Within the last few years, e-cigarettes and other new smoking/vaping products have became more and more commonly used. Glycerol (VG) and propylene glycol (PG) are two important ingredients used in e-cigarettes and heat-not-burn (HnB) products either as principal components of e-liquids or as additives in HnB products. A wide range of pyrolysis products as well as thermal fragments of tobacco and tobacco ingredients could be determined with several analytical methods such as GC-MS or NMR. An on-line puff-by-puff analysis of thermal degradation products has the challenge to enable an analyte separation without pre-separation although the starting point of the thermal decomposition is a complex mixture and will provide multiple reaction pathways. Besides a fast sampling, a soft ionisation and an online data acquisition, mathematical methods, such as non-negative-matrix factorisation (NNMF), help to distinguish between different processes taking place during smoking/vaporisation and the respective analysis.

The measurements in this study were mainly performed using a modified Borgwaldt KC LM1 smoking machine coupled to a laser-photo-ionisation time-of-flight mass spectrometer. The modification of the smoking machine refers to 'cold-spot'-free sampling without affecting flow velocities and volumes. Our study was conducted with commercially available vaping as well as smoking products such as e-cigarettes, e-liquids and heat-not-burn products.

Pyrolysis products and thermal fragments such as carbonyls and other relevant classes of substances were investigated on a puff-by-puff basis. NNMF was used as a statistical tool to refer to the source of the detected analyte and to the specific reaction pathway. Especially for HnB products and flavoured e-liquids, analytes/substances besides VG and PG as well as their respective pyrolysis products were determined.

In summary, soft-photo-ionisation mass spectrometry was found to be as powerful for the investigation of emissions of new smoking/vaping products, such as e-cigarettes and HnB products, as it was already demonstrated for conventional combustible products.