Untargeted chemical characterization of the aerosol generated by a heated tobacco product
In contrast to quantitative analysis, where chemical constituents of interest are targeted to the exclusion of all others, an untargeted approach considers indiscriminate determination of all analytes relevant to a specific chemical space. A portfolio of methods, based upon comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC×GC-TOFMS) and liquid chromatography with high-resolution accurate-mass spectrometry (LC-HRAM-MS) was applied for characterization of the aerosol generated by a heated tobacco product. The methods used were semi-quantitative in nature, and concentrations for a large number of compounds were estimated versus a limited number of stable isotope-labeled reference standards of known concentrations by using an internal standardization approach. A reporting threshold of 100 ng/item was applied, which served to optimize the proportion of substances identified relative to a practicable amount of effort required for their identification.
Applying the Health Canada Intense smoking regimen, a total of 529 chemical constituents (excluding water, glycerin, and nicotine) were identified to be present in the mainstream aerosol of the Tobacco Heating System (THS) 2.2, a heated tobacco product developed by Philip Morris Products S.A. and commercialized under the brand name IQOS®. The majority of constituents were present in the particulate phase (n = 402), representing more than 80 % of the total mass estimated by untargeted screening. The gas-vapour phase was represented by 166 constituents, with a proportion of these constituents being present in both particulate and gas-vapour phases (39 compounds). The identities of 80 % of all chemical constituents (representing > 96 % of the total determined mass) were confirmed by using authentic analytical reference materials.
All 529 constituents identified in THS 2.2 aerosol were also present in the mainstream smoke of the 3R4F reference cigarette.