Free-Base andProtonated Nicotine in Electronic CigaretteLiquids and Aerosols.

Aswith other tobacco aerosols, nicotine delivery from e-cigarettes(ECIG) depends on the total nicotine and its partitioning betweenfree-base (Nic) and protonated (NicH+) forms. Previousstudies of ECIG nicotine emissions have generally reported “nicotineyield” without attention to whether the methods employed resultedin quantification of the total nicotine or only one of its forms,making reported results difficult to compare across studies or toevaluate against reported blood exposure. This study reports a convenientsolvent extraction method for determining total nicotine and its partitioningin ECIG liquids and aerosols by gas chromatography. Commercial ECIGliquids and aerosols were analyzed, and it was found that most ofthe nicotine was in the Nic form, with aerosols exhibiting higherNic fraction than the parent liquids. Apparent pH was found to correlatewith nicotine partitioning and can provide a useful indirect measurewhen chromatography is unavailable. Finally, labeled ECIG liquid nicotineconcentration in commercial products was often inconsistent with measurednicotine. [ABSTRACT FROM AUTHOR]