Author

Cai Chen

Date

July 2006

Document Type

Dissertation

Degree Name

Ph.D.

Department

Dept. of Environmental and Biomolecular Systems

Institution

Oregon Health & Science University

Abstract

Nicotine is recognized as the tobacco component that is responsible for most if not all of the addictive nature of tobacco. In mainstream tobacco smoke (MTS), the amount of nicotine that is in the free-base form is generally believed to be well correlated with physical “impact”, “strength”, and “harshness” of such smoke. There are also reasons to expect that the amount of free-base nicotine may be related to the addictiveness of tobacco smoke. Evidence from previously secret tobacco industry documents indicates that ammonia-producing compounds have been added to cigarette tobacco as “impact boosters”. Knowledge of the acid/base chemistry of tobacco smoke is required for a proper understanding of the effect of ammonia additives on nicotine chemistry in MTS. The goal of this work was to improve our understanding of this chemistry by studying the interdependent gas/particle (G/P) partitioning of nicotine and ammonia in MTS, including the study of components in MTS that are related to the chemistries of nicotine and ammonia (organic amides). In the theoretical portion of this work, equations describing the interdependent G/P partitioning of ammonia and nicotine in MTS were derived using established acid/base theory, together with G/P partitioning theory. The G/P partitioning coefficient of free-base ammonia ( a p, fb K ) and the activity coefficient of ammonia were estimated using existing data, including values of the G/P partitioning coefficient of free-base nicotine ( n p, fb K ). It was predicted that a p log K and n p log K will tend to be linearly correlated for typical MTS samples. In the experimental portion of this work, samples from eleven brands of cigarettes and two brands of cigar-like products were machine-smoked according to a standard protocol and the MTS was collected. The levels of ammonia and nicotine in both the gas phase and particulate matter (PM) of MTS were measured along with other parameters, including the levels of water and other acid-base relevant components in the PM. The analytical methods used were specially developed for this work. For example, extraction of MTS PM for determination of ammonia was carried out using 2-propanol to avoid hydrolysis of labile, ammonia-containing smoke compounds such as amides. Generally, the cigar-like products delivered higher per-puff amounts of ammonia than did the cigarettes; the delivered levels of nicotine were similar across all products tested. The measured n log K p were found to be negatively correlated with total ammonia delivery, suggesting that increasing ammonia levels in MTS can increase the percentage of the nicotine that is found in the gas phase. During the consideration of the advantages of 2-propanol as the extraction solvent for ammonia from MTS PM, it was confirmed that the use of water (with or without added acid) could trigger the ammonia-releasing reactions during extraction. Several lines of evidence were obtained that strongly suggest that these reactions are hydrolytic in nature. For example, the release rate increases with the acidity of the aqueous extraction solvent. Possible tobacco smoke reactants for the hydrolysis reactions include amides, nitriles and other neutral nitrogen-containing compounds. The presence of two specific amides was confirmed by two-dimensional gas chromatography (GCxGC) gas chromatography coupled to a time of flight mass spectrometer (ToFMS). Since the formation of an amide by combination of ammonia with an organic acid will serve to neutralize the acid, the presence of amides in tobacco smoke is highly relevant to the study of the acid/base dependent G/P portioning of both ammonia and nicotine. The experimentally observed correlation of a p log K vs. n p log K is highly consistent with theoretical predictions made here. This confirms the importance of acid/base chemistry in controlling the G/P partitioning of both ammonia and nicotine in MTS. This conclusion also indicates that the theories and assumptions developed here are generally appropriate for the study of acid/base chemistry of MTS.

Identifier

doi:10.6083/M48G8HMF

School

OGI School of Science and Engineering

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