-Metals Proficiency Study September /21

7 Table 5: Z-Score Results for INCT-OBTL-5 Lab # As C Be I Cd C Cr I Co C Pb C Ni C Se M ND <LOD ND ND <LOD <LOD <LOD <LOD ND ND ND ND ND ND ND ND ND ND ND ND -0.6 ND C: The assigned value was based upon the certified value provided in the certificate of analysis. I: The assigned value was based upon the informational value provided in the certificate of analysis. M: The assigned value was based upon the group median. ND: the element was not determined by the laboratory <LOD: Signifies the analyte was below the LOD specified by the laboratory STS-CTR-Metals Proficiency Study September /21

8 Table 6: Z-Score Results for INCT-PVTL-6 Lab # As C Be M Cd C Cr I Co C Pb C Ni C Se M ND <LOD <LOD ND ND <LOD <LOD <LOD <LOD <LOD <LOD <LOD 14 ND ND ND ND ND ND ND ND <LOD ND ND ND ND 1.2 ND <LOD C: The assigned value was based upon the certified value provided in the certificate of analysis. I: The assigned value was based upon the informational value provided in the certificate of analysis. M: The assigned value was based upon the group median. ND: the element was not determined by the laboratory <LOD: Signifies the analyte was below the LOD specified by the laboratory STS-CTR-Metals Proficiency Study September /21

9 Table 7: Z-Score Results for BCR-402 Lab # As C Be M Cd M Cr I Co C Pb M Ni I Se C <LOD ND <LOD ND ND <LOD <LOD <LOD <LOD ND ND ND ND ND ND ND ND <LOD ND ND ND ND -1.2 ND <LOD C: The assigned value was based upon the certified value provided in the certificate of analysis. I: The assigned value was based upon the informational value provided in the certificate of analysis. M: The assigned value was based upon the group median. ND: the element was not determined by the laboratory <LOD: Signifies the analyte was below the LOD specified by the laboratory STS-CTR-Metals Proficiency Study September /21

10 Table 8: Z-Score Results for CRP3 Lab # As M Be M Cd M Cr M Co M Pb M Ni M Se M ND <LOD ND ND <LOD <LOD ND ND <LOD ND ND ND ND -1.5 ND M: The assigned value was based upon the group median. ND: the element was not determined by the laboratory <LOD: Signifies the analyte was below the LOD specified by the laboratory STS-CTR-Metals Proficiency Study September /21

11 7. Conclusion The overall results of the proficiency study, showing the percentage of acceptable results where z 2, are given in Table 9. Notable observations include the following: The results demonstrate that participating laboratories showed the least agreement with the determination of selenium in all samples. It is worth noting that the z score results for selenium also show the greatest deviation from z =2 as compared to the other elements (e.g. z=54.6 for CRP3). Laboratories also showed poor agreement with the certified values for chromium in INCT-OBTL-5 and INCT-PVTL-6. The median value of chromium among the participating laboratories was close to two standard deviations below the assigned values for both samples. Although most laboratories showed acceptable results for lead with values within two standard deviations of the assigned value, the median of the lab values for lead for INCT-PVTL-6 was just over 1.6 standard deviations below the assigned value. A recommendation for future metals studies is that all laboratories report data for the certified reference materials on a dry weight basis so that these data do not need to be converted to an as-is basis. Moisture (oven volatiles) should be determined following the instruction provided in the certificate of analyses. Table 9: Proficiency Study Results Element Assigned Value (ng/g) Number of Scores z 2 Total Number of Scoresǂ Percent z 2 INCT-OBTL-5 As C Be I Cd C Cr I Co C Pb C Ni C Se M INCT-PVTL-6 As C Be M Cd C Cr I Co C Pb C Ni C Se M STS-CTR-Metals Proficiency Study September /21

12 Element Assigned Value (ng/g) Number of Scores z 2 Total Number of Scoresǂ Percent z 2 BCR-402 As C Be M Cd M Cr I Co C Pb M Ni I Se C CRP3 As M Be M Cd M Cr M Co M Pb M Ni M Se M C: The assigned value was based upon the certified value provided in the certificate of analysis. I: The assigned value was based upon the informational value provided in the certificate of analysis. M: The assigned value was based upon the group median. ǂ: Laboratories that reported <LOD or did not determine the element in the matrix were not included in the sum. STS-CTR-Metals Proficiency Study September /21

