The draft guidance for PMTA submissions for ENDS (e-cigarettes and similar products) has stirred much discussion because of the costs and technical complexity of procedures set forth in the guidance. At Lines 1060-61 of the Draft Guidance, the FDA wrote, “In addition to the constituents, FDA recommends that you report the pH of the e-liquids tested and the resulting aerosol.” Typical e-liquids are 85 -90% mixtures of glycerol and/or propylene glycol (PG) with the balance being flavors, nicotine, and water. Use of the US CDC procedure for the determination pH-values of of smokeless tobacco for the determination of e-liquid pH as reported by several FDA scientists results in unstable pH readings and cloudy suspensions with mentholated e-liquids. Moreover the pH-value of the bulk e-liquid is not necessarily reflective of its use in a device. Thus, we have developed a technique based on nonstandard pH electrodes. We have evaluated several pH electrodes designed for nonstandard applications such as food, fabric, and other low-water matrices. This evaluation was done with commercial rechargeable e-cigarettes (so-called “cigalikes” such as V2, Mark Ten XL, and Green Smoke) and an aerosol trap designed after the one used for Health-Canada Method T-113 (pH cigarette smoke). The trap was connected to an e-cigarette smoking machine designed to meet the requirements of CORESTA Recommended Method No. 81 (55-mL square-wave puff/3-s duration/30-s puff interval). As the e-cigarette aerosol enters the trap, it is directed upwards to the sensing elements of the pH electrodes. Steady-state concentration of the aerosol is achieved after 15 to 20 puffs and the pH-value of the e-liquid is the value obtained after 25 puffs (pH values obtained with a Hach H260G meter connected to a PC). The best electrodes found to date are the Hanna Instruments HI 1314B (a modified flat-bottom glass electrode) and the Horiba Laqua (flat-bottom) ISFET electrode, The keys to this technique is establishing a thin film of pH 6 buffer diluted with water/glycerol/PG. This step provides a conductive film across the bottom of the probe and a starting pH for the pH-determinations. Moreover, observed pH values can also be compared with values obtained using e-liquids of known mixtures of nicotine, glycerol, propylene glycol, and water placed is blank cartomizer sections of the e-cigarettes.

Use of nonstandard pH electrodes for the determination of pH-values of e-cigarette aerosols to comply with requiremnts specified in USFDA draft guidance on Premarket Tobacco Product Applications (PMTA) for Electronic Nicotine Delivery Systems (ENDS)

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.