Nicotine addiction and the sensory impact of tobacco smoke are strongly influenced by the fraction of nicotine present in its free-base form. This work examines the acid–base chemistry governing the interdependent gas/particle partitioning of nicotine and ammonia in mainstream tobacco smoke, motivated by evidence that ammonia-producing additives are used to enhance smoke “impact.” Using established acid–base and partitioning theory, equations describing the coupled behavior of nicotine and ammonia were derived, and key partitioning and activity coefficients were estimated from existing data. The model predicts a linear correlation between nicotine and ammonia partitioning, improving understanding of how additives influence nicotine chemistry and smoke characteristics.
