Quantifying Nicotine in E-Cigarette Aerosols

To determine the amount of nicotine produced by the e-cigarette devices, five puffs of e-cigarette aerosols were collected on a glass fiber filter (MilliporeSigma, Burlington, MA, USA). Filters were then spiked with 40 μg of quinoline (98%, Sigma-Aldrich, Saint Louis, MO, USA) and extracted with 4 mL HPLC grade methanol (EMD Millipore, Billerica, MA, USA). quinoline was used as an internal standard due to its chemical similarity to nicotine, no interference in nicotine analysis, and its absence in the samples. Filter extracts were analyzed using the HPLC system described above (Waters 2690 equipped with a Polaris 3 column). External standards of nicotine (≥99%, Sigma-Aldrich, Saint Louis, MO, USA) and quinoline were prepared and quantified at 260 and 220 nm wavelengths, respectively. It should be noted that JUUL aerosols contain nicotine salts. Since these salts have a similar UV absorption maximum at 255–260 nm [35 (link)], they were quantified using the same nicotine standard. Details of nicotine analysis can be found in Tables S4 and S5.