Any pH determination to measure the effective acid-base properties of an aerosol is dependent on the measurement technique. Determinations of aerosol pH using puff-by-puff collections are influenced by the buffer used to condition the electrode, while measurements of aqueous extracts of aerosol collected on glass-fibre filter pads are influenced by the background from the pad. Utilizing the water soluble properties of the e-aerosol matrix, the pH of aerosol trapped directly into an aqueous solution can be measured, with the measured pH being more consistent with that determined for the e-liquid.

In this study, aerosol generated from the puffing of electronic cigarettes was passed through a liquid trap (70 mL fritted impinger) containing 25 mL of a 1 % (w/v) NaCl degassed aqueous solution. The pH of the resulting solution was measured using a pH meter and combination electrode. Multiple products, anticipated to contain e-liquid of different pH, were puffed using two regimes for three different collection segments.

Accuracy for aerosol pH could not be determined. At best, a comparison between the measured pH of the aerosol and the pH determined for the e-liquid, in combination with precision of the measurements, was used as some measure of the ‘pseudo-accuracy’ of the method. The method collection system demonstrated excellent repeatability and reproducibility (<5 %) independent of the puffing regime. The measured aerosol pH was influenced by both the aerosol amount, measured by device mass loss, and the total collection volume.

This technique was determined to be suitable for comparing the effective acid-base properties of the aerosol generated from the puffing of electronic cigarette devices.