The objective of this study was to develop and validate an analytical method for determining nicotine, and nicotine related compounds (i.e. nicotine-N-oxide, cotinine, nornicotine, anatabine, myosmine, anabasine, and ß-nicotyrine) in e-cigarette aerosols and e-liquids.

Aerosol collection was achieved using a Cambridge collection pad. The sample preparation consisted of adding deuterated internal standards to the collection pad and extracting with 100 mM ammonium acetate solution using a wrist action shaker. The filtrate was then analyzed by LC-MS/MS using a Gemini NX C18 column (3 um, 150x3 mm) with a mobile phase gradient system consisting of acetonitrile and 10% acetonitrile in 10 mM ammonium bicarbonate (pH=8.0) and electrospray ionization (ESI) in the positive mode. The e-liquid was analyzed using the same instrumental parameters, but simplifying the sample preparation procedure by adding deuterated internal standards to the 100 mg sample and the sample was then extracted with 100 mM ammonium acetate solution, sonicated, and filtrated.

In this study, the method’s accuracy, robustness, and reliability were enhanced by using deuterated analogues of each analyte as internal standard and by applying two ion-transition pairs for each analyte for the confirmation and quantification. Validation experiments demonstrated good sensitivity, specificity and reproducibility. All target analyte curves exhibited good linearity from 50 to 5000 ng/ml (r² > 0.995). The average recoveries for e-liquids varied from 85.2% (nicotine-N-oxide) to 110% (ß-nicotyrine) with all CV < 5.0%. Similarly, the average recoveries for e-cig aerosols varied from 87.8% (for nicotine-N-oxide) to 111% (for myosmine) with all CV < 8.8%. The LOD and LOQ for e-liquids for all target analytes ranged from 0.234 and 0.781 µg/g (cotinine) to 1.66 and 5.48 µg/g (nicotine-N-oxide). For e-cig aerosols these ranged from 0.094 and 0.312 µg/collection (cotinine) to 0.872 and 2.87 µg/collection (nicotine-N-oxide).