Composition Studies on Tobacco XXXIII Changes in Smoke Composition and Filtration by Artificial Alteration of Smoke pH: Pyridine and Nicotine

Using selected additives, the pH of smoke from U.S. commercial cigarettes (5.6) can be altered over a wide range (4.1-8.2). The volatility of the additive is of greater importance in changing smoke pH than the acidic or basic strength of the additive. The activated carbon in multiple carbon-cellulose acetate filters is highly effective in removing pyridine selectively from the smoke of blended commercial cigarettes. The degree of this selectivity is markedly reduced on lowering the smoke pH to 4.1 by adding formic acid to cigarettes. On raising the pH of smoke to 8.2 by adding dipropylamine to cigarettes, the selectivity for pyridine is less than in smoke of unaltered pH and more than in smoke of pH 4.1. Some selectivity of nicotine removal is observed in the alkaline smoke using cellulose acetate filters with or without carbon. The use of formic acid to depress pH appears to alter the kinetics of nicotine pyrolysis, resulting in a changed nicotine : pyridine ratio.