Determination of thermal degradants in e-cigarette fluid via direct sample introduction (DSI) gas chromatography-tandem mass spectrometry

Electronic cigarettes (EC) and other electronic nicotine delivery systems (ENDS) have recently become popular choices for nicotine consumption due to the lower perceived harm compared to conventional tobacco products. Currently, only nicotine levels in EC fluids are regulated by the FDA. Besides nicotine and solvents such as propylene glycol and glycerin, the heating of EC fluids may produce thermal degradants that could impact a user's health. We proposed to use direct sample introduction (DSI) GC-MS/MS as a fast and reliable instrumental method to analyze EC fluid components and their thermal degradants generated in a simulated ENDS-like environment within the DSI enclosure. DSI GC-MS/MS separates and detects the target analytes even in the presence of a complex, viscous, and often “dirty” sample matrix. DSI utilizes a programmable-temperature vaporization (PTV) injector in conjunction with a ChromatoProbe accessory, in which a solid or liquid sample in a disposable glass vial can be heated and vapors introduced into the GC column for separation. DSI was used to mimic the heating behavior of an EC atomizer and introduce the EC vapors and degradants into GC-MS/MS in almost real-time. Subsequently, through tandem mass spectrometry, signature ion fragments for thermal breakdown components (e.g. aldehydes) were detected and quantified. Relative peak ratios of those thermal breakdown products and an internal standard were employed to study the effects of temperature ramp rate, maximum heating temperature, and maximum temperature hold time on the outcomes of thermal degradation.