Objectives Various organic acids are used to create nicotine salt formulations, which may improve the appeal and sensory experience of vaping electronic cigarettes (e-cigarettes). This clinical experiment examined the effects of partially and highly protonated forms of two nicotine salt formulations (nicotine lactate and benzoate) versus free-base (no acid additive) on the appeal and sensory attributes of e-cigarettes.

Methods Current adult tobacco product users (n=116) participated in an online remote double-blind within-subject randomised experiment involving standardised self-administration of e-cigarette solutions varying in nicotine formulation (free-base, 50% nicotine lactate –1:2 lactic acid to nicotine molar ratio, 100% nicotine lactate – 1:1 ratio, 50% nicotine benzoate and 100% nicotine benzoate). Each formulation had equivalent nicotine concentrations (27.0–33.0 mg/mL) and was administered in four flavours in a pod-style device. After each administration, participants rated appeal (liking, disliking and willingness to use again) and sensory attributes (0–100 scale).

Results Compared with free-base nicotine, 50% and 100% nicotine lactate and benzoate yielded higher appeal, smoothness and sweetness and lower harshness and bitterness. Dose–response analyses found 100% vs 50% nicotine salt improved appeal, smoothness, bitterness and harshness for nicotine lactate and sweetness, smoothness and harshness for nicotine benzoate. Solutions with higher pH were associated with worse appeal and sensory attributes across nicotine formulations. Nicotine formulation effects did not differ by tobacco use status and flavours.

Conclusion Restricting benzoic acid or lactic acid additives or setting minimal pHs in e-cigarettes merits consideration in regulations designed to reduce vaping among populations deterred from using e-cigarettes with aversive sensory properties.

Trial registration number This study was registered under ClinicalTrials.gov Identifier: NCT03742817 under the title ‘Effects of e-Cigarettes on Perceptions and Behavior’.