The chemical components of electronic cigarette cartridges and refill fluids: review of analytical methods

To date, several concerns have been raised on the purity of ingredients employed in the manufacturing processes of refill fluids and cartridges, the device functionality, and the quality control of electronic cigarettes. This article reviews analytical methods so far described for the analysis of liquids to detect their chemical components and to investigate the presence of toxicants and carcinogens that can potentially occur as impurities of ingredients or as a consequence of their degradation.

Based on the scientific literature, high-performance liquid chromatography with diode-array detection (HPLC/DAD) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) are most appropriate for determining nicotine and related compounds in fluids and cartridges, whereas LC-MS/MS has been successfully used to determine nitrosamines. Content analyses of glycols have been performed using gas chromatography equipped with flame ionization detector or gas chromatography/mass spectrometry (GC/MS), whereas carbonyl and other volatile organic compounds determinations have been performed by HPLC/DAD and GC/MS, respectively. Content analyses of heavy metals have been performed by inductively coupled plasma optical emission spectroscopy or inductively coupled plasma mass spectrometry. Since new potentially toxic substances may be created during heating, it is also necessary to investigate the chemical composition of generated aerosol. In this case, similar methods applied for tobacco smoke can be adopted.

A broad range of analytical techniques are available for the detection of constituents and toxicants in e-liquids and cartridges. Analyses of liquids have been performed with pharmacopeia procedures and methods (International Organization for Standardization, Environmental Protection Agency, and American Public Health Association) developed for other matrices but applicable to e-liquids. Because new potentially harmful substances may be produced during heating process, analyses of aerosol are needed to correlate its composition to the chemical components of liquids.