A comparison of levels of nicotine and cotinine in hair of tobacco smokers and users of e-cigarettes using GC-MS

Abstract

The objective of this research project was to develop and validate an analytical method for the determination of nicotine and cotinine in hair samples. Following analysis, a comparison was made in the levels of nicotine and cotinine found in the hair of e-cigarette and tobacco cigarette smokers. The differences in Environmental Tobacco Smoke exposure were also investigated to determine whether e-cigarettes or tobacco cigarettes result in a greater level of nicotine exposure. A total of 23 hair samples were collected from volunteers, and sectioned as both 0–3 cm overview sections, in addition to 3 × 1 cm segmental analysis (subject to sufficient sample). Hair sections were washed, submitted to methanol sonication, alkaline digestion, liquid-liquid extraction, and clean-up using solid-phase extraction [1] . All samples were submitted to GC-MS/MS using a TRACE 1310 GC coupled to TSQ 8000 Evo tandem mass spectrometer from Thermo Fisher Scientific (Waltham, MA, USA) utilising timed-SRM acquisition. Chromatographic separation was achieved using a Thermo Scientific TraceGOLD TG-5MS (20 m × 0.18 mm, 0.18 μm) column. Mean analysis results obtained are presented in Table 1 . When comparing the relative levels of nicotine and cotinine from tobacco smokers and e-cigarette users, the results indicate that tobacco exposure results in nicotine concentrations, approximately 37% higher than those detected in users of e-cigarettes. Hair from e-cigarette users generally contained a higher level of cotinine in all samples, compared to nicotine. A more effective absorption of nicotine may account for a higher level of metabolite (cotinine) detection in the e-cigarette samples. Results indicate there are higher concentrations of the analytes, nicotine and cotinine, in the untreated hair samples when compared to levels detected treated hair samples. The study also investigated the effect of hair colour; grey, white and blonde hair samples contained lower nicotine and cotinine concentrations than brown or black hair in both tobacco and e-cigarette users. A full method validation was performed, providing an analytical method with a measurement of uncertainty at 18% (at cut-off level), linearity was observed for both nicotine and cotinine up to 8 times the top calibrator and within method validation acceptance criteria of R2 > 0.99. The research indicates the usefulness of hair analysis to assess exposure to nicotine and cotinine. The pattern of results indicates a more effective absorption of nicotine from e-cigarette vapour, when compared to nicotine contained within tobacco smoke. The effective bioavailability may vary as a function of solution pH and other ingredients in the vapour liquid [2] .