Determination of nicotine, glycerol, propylene glycol and water in electronic cigarette fluids using quantitative ¹ H NMR

Abstract

The variability of the electronic cigarette liquids (e-liquid) composition has the potential to influence not only the amount of nicotine delivered to the user, but also the type and amount of generated byproducts and subsequent health risks. For this reason, it is important to characterize all of the chemical components of e-liquids. We report the development and application of a single 1H NMR analysis method to identify and quantify the most abundant chemical components (nicotine, glycerol, 1,2-propylene glycol, and water) likely to be present as their influence on the composition of inhaled vapor is not know. For 1H NMR, the solvent has to dissolve the e-liquids at a concentration sufficient to readily determine the concentration of nicotine present, and the solvent and internal standard cannot possess exchangeable protons which would interfere with determining the concentrations of the analytes of interest. To fulfill these requirements, perdeuterated N,N-dimethylformamide (DMF-d7) was selected as the solvent, with 1,2,4,5-tetrachloro-3-nitrobenzene as the internal standard. Nicotine concentrations from 58 different e-liquids obtained using 1H NMR were found to agree with the results from GC-MS analysis. Generally, the amount of nicotine present was close to that claimed by the manufacturer. In some cases, the proportions of 1,2-propylene glycol, glycerol, and water varied significantly between flavors within a brand and within flavors depending on the nicotine content. In one case, 1,2-propylene glycol was identified where the manufacturer had stated none should be present.

Role of sweet and other flavours in liking and disliking of electronic cigarettes

“…According to the manufacturer, these flavours contained a 60:40 ratio of vegetable glycerin (VG):propylene glycol. Although we did not experimentally confirm this ratio, in a now-discontinued version of these blu eCig flavours (purchased in January 2014), we previously found no VG in the e-liquid 17. All blu Tanks flavour cartridges used in this study were purchased online through the blu eCig website in August 2015, and the tanks were coupled with the blu PLUS+ battery system.…”

Aerosol size distribution measurement of electronic cigarette emissions using combined differential mobility and inertial impaction methods: Smoking machine and puff topography influence

“…PG has higher volatility than VG and therefore a higher content of PG should lead to higher evaporative losses. In our earlier study (Mikheev et al 2016) blu e-cigs that were used had e-liquids based on VG (Crenshaw et al 2016) whereas blu e-cigs used for the current study in general had comparable PG and VG amounts (therefore higher evaporative losses are expected).…”

“…E-liquid analysis for the major component (PG, VG, nicotine, and water) of blu e-cigs was conducted using the proton nuclear magnetic resonance (HNMR) method described elsewhere (Crenshaw et al 2016). E-liquid was extracted from the cartridges by 15 min of centrifuging at 3,000 revolutions per minute ($1-2 mL/ cartridge).…”

A review of nicotine‐containing electronic cigarettes—Trends in use, effects, contents, labelling accuracy and detection methods

“…One study, however, that used toluene to extract the nicotine from the e‐liquid to remove any possible interferences from the sample being injected onto the GC had a 92.1% recovery 33 . Many of the GC‐MS studies described the use of internal standards to aid in the quantification of nicotine which included nicotine‐ d3 , 38 nicotinium‐ d3 , 13 naphthalene‐ d8 , 39 hexadecane, 33 n‐heptadecane, 27 and caffeine 41 . For GC‐based techniques not involving mass spectrometry, quinoline 35,75 and quinolone 36,37 have been employed as well as n‐heptadecane 46 …”