title: On-Line Chemical Composition Analysis of Refillable Electronic Cigarette Aerosol-Measurement of Nicotine and Nicotyrine.
abstract: BACKGROUND
  Electronic cigarettes (e-cigs) generate aerosols that users inhale. Analyses of e-liquids inconsistently report nicotyrine, a nicotine analog that could impede nicotine metabolism, raising questions about nicotyrine formation.
  
  
  METHODS
  E-cig aerosols were analyzed on-line using a Thermal Desorption Aerosol Gas Chromatograph. Three e-liquids were tested: an unflavored solution in propylene glycol (PG); an unflavored solution in PG and vegetable glycerin (VG), and a flavored solution in PG and VG. A heating duration experiment determined the nicotyrine to nicotine ratio (NNR) in particle phase as a function of the duration of e-cig activation. An aging experiment determined the NNR in e-liquids and aerosols as a function of time since initial exposure to air and storage condition.
  
  
  RESULTS
  Nicotine and nicotyrine were quantified in all 3 e-liquids and aerosols. Duration of e-cig activation was inversely related to NNR (NNR = 0.04 with 3-s activation, 0.26 with 0.5 s). Aging influenced both e-liquid NNR and aerosol NNR. On average, the e-liquid NNR increased from 0.03 at 11 days after opening to 0.08 after 60 days. For similar heating durations, aerosol NNR increased from 0.05 at 11 days to 0.23 after 60 days. Storage conditions had little effect on NNR.
  
  
  CONCLUSIONS
  E-cig aerosols have variable nicotyrine quantities. Aerosol NNR depends on vaping technique and time elapsed since the e-liquid was exposed to air. It is hypothesized that aerosolized nicotyrine could facilitate nicotine absorption, inhibit the metabolism of nicotine, and reduce a user's urge to smoke.
authors.affiliation: School of Engineering and Applied Science, Washington University in St. Louis, St. Louis, MO;
authors.forename: Raul E
authors.initials: RE
authors.lastname: Martinez
authors.affiliation: School of Engineering and Applied Science, Washington University in St. Louis, St. Louis, MO;
authors.forename: Steven
authors.initials: S
authors.lastname: Dhawan
authors.affiliation: School of Medicine, Washington University in St. Louis, St. Louis, MO.
authors.forename: Walton
authors.initials: W
authors.lastname: Sumner
authors.affiliation: School of Engineering and Applied Science, Washington University in St. Louis, St. Louis, MO; brentw@wustl.edu.
authors.forename: Brent J
authors.initials: BJ
authors.lastname: Williams
mesh_terms: D000336:Aerosols; D002849:Chromatography, Gas / Q000379:methods; D066300:Electronic Nicotine Delivery Systems / Q000706:statistics & numerical data*; D005990:Glycerol; D006801:Humans; D009538:Nicotine / Q000032:analysis*; D019946:Propylene Glycol; D011725:Pyridines / Q000032:analysis*
chemical_list: D000336:Aerosols; D011725:Pyridines; C008615:alpha-nicotyrine; D019946:Propylene Glycol; D009538:Nicotine; D005990:Glycerol