The “quantity of nicotine exhaled” by an e-cigarette user is the most important factor influencing bystander exposure to nicotine. To that end, it is important to determine the quantity of nicotine that is retained by the e-cigarette user and not exhaled. Here we investigated the influence that vaping topography (i.e. mouth-hold versus inhaling) has upon the retention of nicotine following e-cigarette use in experienced volunteers.

Using a smoking machine, the mainstream aerosol from e-cigarettes containing different concentrations of nicotine were first evaluated by GC-FID to determine the relationship between quantity of nicotine delivered per puff and puff duration. The e-cigarettes were then freely vaped by volunteers through a cigarette holder attached to a smoking topography analyser which recorded puff volume and puff duration. This allowed the quantity of nicotine delivered to the volunteer during each puff to be determined. A Proton Transfer Reaction Mass Spectrometry (PTR-MS) machine, calibrated for nicotine, was then used to determine the quantity of nicotine exhaled following each use of the e-cigarettes and subtracting this figure from the estimated delivery enabled the retention rate to be calculated.

Our main finding was 98% the nicotine was retained by the volunteers when the e-cigarette aerosol was inhaled, regardless of puff volume or puff duration. In contrast, when the e-cigarette aerosol was held in the mouth only (i.e. no inhalation), a reduced but still a substantial quantity of nicotine, was retained. The novel experimental protocol presented here may also be used to determine the retention rates of other chemical components known to be present in e-cigarette aerosols.