Determination of Total Ammonia in Mainstream Smoke

Ammonia is generated in mainstream smoke (MSS) from multiple precursors in tobacco such as amino acids, proteins, nitrates and ammonium salts. Ammonia derived from both the particulate and vapor phases is measured with the particulate phase contributing greater than 80% of the total ammonia. The general approach of the analytical methods involved the collection of MSS by either electrostatic precipitation (EP) or impingers with acidic solution combined with Cambridge filters (CF, 44 or 92 mm) and the analysis of ammonium cations by ion chromatography (IC) with a conductivity detector. The available results from both internal testing and external literature for 1R4F Kentucky reference cigarettes, smoked under Federal Trade Commission (FTC) puffing conditions, showed a wide range of yields from approximately 5 to 18 µg/cig of ammonia. To investigate possible causes for this wide range and to optimize the analytical method, several parameters deemed critical to the results were studied using 1R4F. They include the type of acids (hydrochloric acid, sulfuric acid and malic acid), acid strength (0.005 M to 0.1 M), trapping efficiency and sample stability. The study showed that the type and concentration of acids was not significantly related to the total ammonia content in MSS. The study also indicated that the size and type of trapping devices, such as CF pads, acid treated CF pads and EP tube, did not significantly affect the trapping efficiency.