title: Free-Base and Protonated Nicotine in Electronic Cigarette Liquids and Aerosols.
abstract: As with other tobacco aerosols, nicotine delivery from e-cigarettes (ECIG) depends on the total nicotine and its partitioning between free-base (Nic) and protonated (NicH(+)) forms. Previous studies of ECIG nicotine emissions have generally reported "nicotine yield" without attention to whether the methods employed resulted in quantification of the total nicotine or only one of its forms, making reported results difficult to compare across studies or to evaluate against reported blood exposure. This study reports a convenient solvent extraction method for determining total nicotine and its partitioning in ECIG liquids and aerosols by gas chromatography. Commercial ECIG liquids and aerosols were analyzed, and it was found that most of the nicotine was in the Nic form, with aerosols exhibiting higher Nic fraction than the parent liquids. Apparent pH was found to correlate with nicotine partitioning and can provide a useful indirect measure when chromatography is unavailable. Finally, labeled ECIG liquid nicotine concentration in commercial products was often inconsistent with measured nicotine.
authors.affiliation: §Center for the Study of Tobacco Products, Virginia Commonwealth University, 821 West Franklin Street, Richmond, Virginia 23284, United States.
authors.forename: Ahmad
authors.initials: A
authors.lastname: El-Hellani
authors.affiliation: §Center for the Study of Tobacco Products, Virginia Commonwealth University, 821 West Franklin Street, Richmond, Virginia 23284, United States.
authors.forename: Rachel
authors.initials: R
authors.lastname: El-Hage
authors.affiliation: §Center for the Study of Tobacco Products, Virginia Commonwealth University, 821 West Franklin Street, Richmond, Virginia 23284, United States.
authors.forename: Rima
authors.initials: R
authors.lastname: Baalbaki
authors.affiliation: §Center for the Study of Tobacco Products, Virginia Commonwealth University, 821 West Franklin Street, Richmond, Virginia 23284, United States.
authors.forename: Rola
authors.initials: R
authors.lastname: Salman
authors.affiliation: §Center for the Study of Tobacco Products, Virginia Commonwealth University, 821 West Franklin Street, Richmond, Virginia 23284, United States.
authors.forename: Soha
authors.initials: S
authors.lastname: Talih
authors.affiliation: §Center for the Study of Tobacco Products, Virginia Commonwealth University, 821 West Franklin Street, Richmond, Virginia 23284, United States.
authors.forename: Alan
authors.initials: A
authors.lastname: Shihadeh
authors.affiliation: §Center for the Study of Tobacco Products, Virginia Commonwealth University, 821 West Franklin Street, Richmond, Virginia 23284, United States.
authors.forename: Najat A
authors.initials: NA
authors.lastname: Saliba
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D002623:Chemistry Techniques, Analytical; D066300:Electronic Nicotine Delivery Systems; D006863:Hydrogen-Ion Concentration; D009538:Nicotine / Q000032:analysis*; D011522:Protons; D012997:Solvents / Q000737:chemistry
chemical_list: D000336:Aerosols; D011522:Protons; D012997:Solvents; D009538:Nicotine