Table 2.

Values of K _{oa, 1} (40°C) for benzoic acid and vanillin in e-liquid formulations.

C HA/CNic	α fb	K oa,1	Log K oa,1
Benzoic acid
JUUL ‘Cool Mint’ (5% nicotine)	0.97*	0.13	58	1.77
JUUL ‘Classic Menthol’ (5% nicotine)	0.98*	0.13	53	1.72
JUUL ‘Crème Brûlée’ (5% nicotine)	0.97*	0.12	72	1.86
JUUL ‘Fruit Medley’ (5% nicotine)	0.99*	0.12	59	1.77
JUUL ‘Cool Cucumber’ (5% nicotine)	1.00*	0.11	65	1.82
JUUL ‘Classic Tobacco’ (5% nicotine)	1.00*	0.11	65	1.82
JUUL ‘Virginia Tobacco’ (5% nicotine)	1.00*	0.11	65	1.82
JUUL “Mango” (5% nicotine)	0.99*	0.09	115	2.06
JUUL “Virginia Tobacco” (3% nicotine)	0.94*	0.14	66	1.82
JUUL ‘Mint’ (3% nicotine)	1.04*	0.11	48	1.68
Averages for JUUL	0.99±0.03 SD	0.12±0.01	67±18	1.81±0.10
43/57 PG/GL (by wt.)+nicotine+benzoic acid (final nicotine level=4.6 wt%)	1.01	0.16	26	1.41
32/68 PG/GL (by wt.)+nicotine+benzoic acid (final nicotine level=4.6 wt%)	1.03	0.14	31	1.49
32/68 PG/GL (by wt.)+nicotine+benzoic acid+5% (by vol.) water (final nicotine level=4.5 wt%)	1.03	0.11	51	1.71
Vanillin
45/55 PG/GL (by wt.)+nicotine+vanillin  (final nicotine level=5.1%)	0.50	0.95	0.0058	−2.23
45/55 PG/GL (by wt.)+nicotine+vanillin  (final nicotine level=5.1%)	1.02	0.91	0.0089	−2.05
45/55 PG/GL (by wt.)+nicotine+vanillin  (final nicotine level=4.9%)	1.51	0.88	0.0120	−1.92
Averages for vanillin		Ave.±1 SD	0.0089±0.0025	−2.07±0.13

*By liquid chromatography for both nicotine and benzoic acid, using a method discussed elsewhere.¹⁵

ave, average; C _HA, total molar-based concentrations of HA; C _Nic, total molar-based concentrations of nicotine; α _fb, fraction of nicotine in the free-base form; GL, glycerol; PG, propylene glycol; vol., volume; wt., weight.