Fraction of Free-Base Nicotine in Simulated Vaping aerosol Particles Determined by X-ray Spectroscopies.

Introduction:
This article reports a study that investigates the acid-base equilibria of nicotine in hydrated vaping aerosols using X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXaFS) spectroscopy. The study aims to understand the impact of acidification on the chemical speciation of vaping aerosols, which is crucial for assessing the health effects of electronic cigarettes.

Key Points:

* The study used XPS and NEXaFS spectroscopy to probe the acid-base equilibria of nicotine in hydrated vaping aerosols.
* The authors found that nicotine in the core of aqueous particles was partially protonated when the ph of the nebulized solution was 10.4, with a fraction of free-base nicotine (αFB) of 0.34.
* Nicotine was further protonated by acidification with equimolar addition of benzoic acid (Ba), with αFB=0.17 at ph 6.2.
* The degree of nicotine protonation at the particle surface is significantly lower, with 0.72<αFB<0.80 in the same ph range.
* The presence of propylene glycol (PG) and glycerol (VG) completely eliminated protonation of nicotine at the surface (αFB=1) while not affecting its acid-base equilibrium in the particle core.
* The study also found that the addition of Ba to e-liquids can increase the aerosol's harshness, which may facilitate higher nicotine intake and promote addiction.
* The results provide insights into the role of acidifying additives in vaping aerosols, supporting public health policy interventions.

Main Message:
This study highlights the importance of understanding the chemical speciation of vaping aerosols, particularly the acid-base equilibria of nicotine. The findings demonstrate that acidification of vaping aerosols can increase nicotine protonation, which may have implications for nicotine delivery and health effects. The study also underscores the potential impact of acidifying additives in e-liquids on vaping behavior and addiction. These results support the need for further research and regulation of electronic cigarettes to ensure public health safety.

Weeraratna C, Tang X, Kostko O, et al. Fraction of Free-Base Nicotine in Simulated Vaping aerosol Particles Determined by X-ray Spectroscopies. The journal of physical chemistry letters. 2023;14(5):1279-1287. doi:10.1021/acs.jpclett.2c03748