We assumed that meaningful conclusions could be obtained by analysing 30 products. The e-cigarette fluids examined were selected from a vast and rapidly changing array of products. BLU and NJOY, two brands of disposable-cartridge e-cigarettes, were purchased in five flavours: tobacco, menthol, vanilla, cherry and coffee. Also purchased in the same flavours (from online retailers and local ‘vape’ shops in Portland, Oregon) were refill bottles for tank systems. Refill bottles in five other confectionary flavours (chocolate/cocoa, grape, apple, cotton candy and bubble gum) were also purchased. After dilution with methanol, the fluids were analysed by GC/MS. Using internal standard-based calibration procedures similar to those described elsewhere,16 (link) analyses were performed using an Agilent (Santa Clara, California, USA) 7693 autosampler, Agilent 7890A GC and Agilent 5975C MS. The GC column type was Agilent DB-5MS UI, of 30 m length, 0.25 mm id and 0.25 mm film thickness. For each replicate sample, ∼50 mg of each fluid was dissolved in 1 mL of methanol. One microlitre of the methanol solution was then injected on the GC with a 25:1 split. The GC temperature programme for all analyses was: 35°C hold for 5 min; 10°C/min to 300°C; then hold for 3.5 min at 300°C. No analyses of aerosols generated from the fluids were carried out.
Qualitative analyses of the 30 e-cigarette fluids were first carried out here using the NIST 14 MS library,17 and the results were compared with data previously obtained for flavoured tobacco products.16 (link) Quantitative analyses of the 30 fluids were then undertaken, using authentic standards, for a specific list of compounds, which formed the ‘target analyte list’. If reported here, the presence of each target analyte was confirmed by matching GC retention times and MS patterns with results obtained with the authentic standards; the level was determined by comparison with calibration standard runs. The target analyte list included the 70 compounds listed in Brown et al16 (link) plus 20 others, namely aromadendrene, 1,4-cineol, trans-cinnamaldehyde, citronellal, citronellyl propionate, coumarin, decanal, ethyl acetate, ethyl hexanoate, fenchol, limonene oxide, trans-linalyl propionate, maltol, 3′-methylacetophenone, neomenthol, 2-nonanone, pentyl propionate, pulegone, γ-terpineol and 2,3,5,6-tetramethylpyrazine. The vicinal diketone compounds diacetyl and 2,3-pentanedione were not in the target analyte list.
Qualitative analyses of the 30 e-cigarette fluids were first carried out here using the NIST 14 MS library,17 and the results were compared with data previously obtained for flavoured tobacco products.16 (link) Quantitative analyses of the 30 fluids were then undertaken, using authentic standards, for a specific list of compounds, which formed the ‘target analyte list’. If reported here, the presence of each target analyte was confirmed by matching GC retention times and MS patterns with results obtained with the authentic standards; the level was determined by comparison with calibration standard runs. The target analyte list included the 70 compounds listed in Brown et al16 (link) plus 20 others, namely aromadendrene, 1,4-cineol, trans-cinnamaldehyde, citronellal, citronellyl propionate, coumarin, decanal, ethyl acetate, ethyl hexanoate, fenchol, limonene oxide, trans-linalyl propionate, maltol, 3′-methylacetophenone, neomenthol, 2-nonanone, pentyl propionate, pulegone, γ-terpineol and 2,3,5,6-tetramethylpyrazine. The vicinal diketone compounds diacetyl and 2,3-pentanedione were not in the target analyte list.