Direct introduction of cigarette smoke for puff-by-puff trace metals analysis by inductively coupled plasma mass spectrometry

Abstract

Puff-by-puff on-line analysis of trace metals in mainstream cigarette smoke has been developed by introduction of an aliquot of smoke aerosol directly into an inductively coupled plasma mass spectrometer (ICP-MS) by consecutively puffing a burning cigarette. An automated apparatus consisting of a series of solenoid valves was designed and built, interfacing a smoking machine with an ICP-MS for smoke generation, collection, injection, and analysis. Air, rather than argon, was used as the sample carrier gas to minimize the temporal changes in the plasma characteristics when a discrete smoke aerosol was introduced into the plasma. The measurement precision for the system was about 2.3% RSD (n = 9) for an ambient air sample, based on the peak area of ¹²⁹Xe⁺, in comparison with the 10–50% RSD for the analytes in the smoke matrix sample. The temporal ICP-MS signal profiles behaved differently between analytes in terms of peak growth and decay patterns, which was attributed to differences in their physical forms. For the delivery of trace metals between puffs, As, Cd, and Pb appeared to increase in the later puffs as the cigarette was smoked. In contrast, the lighting puff had more Hg than the next few puffs. The relative deliveries of As, Cd, Hg and Pb in mainstream smoke between two reference cigarettes, 1R4F and 2R4F, were compared with those measured by the conventional methods and showed good agreement. This suggests that the trace metals concentration in cigarette smoke for any test cigarettes can possibly be determined, semi-quantitatively or even quantitatively, by comparison of their signal intensities with those obtained from a reference cigarette with known trace metals concentration in its cigarette smoke.