Interconversion of nicotine enantiomers during heating and implications for smoke from combustible cigarettes, heated tobacco products, and electronic cigarettes.

Introduction:
This article presents a study on the interconversion of nicotine enantiomers during heating and its implications for smoke from combustible cigarettes, heated tobacco products, and electronic cigarettes. The study utilizes a Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS) method for the analysis of (S)- and (R)-nicotine.

Key Points:

* The LC-MS/MS method for the analysis of nicotine enantiomers was developed and applied to various samples, including nicotine from different sources, nicotine pyrolyzates, tobacco, smoke from combustible cigarettes and heated tobacco products, e-liquids, and particulate matter obtained from e-cigarettes aerosol.
* Nicotine starts decomposing upon heating above 450°C, leading to the formation of (R)-enantiomer from a sample of 99% (S)-nicotine and vice versa.
* The interconversion results in a slight increase in the content of (R)-nicotine in smoke compared with the level in tobacco for combustible cigarettes and heated tobacco products.
* The (S)/(R) ratio of nicotine enantiomers in e-liquids is identical to the ratio in the particulate phase of aerosols generated by e-cigarette vaping.
* a previous study on nicotine pyrolysis was found to be incorrect, as it did not consider that nicotine will evaporate at much lower temperatures in a pyrolyzer using a flow of gas.

Main Message:
The study highlights the importance of understanding the interconversion of nicotine enantiomers during heating and its implications for the composition of smoke from various tobacco products. The results suggest that nicotine enantiomer interconversion should be considered in the design and regulation of tobacco products, particularly in heated tobacco products and electronic cigarettes. additionally, the study emphasizes the need for accurate and reliable analytical methods for the determination of nicotine enantiomers in various matrices. Overall, the findings contribute to the ongoing efforts to understand the health effects of tobacco product use and inform regulatory decision-making.

Moldoveanu SC. Interconversion of nicotine enantiomers during heating and implications for smoke from combustible cigarettes, heated tobacco products, and electronic cigarettes. Chirality. 2022;34(4):667-677. doi:10.1002/chir.23421