13 APPENDIX A: Study Protocol SMOKELESS TOBACCO SUB-GROUP Metals Proficiency Study Protocol December 3, 2014 Author and Study Coordinator: Karl Wagner (Altria Client Services Inc.), U.S.A. Co-Author Statistical Analysis: Michael Morton, Ph D. (Altria Client Services Inc.), U.S.A. Confidentiality Notice: All data in this Collaborative Study should be handled in the strictest of confidence by all participating laboratories. STS-CTR-Metals Proficiency Study September /21

14 1. Introduction The purpose of interlaboratory proficiency testing is to provide participating laboratories with an objective means of assessing laboratory capability. Additionally, proficiency testing is an important component of a quality system and is a requirement of ISO Objective The objective of this proficiency study is to provide an initial assessment of laboratory capabilities for the analysis of specific trace elements in several certified reference materials and in CORESTA Reference Product 3 (CRP3). Arsenic, Beryllium, Cadmium, Chromium, Cobalt, Lead, Nickel, and Selenium will be determined in the matrices using inductively coupled plasma mass spectrometry (ICP-MS). 3. Time schedule Date Activity November 25, 2014 December 3, 2014 March 1, 2015 April 29, Participating Laboratories Laboratories state their intention to participate and order standard reference materials Finalize protocol and distribute Laboratories submit results by this date Discuss results at STS meeting in Hangzhou, China The following laboratories have kindly agreed to take part in the study: Altria Client Services Arista Laboratories 2015 Metals Proficiency Study Participants British American Tobacco, Souza Cruz S.A China National Tobacco Quality Supervision and Test Center Enthalpy Analytical Essentra Scientific Services Eurofins Food & Agro Testing, Sweden Global Laboratory Services Japan Tobacco, Inc. Imperial Tobacco Group, Reemtsma Imperial Tobacco Group, SEITA KT&G R&D Center Labstat International Lorillard Tobacco Company STS-CTR-Metals Proficiency Study September /21

15 2015 Metals Proficiency Study Participants Microbac Laboratories, Wilson Philip Morris International, Brazil Philip Morris International, Neuchâtel (PPQ, OC Lab) PT HM Sampoerna, Tbk R.J. Reynolds Tobacco Company Shanghai Tobacco Group Co., Ltd Swedish Match Northern Europe 5. Samples 5.1 Selection 1) Oriental Basma Tobacco Leaves (INCT-OBTL-5) 2) Polish Virginia Tobacco Leaves (INCT-PVTL-6) 3) White Clover (BCR-402) 4) CRP3 The three reference materials are available from LGC Standards ( CRP3 is available from North Carolina State University. Note that different versions of the certified tobacco materials were available in the past. Please ensure that you use the correct version for this study (INCT-OBTL-5 and INCT- PVTL-6). Earlier versions of these materials will have different suffixes and are not suitable. 5.2 Storage The three standard reference materials should be stored as specified by the distributer. CRP3 should be stored at 20 C). 6. Analysis 6.1 Analytes The following analyses should be determined by each participating laboratory using ICP-MS: Arsenic, Beryllium, Cadmium, Chromium, Cobalt, Lead, Nickel, and Selenium. 6.2 Methods Laboratories should use their in house instrumental method. A closed vessel microwave digestion procedure is provided in Appendix A for reference; however, use of the procedure is not a requirement for this study. 6.3 Replicates Conduct three (3) independent replicate preparations per sample. STS-CTR-Metals Proficiency Study September /21

