Table 1

Listed versus measured nicotine contents, molar acid/nicotine ratios and free-base fraction (α fb) for a selection of JUUL pod liquids, ‘look-a-like/knock-off’ pod liquids, and bottled e-liquids (additional details can be found in online supplementary table S-1).

Brand ‘flavour’Nicotine wt%*
Nictot (mg/mL) (measured)Acid†Molar acid†/nicotine
ratio (C HA /C Nic)
α fb
JUUL ‘pods’ (5% nicotine by wt.)
 JUUL ‘Cool Mint’/JUUL(8) group5.0/5.160BA0.970.13
 JUUL ‘Classic Menthol’/JUUL(8) group5.0/4.958BA0.980.13
 JUUL ‘Crème Brûlée’/JUUL(8) group5.0/5.160BA0.970.12
 JUUL ‘Fruit Medley’/JUUL(8) group5.0/5.059BA0.990.12
 JUUL ‘Cool Cucumber’/JUUL(8) group5.0/5.059BA1.000.11
 JUUL ‘Classic Tobacco’/JUUL(8) group5.0/5.059BA1.000.11
 JUUL ‘Virginia Tobacco’/JUUL(8) group5.0/5.160BA1.000.11
 JUUL ‘Mango’/JUUL(8) group5.0/5.262BA0.990.09
JUUL ‘pods’ (3% nicotine by wight)
 JUUL ‘Virginia Tobacco’/JUUL(2) group3.0/3.035BA0.940.14
 JUUL ‘Mint’/JUUL(2) group3.0/3.035BA1.040.11
For 10 JUUL liquids: ave.±1 SD0.12±0.01
Other ‘nicotine salt’ formulation ‘pods’
Nicotine salt bottled e-liquids
Non-‘salt’ bottled e-liquids
  • *Calculated by integrating 1H NMR resonances for nicotine relative to propylene glycol and glycerol resonances in each e-liquid and obtaining the mole per cent values, which were then converted into wt% values. These values do not reflect the variable presence of water, accounting for water affecting nicotine mg/mL by less than ~10%.

  • †Values by liquid chromatography for JUUL products, by NMR for all others. Ratio computed based on the main acid contributor for each liquid.

  • ‡Different chemical shift references were used based on composition. The value presented is that for the average at 40°C. For details, see the Methods section.

  • §Only one α fb value was obtained by 1H NMR due to either resonance overlap or peak broadening.

  • ¶Incomplete characterisation of the acid content.

  • ave., average; BA, benzoic acid; BRL-25, Salt Bae50 ‘Blue Raspberry Lemonade’; BRL-50, Salt Bae50 ‘Blue Raspberry Lemonade’; C HA, total molar-based concentrations of HA; C Nic, total molar-based concentrations of nicotine; Ec-6, Fuzion Vapor ‘Ectoplasm’; Ec-24, Fuzion Vapor ‘Ectoplasm’; EM, Eon Smoke ‘Mango’; α fb, fraction of nicotine in the free-base form; FF, SMPO ‘Full Fruit’; Fuji-25, Pacha Mama Salts ‘Fuji’; Fuji-50, Pacha Mama Salts ‘Fuji’; LA, levulinic acid; Nictot, total nicotine concentration; NMR, 1H NMR spectroscopy; RwC-6, Fuzion Vapor ‘Roundhouse with Cream’; RwC-24, Fuzion Vapor ‘Roundhouse with Cream’; SS, Myle ‘Summer Strawberry’; U, unknown/undetected; UB-6, Fuzion Vapor ‘Unicorn Blood’; UB-24, Fuzion Vapor ‘Unicorn Blood’; UBP-6, Fuzion Vapor ‘Unicorn Blood Prime’; wt%, weight per cent; ZA, ZOOR ‘Apple’; ZC, ZOOR 'Cake'; ZiC, ZiiP ‘Cappuccino’; ZiM, ZiiP ‘Mango’; ZMI, ZOOR ‘Mint Ice’.