Selected inorganic chemical composition of mainstream cigarette smoke as a function of aerodynamic particle size

Abstract

Described is a new method for studying the inorganic chemical composition of various fractions of mainstream smoke separated according to particle diameter. University of Kentucky 1R1 reference cigarettes were neutron activated in a 2MW swimming pool reactor. These activated cigarettes were then smoked on a conventional reverse puffing machine and the smoke immediately diluted 200: 1 with clean air. The diluted smoke was then separated into fractions based on particle diameter in a spiral centrifuge. The separate fractions were subsequently counted on a Ge(Li) detector coupled to the proper electronics, multichannel analyzer, and dedicated computer system. Data is presented showing the relative concentration ratios of K, Na, Cl, Br and Mn. Total sulfur was assayed by long-term low-background scintillation counting. The neutron activation analyses results show that the relative ratio of Na, Cl, Br, and Mn to K remains constant regardless of size from 0.1 to 2 μm aerodynamic particle diameters. Sulfur shows a definite chemical variability compared to the other measured inorganics and is enriched in the smaller particle sizes below 0.3 μm. Total carbon was also analyzed and data is shown which compares the relative ratios of K, Na, Cl, Br, S and Mn to the total carbon content. Sulfur is enriched compared to carbon in the 0.5 μm and smaller particles. The K, Na, Cl, Br and Mn show depletions compared to carbon in both the small and large particles, but an enrichment in the 0.3–0.7 μm particles. A comparison of the inorganic ratios in dropped cigarette ash and the ionic portions of the sized mainstream smoke aerosol is presented. A possible mechanism is presented to explain how the major mass amounts of the inorganics studied are transferred to smoke. This mechanism is one of a mechanical “entrainment” of pieces of inorganic residue that during the cigarette puff, break off from the coal and are transferred into the smoke stream. The “entrained” inorganic residue is subsequently regulated in its size distribution by the normal impaction filtration mechanisms of the tobacco column. These sized “entrained” inorganics then exit in the mainstream smoke. Because the bulk of these particles is made up of the “entrained” inorganic residue, they account for the major chemical mass of the inorganics studied, while the other mechanisms of inorganic transfer (volatilization, condensation, and nuclei contributions) are shown to be of minor importance to the overall chemical transfer.