The nicotine used in e-cigarette formulations is extracted from tobacco, and the purity of the nicotine can vary depending upon manufacturer and grade. The U.S. and European Pharmacopeias make recommendations for the purity of nicotine intended for pharmaceutical products; however, there is no official purity recommendation for the nicotine used in e-cigarettes. To date, there are only a few published reports on nicotine-related impurities in e-cigarette formulations. The objective of this work was to develop a sensitive, selective, and robust analytical method (LC-MS) for the quantitation of nicotine-related impurities (LC-MS) in e-vapor products and to evaluate these impurities in a variety of commercial e-cigarette cartridges and refill solutions (e-liquids). The nicotine-related impurities listed in the European Pharmacopeia guidelines were quantitatively investigated in 10 commercial e-cigarette cartridges and 10 refill solutions purchased from retail. For all products investigated, myosmine, anabasine, ß-nicotyrine, cotinine and nornicotine were well below 0.3% of the labelled nicotine concentrations. Anatabine levels exceeded 0.3% for 3 products and nicotine-N-oxide levels exceeded 0.3% in six products. In several cases, some nicotine related impurities increased with product age (as indicated by product sell-by-dates). The transfer efficiency of the nicotine-related impurities to the aerosol was also evaluated. Most of the nicotine-related impurities were observed to transfer to the aerosol. Nicotine-N-oxide showed low transfer efficiency and demonstrated significant thermal degradation. This selective and sensitive method is suitable to provide quantitative data for risk assessment analysis and for use in e-vapor product and refill solution stability studies as one of the stability indicating measures.