Over the last few years, e-cigarettes and other innovative smoking/vaping products have become more and more commonly used. Whereas most manufacturers increase the safety and reliability of their products, there are consumers modifying devices in an unsafe way or directly misusing devices for generating an aerosol with an elevated level of drug. Soft photoionization (PI) of the aerosols released from those products provides an effective tool for investigating the chemical composition of the respective aerosols on a puff-by-puff resolved time basis. The most prominent unintended e-cigarette use-behaviour is the so called ‘dry burn’ or ‘dry puff’. This phenomenon occurs, when either the e-liquid reservoir is empty or the e-liquid cannot be transferred fast enough to the heated coil, especially, if the coil is not working temperature controlled. Consequently, a wide range of pyrolysis products could be released by the respective products. Applying online PI-mass spectrometry (MS) could potentially identify respective puffs and conditions, when the ‘dry burn’ appears. Besides the unintended e-cigarette use-behaviour caused by user modification or cheap, unsafe devices, PI-MS allows also to investigate intentional misuse of devices, e.g. for drug vaporization.

In general, there are two PI techniques that can be performed depending on the substance spectrum of interest: single-photon ionization (SPI@118nm), which ionizes a broad range of organic compounds, and resonance-enhanced multi-photon ionization (REMPI@266nm), which selectively ionizes aromatic compounds. Both techniques allow to effectively suppress analytical interferences originating from the smoke matrix, such as oxygen or nitrogen and even water vapour. Furthermore, mathematical/statistical methods such as non-negative-matrix-factorization can improve method performance whilst distinguishing between potential harmful compounds in the vapour/smoke of e-cigarettes as well as heat-not-burn products and measurement related artifacts.