利用低分辨率台式核磁共振波谱法测定电子烟液中的尼古丁质子化状态。
Determination of Nicotine Protonation State in E-Liquids by Low-Resolution Benchtop NMR Spectroscopy.
机构信息
Centre for Health Protection, National Institute for Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9, 3721 MA Bilthoven, The Netherlands.
出版信息
Chem Res Toxicol. 2024 Aug 19;37(8):1283-1289. doi: 10.1021/acs.chemrestox.3c00417. Epub 2024 Jul 25.
Over several years, e-liquids with "nicotine salts" have gained considerable popularity. These e-liquids have a low pH, at which nicotine occurs mostly in its monoprotonated form. Manufacturers usually accomplish this by the addition of an organic acid, such as levulinic acid, benzoic acid, or lactic acid. Nicotine in its protonated form can be more easily inhaled, enhancing the addictiveness and attractiveness of products. Several techniques have been described for measuring the protonation state of nicotine in e-liquids. However, nuclear magnetic resonance (NMR) spectroscopy is particularly suited for this purpose because it can be performed on unaltered e-liquids. In this article, we demonstrate the suitability of a benchtop NMR (60 MHz) instrument for determining the protonation state of nicotine in e-liquids. The method is subsequently applied to measure the protonation state of 33 commercially available e-liquids and to investigate whether the vaping process alters the protonation state of nicotine. For this purpose, the protonation state in the condensed aerosol obtained by automated vaping of different e-liquids was compared with that of the original e-liquids. Two distinct populations were observed in the protonation state of nicotine in commercial e-liquids: free-base (fraction of free-base nicotine α > 0.80) and protonated (α < 0.40). For 30 e-liquids out of 33, the information on the packaging regarding the presence of nicotine salt was in agreement with the observed protonation state. Three e-liquids contained nicotine salt, even though this was not stated on the packaging. Measuring the protonation state of nicotine before and after (machine) vaping revealed that the protonation state of e-liquids is not affected by vaping. In conclusion, it is possible to determine the nicotine protonation state with the described method. Two clusters can be distinguished in the protonation state of commercial e-liquids, and the protonation state of nicotine remains unchanged after vaping.
几年来，含有"尼古丁盐"的电子烟液已经变得非常流行。这些电子烟液的 pH 值较低，尼古丁在此条件下主要以单质子化形式存在。制造商通常通过添加有机酸（如乙酰丙酸、苯甲酸或乳酸）来实现这一点。质子化形式的尼古丁更容易被吸入，从而增强产品的成瘾性和吸引力。已经描述了几种技术来测量电子烟液中尼古丁的质子化状态。然而，核磁共振（NMR）光谱特别适合于这一目的，因为它可以在未改变的电子烟液上进行。在本文中，我们展示了台式 NMR（60 MHz）仪器用于确定电子烟液中尼古丁质子化状态的适用性。该方法随后用于测量 33 种市售电子烟液的质子化状态，并研究蒸汽过程是否会改变尼古丁的质子化状态。为此，通过自动蒸汽不同电子烟液获得的冷凝气溶胶中的质子化状态与原始电子烟液中的质子化状态进行了比较。在商业电子烟液中，观察到尼古丁的质子化状态存在两个明显的群体：游离碱（游离碱尼古丁的分数α>0.80）和质子化（α<0.40）。在 33 种电子烟液中有 30 种，包装上关于是否存在尼古丁盐的信息与观察到的质子化状态一致。有 3 种电子烟液含有尼古丁盐，尽管包装上没有说明。在蒸汽前后测量尼古丁的质子化状态表明，蒸汽过程不会影响电子烟液的质子化状态。总之，使用描述的方法可以确定尼古丁的质子化状态。商业电子烟液的质子化状态可以分为两个簇，蒸汽后尼古丁的质子化状态保持不变。
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