Transfer of metals in the liquids of electronic cigarettes

Abstract

Objectives: E-cigarettes are electronic devices containing a liquid that usually consists of a mixture of glycerol, propylene glycol and nicotine, with or without flavorings, in various concentrations. A vapor or aerosol is produced, and inhaled from the user, when this liquid is heated by a heating coil. This work examines the impact of three parameters (e-liquid composition, nicotine content and air flow) on the transfer of metals' from the heating coils to the e-liquids.

Materials and methods: A distillation unit was used, where 20ml of an e-liquid were boiled with two commercial heating elements. Four e-liquids: 100% Propylene Glycol, 100% Glycerol, 50/50% Propylene Glycol/Glycerol, 33.3/33.3/33.3% Propylene Glycol/Glycerol/Water, three nicotine contents: 0, 0.4 and 0.8% per volume and three air flows: 0, 0.5 and 1.0 L/min, were used. The liquids were analyzed by Total Reflection X-Ray Fluorescence spectrometry to determine the final content of metals.

Results and discussion: Five metals, Fe, Ni, Cu, Zn, and Pb, were found to be transferred from the heating coils to the e-liquids. The transfer of those metals increases with air flow and nicotine concentration, while e-liquid composition also has a significant impact. Glycerol enhances the transfer of metals compared to propylene glycol and their mixtures. The boiling temperature of the e-liquids increases significantly the transfer of metals in the e-liquids.

Conclusions: There is a transfer of metals from the heating coils to the e-liquids. This transfer depends on the e-liquid composition and on the boiling temperature.

Keywords:

• Copper
• electronic cigarettes
• glycerol
• lead
• metals
• nickel
• propylene glycol
• zinc

Disclosure statement

The authors acknowledge having no financial interest or benefit arisen from the direct applications of this work.

Additional information

Funding

This work was supported by the Hellenic Thoracic Society (no Grant number).