Investigation of Free Radicals in Cigarette Mainstream Smoke

Electron Paramagnetic Resonance spectroscopy (EPR) coupled with spin trapping methodology has been used to study the formation of free radicals in mainstream cigarette smoke. Kentucky reference cigarettes (2R4F) were smoked using a 20-port smok­ ing machine (Borgwaldt-kc) under ISO smoking conditions. Free radicals in both particulate phase and gas phase smoke were analysed. Short-lived Cand O-centred radicals were detected in the gas-phase, while in the particulate phase, persistent quinonic radicals were identified. In addi­ tion, the oxidation of the particulate phase smoke with a stable hydrazyl radical generated short-lived radicals, which were trapped by DMPO. The mixture contained predominantly O-centred radicals with smaller amounts of Cand N-centred radicals. Hyperfine coupling constants of the radicals were compiled and the ratios of different species in the mixture were determined by simulation.