Electron spin resonance and spin trap investigation of free radicals in cigarette smoke: development of a quantification procedure

It has been shown in previous work that free radicals are generated in the mainstream smoke of cigarettes. The most direct method for the detection and quantification of these radicals is electron spin resonance (ESR) spectroscopy in conjunction with the spin trapping method. However, the nature of the spin adduct spectrum and the concentration of the radicals trapped in solution, will vary markedly depending on the experimental conditions employed. In order to apply ESR-spin trapping for analytical experiments in the quantification of free radicals in cigarette smoke, a rigorous set of experimental protocols must be developed. In the current paper, experiments were conducted in order to determine the optimal conditions for maximum signal intensities and reproducibility of results. A set of experimental protocols is therefore described for free radical quantification. These tests were optimised using the University of Kentucky IR4F reference cigarette and also applied to a set of commercial cigarette samples. The results show that radical concentrations in smoke vary amongst cigarettes in both the gas phase and particulate phases. Using the series of commercial cigarettes, where many parameters change from cigarette to cigarette, no statistically significant correlations were found between radical levels and total particulate matter in smoke. However, a weak correlation was found between the gas phase radical levels and total particulate matter levels in smoke. There may also be a complex effect of tobacco type on radical levels in smoke. (C) 2003 Elsevier Science B.V. All rights reserved.