Composition Studies on Tobacco XXXlX: Changes in Smoke Composition and Filtration by Artificial Alteration of Smoke pH: Formic and Acetic Acids and Volatile Phenols

The levels of formic and acetic acids in the free acid and salt forms in unfiltered smoke are reduced when smoke pH is lowered from 5.6 to 4.2 using lactic acid as the cigarette additive. The acid levels are increased markedly when unfiltered smoke is alkalinized to pH 8.2 using dipropylamine as the cigarette additive. The variability of the analytical method prevented detection of small degrees of selective filtration of the acids. Although indications of selective removal were obtained in smoke of pH 4.2-7.9, using cellulose acetate filters with or without activated carbon, the variability did not permit a firm demonstration of this effect with one exception: a distinct selective removal of acetic acid was observed in smoke of pH 4.2 using a multiple filter. The use of formic acid as a cigarette additive to lower the pH of unfiltered smoke results in a significant increase in the major phenols therein. No change in levels of smoke phenols is observed when dipropylamine is used as a cigarette additive to alkalinize the smoke. An increase in selective removal of smoke phenols occurs when smoke pH is depressed from 5.8-6.1 to 4.4-4.9 using filters of cellulose acetate with or without activated carbon. Selectivity is lost when smoke pH is raised to 7.9 using the alkaline cigarette additive.