METHOD DEVELOPMENT AND VALIDATION: QUANTIFICATION OF METALS IN LIQUIDS AND AEROSOL OF E-CIGARETTES

Transcription

1 METHOD DEVELOPMENT AND VALIDATION: QUANTIFICATION OF METALS IN LIQUIDS AND AEROSOL OF E-CIGARETTES Sandra Otte, Sonja Nowak & Michael Intorp Imperial Tobacco Group; Special Analytes Laboratory Hamburg, Germany CORESTA Congress, Jeju, Korea, 05 October 2015.

2 Introduction E-Cigarettes are also known as Electronic Nicotine Delivery Systems ENDS, e-vapour products or electronic cigarettes Recent increase in popularity of e-cigarettes could be observed over the last years. Upcoming regulations will impact the sector as per rules how to manufacture them and where consumption is allowed, i.e. in the EU Numerous scientific publications raise health-related concerns without providing full details about experimental conditions. 2

3 Introduction Functionality and Analysis * * * * * = Metal containing parts In context with possible organic degradation products, the presence of trace metals in some e-liquids or e-vapour aerosols has been previously reported 1. It is claimed by the authors that transfer from an e-device to the e-liquid might be the source of this contamination. 1 3 M. Williams, A. Villarreal, K. Bozhilov, S. Lin, P. Talbot; PLOS ONE; Volume 8; Issue 3, 2013

4 Introduction Objectives In this study, a method was developed and validated for the quantification of trace concentration levels of metals in e-liquids and e-vapour aerosols according to international guidelines for the following metals: tin, copper, aluminium, nickel iron, silver, and chromium. Furthermore, a systematic investigation of the individual analytical steps during the sample preparation were carried out in order to gain more knowledge about potential contamination sources. 4

5 Experimental Studied material For the present study, a typical e-liquid was designed and analysed together with a commercial available e-liquid product. E-vapour prototypes with different vaporizing techniques, known as clearomizer and cartomizer, and a commercial available e-vapour product were smoked based on CRM 81 2, but with bell shape profile. 3 propylene glycol Smoking regime Puff volume [ml] square shape profile 2 CORESTA recommended method 81: Routine Analytical Machine for E-Cigarette Aerosol, June 2015 Puff frequency [seconds] Puff duration [seconds] CRM x bell shape profile 3 the use of a different puff shape profile is due to technical circumstances and unlikely to change the conclusion of the present study 5

6 Experimental Sample preparation for e-liquid Sample preparation for e-vapour aerosol 0.15 g liquid is weighed Particulate in the aerosol of 180 puffs is trapped by electrostatic precipitation Filled up to 20 ml with13%hno 3 coupled with an impinger (5 ml HNO 3 ) + ISTD (internal standard) Aliquot is analysed by ICP-OES Electrostatic precipitation is washed with 15 ml HNO 3 Impinger and wash solution are combined (total 20 ml) 6

7 Experimental: Target Compounds Wave length (ICP-OES): Compounds Wave length [nm] Tin 189,927 Copper 327,393 Aluminum 396,153 Nickel 232,003 Iron 259,939 Silver 328,068 Chromium 267,716 Yttrium 371,029 Yttrium can be applied as internal standard. 7

8 Results and Discussion Validation study - Linearity, Working Range, Precision Experimental design Solvent solution Spiked with standards (5 concentration levels) Spiked with standard mix level 4 Six replicates per concentration level were carried out to check the linearity Six replicates were carried out for the determination of precision (instrument) Analysis was performed by ICP-OES and results were evaluated. 8

