An Analytical Perspective on Determination of Free Base Nicotine in E-Liquids. (10th March 2020)

• Record Type: Journal Article
• Authors: Gholap, Vinit V.; Heyder, Rodrigo S.; Kosmider, Leon; Halquist, Matthew S.
• Other Names: Milea Demetrio Academic Editor.
• Is Part Of: Journal of analytical methods in chemistry. Volume 2020(2020)
• Publication Date: 2020-03-10
• Subjects: Chemistry, Analytic -- Periodicals; Chemistry, Analytic -- Technique -- Periodicals; 543.05
• DOI: 10.1155/2020/6178570
• Languages: English
• ISSNs: 2090-8865

Abstract

Abstract : In electronic cigarette users, nicotine delivery to lungs depends on various factors. One of the important factors is e-liquid nicotine concentration. Nicotine concentration in e-liquids ranges from 0 to >50 mg/mL. Furthermore, nicotine exists in protonated and unprotonated ("free base") forms. The two forms are believed to affect the nicotine absorption in body. Therefore, in addition to total nicotine concentration, e-liquids should be characterized for their free base nicotine yield. Two approaches are being used for the determination of free base nicotine in e-liquids. The first is applying a dilution to e-liquids followed by two methods: Henderson–Hasselbalch theory application or a Liquid-Liquid Extraction. The second is the without-dilution approach followed by 1 H NMR method. Here, we carried out controlled experiments using five e-liquids of different flavors using these two approaches. In the dilution approach, the Henderson–Hasselbalch method was tested using potentiometric titration. The accuracy was found to be >98% for all five e-liquid samples ( n = 3). A Liquid-Liquid Extraction was carried out using toluene or hexane as extraction solvent. The Liquid-Liquid Extraction technique was found to be limited by solvent interactions with flavors. Solvent extractions resulted in flavor dependent inaccuracies in free base nicotine determination (5 to 277% of calculated values). The without-dilution approach was carried out using 1 H NMR as described by Duell et al. This approach is proposed to offer an independent and alternative scale. None of the methods have established a strong correlation between pre- and postvaporization free base nicotine yield. Here we present comparative results of two approaches using analytical techniques. Such a comparison would be helpful in establishing a standardized method for free base nicotine determination of e-liquids.