Determination of amounts of harmful substances migrating from plastic assemblies in electronic cigarettes
Plastic materials are widely used in assemblies of e-cigarettes. Plastic materials shall not transfer harmful substances to the content of e-liquid in quantities which change the composition of the e-liquid or the aerosol and thereby increase the risk for consumers in accordance with the standards published by European, French and Bratish. Depending on the type of plastic materials used, the harmful substances were identified, including formaldehyde, terephthalic acid, isophthalic acid, phenol, bisphenol A, ethylene glycol, vinyl chloride, acrylonitrile, 1,3-butadiene, etc. According to the actual conditions of plastic assemblies’ contacting with e-liquid, aerosol and mouth, migration tests were established under storage and working conditions. Five analysis methods were developed for identifying those harmful substances in the following two simulants: a) the mixture of propylene glycol, glycerol, nicotine and water; b) water. The migration amounts of harmful substances from plastic assemblies in 30 e-cigarette samples were determined. The results indicated that: 1) ethylene glycol, terephthalic acid, isophthalic acid and vinyl chloride were not detected in any simulants; 2) the migration levels of bisphenol A, formaldehyde, phenol, acrylonitrile and 1,3-butadiene varied between 0.85~291.10, 6.92~52.11, 0.10~11.32, 2.12 and 0.16 mg/kg, respectively. Compared with the regulatory SMLs (specific migration limits) of those harmful substances set by the Commission Regulation (EU) No 10/2011, the migration levels of ethylene glycol, terephthalic acid, isophthalic acid, vinyl chloride, acrylonitrile and 1,3-butadiene were below the SMLs, which may not raise migration risk; however, the migration levels of bisphenol A, formaldehyde and phenol exceeded the SMLs, and the percentages of samples were 83.3%, 30.0% and 23.3%, which may raise migration risk.