9 Results and Discussion Validation study Standard calibration: Linearity (r), Working Range, Precision (CV %), LOQ, LODin µg/g and µg/10 puffs, resp. : Compound Working range [ng/ml] Regression Coefficient CV% (c=50ng/ml) LOQ* (liquid/vapour) LOD* (liquid/vapour) Tin ,999 2,6 4,5 / 0,04 1,5 / 0,01 Copper ,999 2,9 0,4 / 0,003 0,14 / 0,001 Aluminum ,999 1,3 2,25 / 0,02 0,75 / 0,007 Nickel ,999 0,7 1,5 / 0,01 0,5 / 0,003 Iron ,999 0,6 0,4 / 0,003 0,14 / 0,001 Silver ,999 0,8 0,4 / 0,003 0,14 / 0,001 Chromium ,999 1,1 0,9 / 0,007 0,3 / 0,002 *LOD / LOQ = Limit of Detection (LOD S/N 1:3); Limit of Quantification (LOQ; S/N 1:9) in µg/g and µg/10 puffs 9

10 Results and Discussion Validation study - Recovery / Accuracy, Repeatability Experimental design Solution Solution (Matrix: e-vapour aerosol and e-liquid, resp.) Spiked with standard solutions; medium concentration level six replicates were carried out. Analysis was performed by ICP-OES and results were evaluated. (Blank correction) 10

11 Results and Discussion Validation study * * * * * * = Blank corrected 11

12 Results and Discussion Validation study + * * * * * * = Blank corrected + = CV < 16 % is accepted for concentration levels about 1 ppm (Commission Decision 2002/657/EC). 12

13 Results and Discussion Cartomizer (180 puffs)/ Liquid Compound Sample min - max [µg/10puff] Blank min max [µg/10puff] Liquid [µg/g] Tin <0,04-0,48 <0,04 <4,5 Copper 0,005-0,02 <0,003-0,01 <0,4 Aluminum 0,07-0,83 0,09-0,80 <1,5 Nickel <0,01-0,03 <0,01 <0,7 Iron 0,005-0,03 0,004-0,03 <0,4 Silver <0,003 <0,003 <0,4 Chromium <0,007 <0,007 <0,9 13

14 Results and Discussion Cartomizer: metal yields per 50 puffs No systematic increase of metal yields was observed. In same cases, e.g. nickel and particularly aluminium levels show higher yield variation 14

15 Results and Discussion Clearomizer: metal yields per 50 puffs No systematic increase of metal yields was observed. In same cases, e.g. nickel and particularly aluminium levels show higher yield variation 15

16 Results and Discussion Contamination sources? Compound Solution (standard / extraction) Glass ware (impinger / glass pearls) Electrostatic precipitation (glass) Metal ring Labyrinth seal Tin [ng/ml] <30 / < 30 <30 < <30 Copper [ng/ml] <2,5 <2,5 <2, Aluminum [ng/ml] <15 <15 / 32 < Nickel [ng/ml] <10 / <10 <10 < Iron [ng/ml] <2,5 2,6 / Silver [ng/ml] <2,5 / <2,5 <2,5 <2,5 <2,5 <2,5 Chromium [ng/ml] <6 <6 < Main impact of metal contamination seems to be the metal ring and the seals from the smoking device. 16

17 Summary The validation study showed for e-liquid matrices that the precision and repeatability calculated for the developed method are lower than the acceptable limits set by EU guideline. Acceptable recovery rates were found (about 100%) which verify the accuracy of the measurements for the developed method in e-liquid matrices. Within this particular study, the use of a standard cigarette smoking machine including all its components may have caused contaminations with tin, aluminium, copper, iron and nickel. 17

18 Conclusion The ICP-OES technique is suitable for the determination of the metals in e-liquids and e-vapour aerosols. Devices to generate and collect aerosol from e-cigarette require adaptations to avoid metal contamination from components (i.e. seals). Sources for potential contamination should be given appropriate consideration and should be eliminated to the extent possible when methods are developed to be referenced in potential future regulations. 18

19 Acknowledgements Thanks to Special Analytes Lab Team in Hamburg; in particular Ute Drescher, Claudia John, Annika Krettek, Lars Elster for fruitful discussions and technical support. and you for your kind attention! Visit our Scientific Research website: 19