. All four vendors’ e-cigarette liquids appeared to contain ethanol, propylene glycol, glycerin, and nicotine. It is important to note that all four vendors listed propylene glycol, glycerin, and nicotine; however, none of the vendors listed ethanol as an ingredient. Blank analyses indicated that ethanol was not from laboratory contamination. Methylene chloride was used as the diluent to solve viscosity and concentrations issues, hence the abundant presence of methylene chloride. As shown in Figure 5, the rapid GC-FID method produced an acceptable external calibration of nicotine from 0.016 to 1.00 mg/mL (r > 0.995).