16 7. Data Reporting 1) The analytes should be reported in units of ng/g, on an as-is basis. 2) Data above the LOD, but below the LOQ should be reported and footnoted to indicate the value was below the LOQ, but above the LOD. 3) If the instrumental result is less than the LOD, the numerical LOD should be reported with a < symbol (e.g. <0.201). The completed data sheet, provided below, should be sent to karl.a.wagner@altria.com. Microsoft Excel Worksheet 8. Statistical Analysis Data for the certified reference materials will be compared to the certified values or reference values, if available. Z-Scores will also be calculated for all samples. 9. Presentation of the Results The final output will be a presentation for discussion at the spring STS meeting which is scheduled to be held in Hangzhou, China on April 29, Protocol Appendix A: Proposed Closed Vessel Microwave Digestion Procedure 1. Sample Preparation 1.1. At the time of analysis, samples should be allowed to equilibrate to room temperature before weighing Samples should be ground to a particle size of less than 1mm before digestion. 2. Sample digestion 2.1. Closed vessel microwave assisted acid digestion is used for the digestion of organic material. This method should be regarded as a basic guideline for developing a digestion procedure and not standard operating procedure. The manufacturer s instructions for the microwave digestion unit should be consulted before developing a digestion method. This method will not dissolve refractory samples such as silicates and may exhibit poor recovery for analytes bound in such matrices. The goal of this digestion procedure is to digest the organic matrix in the sample using nitric acid by maintaining a temperature of 200 C.Using an analytical balance, weigh approximately 0.5g of sample into a microwave digestion vessel and record the weight to the nearest 0.1 mg. If a pouched product is analysed, unit pouches should be weighed for digestion. STS-CTR-Metals Proficiency Study September /21

17 Note: The LOQ will be affected by the amount of tobacco digested. Some samples may react more vigorously to the digestion procedure. In these cases, the sample weights and /or digestion procedure will need to be adjusted accordingly Add 5.0±0.1 ml of nitric acid and gently swirl the sample being careful not to deposit the sample on the vessel wall Screw the cap onto the digestion vessel and either leave the lid loose or leave the vent cap loose to let digestion gases escape. Let the samples predigest in an exhaust hood for a minimum of 1 hour and up to overnight before proceeding to the microwave. The sample should no longer be effervescent when the vessel is sealed Tighten the digestion vessel cap and the vent cap. Place the microwave vessels into the microwave and enter a digestion program based on manufacturer s specifications in order to reach a temperature of 150 C over a period of 15 minutes. Allow the samples to cool and then remove the vessels from the microwave unit and open the vessels to vent them Reseal the vessels and place the microwave vessels into the microwave and enter a digestion program based on manufacturer s specifications in order to reach a temperature of 200 C over a period of 15 minutes. Maintain 200 C for an additional 15 minutes. Allow the samples to cool and then remove them from the microwave Quantitatively transfer the contents of each vessel to a 100mL graduated, polypropylene vial or flask. Carefully rinse the digestion vessel with Type 1 water and add to the polypropylene vial. Dilute the samples to 100mL final volume with Type 1 water. Cap the samples and mix well The samples will have a final nitric acid concentration of approximately 5%. The calibration standard used for analysis should also have a final nitric acid concentration of 5%. STS-CTR-Metals Proficiency Study September /21

18 APPENDIX B: Data Tables INCT-OBTL-5 (ng/g, as-is basis) Lab # As C Be I Cd C Cr I Co C Pb C Ni C Se M Assigned Value ± ± ± ± ± ± ± ± ± ± ± ± 155 ND 1770 ± ± ± ± ± ± ± ± ± ± 414 < ± 79 ND 3454 ± ± 481 ND 1882 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 9 43 ± ± ± ± ± ± ± ± ± ± ± ± ± ± 257 < ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 19 < ± ± ± ± ± ± ± ± ± 49 < ± ± ± ± ± 416 < ± ± ± ± ± ± ± ± ND ND ND ND ND ND ND ND ± ± ± ± ± ± ± ± ± ǂ 2711 ± ± ± ± ± ± ± 27 ND 3100 ± ± 430 ND 2018 ± ± ± ± 40 ND 3075 ± ± ± 56 ND 7577 ± 456 ND ± ± ± ± ± ± ± ± 216 C: The assigned value was based upon the certified value provided in the certificate of analysis. This value was converted to an as-is basis. I: The assigned value was based upon the informational value provided in the certificate of analysis. This value was converted to an as-is basis. M: The assigned value was based upon the group median. ǂ: Only one replicate was above the LOD; therefore, a standard deviation was not calculated ND: the element was not determined by the laboratory < Symbol: Signifies the analyte was below the LOD specified by the laboratory STS-CTR-Metals Proficiency Study September /21

