Listed versus measured nicotine contents, molar acid/nicotine ratios and free-base fraction (αfb) 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%* (listed/measured) | Nictot (mg/mL) (measured) | Acid† | Molar acid†/nicotine ratio (CHA/CNic) | αfb‡ |
| JUUL ‘pods’ (5% nicotine by wt.) | |||||
| JUUL ‘Cool Mint’/JUUL(8) group | 5.0/5.1 | 60 | BA | 0.97 | 0.13 |
| JUUL ‘Classic Menthol’/JUUL(8) group | 5.0/4.9 | 58 | BA | 0.98 | 0.13 |
| JUUL ‘Crème Brûlée’/JUUL(8) group | 5.0/5.1 | 60 | BA | 0.97 | 0.12 |
| JUUL ‘Fruit Medley’/JUUL(8) group | 5.0/5.0 | 59 | BA | 0.99 | 0.12 |
| JUUL ‘Cool Cucumber’/JUUL(8) group | 5.0/5.0 | 59 | BA | 1.00 | 0.11 |
| JUUL ‘Classic Tobacco’/JUUL(8) group | 5.0/5.0 | 59 | BA | 1.00 | 0.11 |
| JUUL ‘Virginia Tobacco’/JUUL(8) group | 5.0/5.1 | 60 | BA | 1.00 | 0.11 |
| JUUL ‘Mango’/JUUL(8) group | 5.0/5.2 | 62 | BA | 0.99 | 0.09 |
| JUUL ‘pods’ (3% nicotine by wight) | |||||
| JUUL ‘Virginia Tobacco’/JUUL(2) group | 3.0/3.0 | 35 | BA | 0.94 | 0.14 |
| JUUL ‘Mint’/JUUL(2) group | 3.0/3.0 | 35 | BA | 1.04 | 0.11 |
| For 10 JUUL liquids: ave.±1 SD | 0.12±0.01 | ||||
| Other ‘nicotine salt’ formulation ‘pods’ | |||||
| EM | 6.0/4.0 | 47 | BA | 3.43 | 0.00§ |
| SS | 5.0/4.3 | 51 | BA | 1.02 | 0.09 |
| ZiC | 5.0/3.3 | 38 | BA | 4.03 | 0.01§ |
| ZiM | 5.0/3.5 | 41 | BA | 3.71 | 0.00§ |
| FF | 5.0/2.3 | 27 | BA | 0.76 | 0.15 |
| ZA | 5.0/4.5 | 53 | LA | 0.22¶ | 0.19§ |
| ZMI | 5.0/4.4 | 52 | LA | 0.29¶ | 0.17 |
| ZC | 5.0/4.8 | 57 | LA | 0.25¶ | 0.14 |
| Nicotine salt bottled e-liquids | |||||
| Fuji-50 | 4.2/4.2 | 50 | U | U | 0.08 |
| BRL-50 | 4.2/4.1 | 49 | U | U | 0.01 |
| Fuji-25 | 2.1/2.0 | 24 | U | U | 0.08 |
| BRL-25 | 2.1/2.1 | 25 | U | U | 0.02 |
| Non-‘salt’ bottled e-liquids | |||||
| Ec-24 | 2.0/1.0 | 12 | – | U | 0.98§ |
| RwC-24 | 2.0/2.8 | 33 | U | U | 0.70 |
| UB-24 | 2.0/0.9 | 11 | U | U | 0.84 |
| Ec-6 | 0.5/0.5 | 5 | – | U | 0.96 |
| UBP-6 | 0.5/0.4 | 5 | U | U | 0.53 |
| UB-6 | 0.5/0.4 | 5 | U | U | 0.43 |
| RwC-6 | 0.5/0.5 | 6 | U | U | 0.08 |
*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 αfb 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’; CHA, total molar-based concentrations of HA; CNic, total molar-based concentrations of nicotine; Ec-6, Fuzion Vapor ‘Ectoplasm’; Ec-24, Fuzion Vapor ‘Ectoplasm’; EM, Eon Smoke ‘Mango’; αfb, 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’.