Universal electronic-cigarette test: physiochemical characterization of reference e-liquid

Abstract

BackgroundDespite the rising health and safety concerns of e-cigarettes, a universal e-cigarette testing method is still in its early developmental stage. The aim of this study was to develop an e-liquid Reference Material that can be used to improve accuracy and reproducibility of research results, and advance health risk assessment of e-cigarette products.MethodsE-liquid Reference Material was developed by purity assessment, gravimetric measurement, homogeneity testing, and stability testing with material and instrument traceability (adopted from ISO 35:2006E).ResultsHomogeneity tests showed e-liquid Reference Material requires ≥ 1 h rotation at a speed of 5 rpm to reach complete homogeneity. Stability tests showed homogeneity is intact for at least 2 weeks without secondary separation, and e-liquids are stable in 21 °C–50 °C thermocycling conditions up to 72 h. A change in the e-liquid color was first observed at day seven, and progressed to 2- and 16 - fold increase in absorbance by one and 6 months respectively. We found that e-liquids do not have inherent material instabilities such as immiscibility or secondary separation. However, discrepancies in concentration and composition arose mainly due to viscosity of propylene glycol and glycerin. Aerosol generated from the e-liquid Reference Material had 16 chemical-byproducts and was composed of ~634,000 particles of which 38% were Fine Particulate Matters (<0.5 μm in diameter).ConclusionsThe efforts described here to create a standardized e-liquid Reference Material aim to provide unbiased and robust testing parameters that may be useful for researchers, the industry and government agencies. Additionally, the reference e-liquid could open a channel of conversation among different laboratories by providing the means of independent verification and validation while establishing a system of transparency and reproducibility in materials and methods.

Cariogenic potential of sweet flavors in electronic-cigarette liquids

“…Aerosols were generated by using a Universal Electronic-Cigarette Testing Machine (UECTM) developed by the American Dental Association (ADA) Foundation in collaboration with the University of Maryland, Department of Chemistry [ 26 ]. For all experiments, a commercial sub-ohm tank (Aspire Cleito: 0.2 Ω Kanthal coil with cotton wick) was used.…”

“…Flavor-free reference e-liquid was prepared following our previous work (20/80 propylene glycol/glycerin (by volume fraction) with 10 mg/mL nicotine) [ 26 ]. To increase reproducibility, gravimetric method was used (0.410 g propylene glycol, 2.000 g glycerin and 20.0 mg nicotine) [ 26 ].…”

“…The U.S. Food and Drug Administration (FDA)’s Center for Tobacco Products (CTP) issued an Advance Notice of Proposed Rulemaking (ANPRM) to obtain information related to the role that flavors play in tobacco products (Docket Number: FDA-2017-N-6565). However, internationally recognized standards (e.g., The International Organization for Standardization) on manufacturing and safety testing methods are still in an early developmental stage [ 26 ].…”

“…Sucrose or sucralose is added for the sweet taste in e-liquids and sugar alcohol (e.g., ethyl maltol) is used for the sweet fragrance [ 27 – 29 ]. In a previous study, it was shown that the viscous base is a major cause of unintended compositional error during manufacturing and bottling processes [ 26 ]. E-liquids, especially those made from glycerin (1.412 Pa•s) have high viscosity properties.…”

Use of Electronic Cigarettes in European Populations: A Narrative Review

“…These different types of electronic nicotine delivery systems are designed to be either less harmful than regular cigarettes or used as nicotine replacement therapy (NRT) [1]. The electronic nicotine device generally consists of a power source, usually a battery, and a heating element that creates an aerosol that is inhaled by the user after the e-liquid (the solution inside a device) has been heated to a temperature of above 350 • C [2,3].…”