19 INCT-PVTL-6 (ng/g, as-is basis) Lab # As C Be M Cd C Cr I Co C Pb C Ni C Se M Assigned Value ± ± ± ± ± ± ± 3 74 ± ± ± ± ± 40 ND 661 ± ± 4 38 ± 3 3 < ± ± ± ± ± ± 30 < ± 17 ND 3027 ± ± 61 ND 726 ± ± ± ± ± ± ± ± ± ± ± ± 8 < ± ± ± ± ± ± ± 2 11 ± ± ± ± ± ± ± ± ± ± ± ± ± ± 14 < ± ± ± ± ± ± ± ± ± 4 < ± ± ± ± ± 63 < ± ± ± ± ± ± ± ± ± 5 < ± ± ± ± ± 65 < ± ± ± ± ± ± ± 17 < ND ND ND ND ND ND ND ND ± ± ± ± ± ± ± ± ± 34 < ± ± ± ± ± ± ± 3 ND 2599 ± ± 125 ND 686 ± ± ± ± 14 ND 2595 ± ± ± 21 ND 1693 ± 505 ND ± 60 < ± ± ± ± ± ± 106 C: The assigned value was based upon the certified value provided in the certificate of analysis. This value was converted to an as-is basis. I: The assigned value was based upon the informational value provided in the certificate of analysis. This value was converted to an as-is basis. M: The assigned value was based upon the group median. ND: the element was not determined by the laboratory < Symbol: Signifies the analyte was below the LOD specified by the laboratory STS-CTR-Metals Proficiency Study September /21

20 BCR-402 (ng/g, as-is basis) Lab # As C Be M Cd M Cr I Co C Pb M Ni I Se C Assigned Value ± 10 < ± ± ± ± ± ± ± ± ± ± 150 ND 490 ± ± ± < ± ± ± ± ± ± ± ± 6 ND 210 ± ± 399 ND 479 ± ± ± ± ± ± ± ± ± ± ± ± 13 < ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 9 < ± ± ± ± ± ± ± ± ± ± ± ± ± ± <61 < ± ± ± ± ± ± ± ± ± ± ± ± ± ± ND ND ND ND ND ND ND ND ± ± ± ± ± ± ± ± ± 11 < ± ± ± ± ± ± ± 17 ND 219 ± ± 856 ND 461 ± ± ± ± 9 ND 271 ± ± ± 12 ND 6566 ± 245 ND ± 104 < ± ± ± ± ± ± 382 C: The assigned value was based upon the certified value provided in the certificate of analysis. This value was converted to an as-is basis. I: The assigned value was based upon the informational value provided in the certificate of analysis. This value was converted to an as-is basis. M: The assigned value was based upon the group median. ND: the element was not determined by the laboratory < Symbol: Signifies the analyte was below the LOD specified by the laboratory STS-CTR-Metals Proficiency Study September /21

21 CRP3 (ng/g, as-is basis) Lab As M Be M Cd M Cr M Co M Pb M Ni M Se M Assigned Value ± ± ± ± ± ± ± ± ± ± ± ± 406 ND 794 ± ± ± ± ± ± ± ± ± ± 137 < ± 11 ND 1815 ± ± 1058 ND 770 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 5 19 ± ± ± ± ± ± ± ± 8 23 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 5 < ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 28 < ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 9 ND 1363 ± ± 66 ND 787 ± ± ± ± ± ± ± ± ± ± ± ± 16 < ± ± ± ± ± ± ± 10 ND 1597 ± ± 745 ND 805 ± ± ± ± 33 ND 1357 ± ± ± 118 ND 5482 ± 754 ND ± ± ± ± ± ± ± ± 431 C: The assigned value was based upon the certified value provided in the certificate of analysis. This value was converted to an as-is basis. I: The assigned value was based upon the informational value provided in the certificate of analysis. This value was converted to an as-is basis. M: The assigned value was based upon the group median. ND: the element was not determined by the laboratory < Symbol: Signifies the analyte was below the LOD specified by the laboratory STS-CTR-Metals Proficiency Study September /21