Kinetics of aldehyde Flavorant-acetal Formation in E-Liquids with Different E-Cigarette Solvents and Common additives Studied by 1h NMR Spectroscopy.

Introduction:
This article reports on a study examining the formation of acetals, a type of chemical compound, from flavoring agents in electronic cigarettes (e-cigarettes) using propylene glycol (PG) as a solvent. The study aimed to understand the impact of acetal formation on indoor partitioning and thirdhand exposure, or the potential for residual chemicals from e-cigarette use to accumulate on surfaces and be absorbed through skin or inhalation.

Key Points:

* The study used 1h NMR spectroscopy to determine the rate and yield of aldehyde flavorant-acetal formation in PG e-liquids and then PG e-liquids with water, nicotine, benzoic acid, and mixtures of nicotine+benzoic acid.
* acetalization occurred at a faster rate and produced a higher yield in e-liquids with GL compared to PG.
* acetal formation in PG e-liquids with flavorants was inhibited by nicotine and water (i.e., a base and an acetalization product, respectively) and catalyzed by benzoic acid.
* PG e-liquids containing nicotine and flavorants with 2, 4, and 10 times more benzoic acid than nicotine (by mol) generally formed acetals at a slower rate compared to e-liquids without nicotine and benzoic acid.
* Flavorant acetals have unique toxicity profiles and can be more harmful than the parent flavorant.
* The rate and yield of additional flavorant-acetal and -ketal formation in e-liquids with and without common additives and the impact on other reactions should also be explored to inform consumers and regulators about the hPhCs in e-liquids before and after aerosolization.

Main Message:
The study highlights the importance of considering the chemical reactions that occur in e-cigarette liquids, as they can impact the formation of potentially harmful compounds. The findings suggest that the presence of nicotine and the use of certain additives can influence the rate of acetal formation, which has implications for indoor air quality and potential thirdhand exposure. The study also emphasizes the need for further research to better understand the potential health impacts of these chemical reactions and to inform regulatory efforts.

Kerber PJ, Peyton Dh. Kinetics of aldehyde Flavorant-acetal Formation in E-Liquids with Different E-Cigarette Solvents and Common additives Studied by 1h NMR Spectroscopy. Chemical research in toxicology. 2022;35(8):1410-1417. doi:10.1021/acs.chemrestox.2c00159