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Analysis of the Acid-Base Balance of Mainstream Tobacco Smoke and its Effect on the Gas/Particle Partitioning of Nicotine

Tobacco smoke particulate matter (PM) is a complex mixture of condensed organic compounds, with about 5 to 10% water. Its general properties are similar in some respects to that of atmospheric organic aerosol PM and thus provides a useful surrogate when studying atmospheric PM. Due to its ability to undergo acid-base chemistry, nicotine is of particular interest in the tobacco smoke system. The gas/particle partitioning of nicotine depends on the protonation state of nicotine in the particles, so the distribution of nicotine between these phases provides a means of understanding the acid-base balance in the tobacco smoke system. The goal of this work is to develop an acid-base balance for mainstream tobacco smoke that accounts for the extent of protonation of nicotine.
Samples of extracted smoke particulate matter from seven brands of cigarettes were analyzed by ion chromatography (IC) and titration by both acid (HCl) and base (lithium phenoxide) for comparison with nicotine data collected by colleagues. IC analysis was used to quantify tracers of known acidic and basic species in tobacco smoke. Anion tracers for acids included: glycolate, acetate, formate, lactate, chloride, nitrite, sulfate, and nitrate. The cation tracers for base were ammonium, sodium, and potassium. The tobacco smoke extracts were also analyzed after acidification by the HCl titrant for changes in ammonia and organic acid concentrations to determine whether "bound" forms of these compounds were present in the PM. The titration data provided total concentrations of weak acid and bases in the samples. This titration data was compared with the concentrations of the tracers for weak acids and bases (along with the quantification of total nicotine by colleagues) to determine whether the IC analyses were accounting for all of the important species. The results of this comparison show that these analyses missed relevant species in the tobacco smoke system.
As tobacco smoke PM is a complex organic mixture, the ability of acid species to protonate nicotine will be different than in aqueous media. The acidic species of interest were assumed to be either strong or weak, with the strong species assumed to be fully ionized after protonation of nicotine. Some portion of the weak acid species could then protonate any available nicotine. An electroneutrality equation (ENE) was developed for the tobacco smoke PM and populated using the IC data and the nicotine data obtained by colleagues. Using this ENE, the extent ionization of the weak acids species (α1A) and the net reaction constant for the protonation of nicotine by these weak acids (K*) was estimated. However, interpretation of the results were complicated by the underrepresentation of the pertinent weak acid species in our IC analyses.
This study concluded that further work is needed to identify the missing weak acid and base species to obtain a better representation of the acid-base balance in tobacco smoke PM and to understand the ability of these weak acid species to protonate nicotine.
Date20 November 2017
CreatorsDeVita-McBride, Amy Kathleen
Source SetsPortland State University
Detected LanguageEnglish
SourceDissertations and Theses

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