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Tobacco products generally contain tobacco-derived nicotine (TDN; having ∼99+% ( S )-(-)-nicotine). Recent United States regulation has led some producers to transition to synthetic ("tobacco-free") nicotine. For example, Puff Bar is now marketed with tobacco-free nicotine (TFN; presumed to be racemic). To evaluate the claim that these new products contain TFN, we evaluated the presence of the two nicotine optical isomers by 1 H NMR spectroscopy, polarimetry, and gas chromatography-mass spectrometry. Older Puff Bars were found to contain ( S )-(-)-nicotine, and newer "TFN" Puff Bars were found to contain both ( R )-(+) and ( S )-(-) isomers-indicating TFN, albeit with slightly more of the ( S )-(-)-nicotine form.

Introduction: The distribution of nicotine among its free-base (fb) and protonated forms in aerosolised nicotine affects inhalability. It has been manipulated in tobacco smoke and now in electronic cigarettes by the use of acids to de-freebase nicotine and form 'nicotine salts'., Methods: Measurements on electronic cigarette fluids (e-liquids) were carried out to determine (1) the fraction of nicotine in the free-base form ( α fb ) and (2) the levels of organic acid(s) and nicotine. Samples included JUUL 'pods', 'look-a-like/knock-off' pods and some bottled 'nicotine salt' and 'non-salt' e-liquids., Results: α fb = 0.12 ±0.01 at 40°C (≈ 37°C) for 10 JUUL products, which contain benzoic acid; nicotine protonation is extensive but incomplete., Discussion: First-generation e-liquids have α fb ≈ 1. At cigarette-like total nicotine concentration (Nic tot ) values of ~60 mg/mL, e-liquid aerosol droplets with α fb ≈ 1 are harsh upon inhalation. The design evolution for e-liquids has paralleled that for smoked tobacco, giving a 'déjà vu' trajectory for α fb . For 17th-century 'air-cured' tobacco, α fb in the smoke particles was likely ≥ 0.5. The product α fb Nic tot in the smoke particles was high. 'Flue-curing' retains higher levels of leaf sugars, which are precursors for organic acids in tobacco smoke, resulting in α fb ≈ 0.02 and lowered harshness. Some tobacco cigarette formulations/designs have been adjusted to restore some nicotine sensory 'kick/impact' with α fb ≈ 0.1, as for Marlboro. Overall, for tobacco smoke, the de-freebasing trajectory was α fb ≥ 0.5 → ~0 →~0.1, as compared with α fb = ~1 →~0.1 for e-cigarettes. For JUUL, the result has been, perhaps, an optimised, flavoured nicotine delivery system. The design evolution for e-cigarettes has made them more effective as substitutes to get smokers off combustibles. However, this evolution has likely made e-cigarette products vastly more addictive for never-smokers., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Heat-not-burn products, eg, I quit ordinary smoking (IQOS), are becoming popular alternative tobacco products. The nicotine aerosol protonation state has addiction implications due to differences in absorption kinetics and harshness. Nicotine free-base fraction (α fb ) ranges from 0 to 1. Herein, we report α fb for IQOS aerosols by exchange-averaged 1 H NMR chemical shifts of the nicotine methyl protons in bulk aerosol and verified by headspace-solid phase microextraction-gas chromatography-mass spectrometry. The α fb ≈ 0 for products tested; likely a result of proton transfer from acetic acid and/or other additives in the largely aqueous aerosol. Others reported higher α fb for these products, however, their methods were subject to error due to solvent perturbation.