Particle-gas equilibria of ammonia and nicotine in mainstream cigarette smoke

The particle-gas equilibria of ammonia and nicotine in mainstream cigarette smoke have been studied by diffusion denuder collection. The surface depos ition rate of nicotine is observed to decrease as the smoke traverses the d enuder, and this effect is attributed to a changing particle nicotine vapor pressure driven by the measured rapid loss of volatile ammonia from the pa rticles, an interpretation that differs from that of prior studies. The rap id ammonia deposition is observed to be complete at a length-to-flow rate r atio of 28 s/cm(2) for an American blended cigarette, and similar to 38% of the total ammonia analyzed in the collected smoke appears to be nonvolatil e in the aerosol, possibly bound in the particles by reaction with acids. F itting of a theoretical model that predicts the rapid ammonia loss and chan ging nicotine vapor pressure to the measurements predicts that the nicotine vapor pressure over the particles in fresh smoke is about 6% of the pure c omponent nicotine value, and the ammonia vapor pressure over the smoke part iculate is considerably less than that predicted by its aqueous Henry's law coefficient. Dilution of mainstream smoke enhanced the fractional depositi on of both ammonia and nicotine in the denuder tubes and provided a means t o estimate the nonvolatile ammonia fraction, which varied considerably in c igarettes made with different tobacco types. Among the different tobacco ty pe cigarettes, smoke ammonia concentration, "smoke pH," and smoke nicotine- to-particulate ratio varied with ammonia and nicotine deposition from dilut ed smoke when extreme values for an all burley tobacco cigarette were inclu ded in the analysis, but no trends were apparent when only the more typical range of the other cigarettes was considered.