Levels of Selected Groups of Compounds in Refill Solutions for Electronic Cigarettes

Electronic cigarettes are gaining in popularity worldwide. However, information about chemical evaluations of refill solutions is very limited. Our study aimed to develop methods and to assess the levels of eight groups of compounds in 55 refill solutions for 17 brands. The eight chemical groups include mono/polyhydric alcohols, tobacco alkaloids, tobacco-specific nitrosamines (TSNAs), solanesol, phenolic compounds, carbonyl compounds, volatile organic compounds (VOCs), and polycyclic aromatic hydrocarbons (PAHs).

Selected compounds were extracted from refill solutions and analyzed with appropriate chromatographic and spectroscopic methods.

The total mass percentage of propylene glycol and glycerol in most refill solutions ranged from 80%~97%. Triethylene glycol was detected in one sample and menthol was found in 16 samples, including in samples that were not labeled as "mint". The labeled concentrations of nicotine of the 25 samples were not consistent with, and were in most cases lower than the measured concentrations. The concentrations of nicotine in samples that were labeled at the same "strength" (eg, HIGH, MIDDLE, or LOW) differed significantly among brands. Selected groups of compounds including TSNAs, solanesol, VOCs, PAHs, phenolic compounds, and carbonyl compounds were all detectable, with varying levels and detection frequencies.

A panel of methods were developed and validated and subsequently used to assess the levels of selected groups of compounds in electronic cigarette refill solutions. Propylene glycol and glycerol constituted the major ingredients of most refill solutions. The nicotine content was generally not labeled clearly or accurately. The exposure and health effects on consumers of these impurities, toxicants, or carcinogens should be further evaluated.

Our study have developed methods and assessed the levels of eight groups of compounds in 55 refill solutions for 17 brands in the Chinese market. Our study shows that propylene glycol and glycerol constitute the major ingredients of most refill solutions, and also indicated the necessity for clearly and accurately labeling nicotine content of e-liquids. Compounds that may originate from tobacco, solvents or other sources, such as TSNAs, solanesol, VOCs, PAHs, phenolic compounds, and carbonyl compounds were all found with different levels and detection frequencies.