Ratio of Propylene Glycol to Glycerol in E-Cigarette Reservoirs Is Unchanged by Vaping as Determined by 1h NMR Spectroscopy.

The passage discusses the composition of e-cigarette aerosols and how it can impact the exposure and deposition of various compounds in the respiratory tract, particularly propylene glycol (PG) and glycerol (GL), and their thermal degradation products. The thermal degradation products, including formaldehyde, acetaldehyde, and acrolein, are volatile and primarily exist in the gas phase, while PG and GL have different boiling points, leading to varying distributions between the gas and particulate phases of the aerosol. The distribution of these compounds in the aerosol can be influenced by various factors, such as the device, settings, and e-liquid composition. The aerosol can contain a higher concentration of PG in the gas phase due to its semi-volatile nature, while GL is primarily found in the particulate matter. The majority of the gas-phase mass is comprised of volatile and semi-volatile molecules, including substantial PG, while most of the GL is in the particulate matter. The GL fraction in the reservoir grows during aerosolization, and the effects of various e-cigarette settings and e-liquid compositions offer insight into the unique health effects associated with different e-cigarette exposures. The amount and type of thermal degradation products can vary depending on puff duration, wattage, temperature, coil type, and the presence of flavorants. E-cigarettes can aerosolize e-liquids at non-equilibrium conditions, and the original e-liquid composition in the tank may not change notably during or after aerosolization.

Kerber PJ, Duell aK, Peyton Dh. Ratio of Propylene Glycol to Glycerol in E-Cigarette Reservoirs Is Unchanged by Vaping as Determined by 1h NMR Spectroscopy. Chemical research in toxicology. 2021;34(8):1846-1849. doi:10.1021/acs.chemrestox.1c00208