E-cigarettes have become a popular alternative to combustible cigarettes (CCs) in recent years. E-cigarette liquids (e-liquids) are marketed with different flavourings, from tobacco and common fruit flavours to “exotic” kinds like “magic stardust”. This implies the use of a broad range of aroma chemicals, and one flavour may consist of several compounds. Although the majority of flavours used are “generally recognised as safe” (GRAS) food additives, little is known about their potential harm after inhalation. Diacetyl (DA), acetoin (AC), and 2,3-pentanedione (PD) are approved for ingestion and commonly used as food additives to give a butter-like aroma, but also frequently present in e-liquids. However, they have shown adverse health effects when inhaled and therefore, the National Institute on Occupational Safety and Hazards (NIOSH) has proposed exposure limits for DA and PD (NIOSH limits).

This prompted us to develop a method for the simultaneous quantification of DA, AC, and PD based on gas chromatography coupled to mass spectrometry with negative chemical ionisation (NCI-GC-MS) after derivatisation and liquid-liquid extraction.

A lower limit of quantification (LLOQ) of 0.013 µg/g liquid was obtained for all three analytes. Initially, a small set of 26 e-liquids was investigated yielding concentrations above LLOQ for 96% (DA), 73% (AC), and 35% (PD) of the analysed e-liquids proving the suitability of the method for the intended purpose. Assuming a daily e-liquid intake of 3 ml, levels above the NIOSH exposure limit for DA (65 µg/d) were observed for two e-liquids. In contrast, all e-liquids were within the NIOSH limit for PD of 137 µg/d.

The study will be extended to a larger set of e-liquids and to aerosol. Current findings and an interpretation related to potential respiratory effects will be discussed in this presentation.