Headspace analysis of E-cigarette fluids using comprehensive two dimensional GC×GC-TOF-MS reveals the presence of volatile and toxic compounds

The analysis of electronic cigarrete (E-cigarette) fluids by high performance liquid chromatography or gas chromatography (GC) coupled to mass spectrometry (MS), GC hyphenated to flame-ionisation detection, or nuclear magnetic resonance spectroscopy poses many challenges due to the complex matrix and extremely high number of compounds present. In order to overcome these challenges, this study focused on the detection of the multiple complex compounds classes produced by the pyrolysis of E-cigarette liquids using comprehensive two dimensional gas chromatography (GCxGC) coupled to time of flight (TOF)-MS. Gas samples were prepared by heating E-liquids inside aluminium tins for 5 min. The tins were placed in a sand bath, which was temperature controlled at 200 °C. The samples were collected using thermal desorption tubes connected to volatile organic compound (VOC) sampling pump attached and subsequently analysed using GCxGC-TOF-MS. The greater peak resolution obtained when using GCxGC-TOF-MS allowed to distinguish many toxic compounds and VOCs that could not be detected by the other methods mentioned above. As a result, a comprehensive list of volatile compounds emitted from E-cigarette fluids when heated was established, which might allow a better understanding of potential health effects of vaping. Heating E-liquids to moderate temperature results in the emission of over 1000 volatile compounds of which over 150 are toxic. These compounds are either present in the liquid or can be formed during storage or heating leading to a more complex volatile profile of E-cigarette liquids than previously assumed. The application of GCxGC-TOF-MS allows the elucidation of this profile and therefore a better understanding of possible health implications.