Smoke-derived chemiluminescence as phenomenon and experimental tool
Chemiluminescence emission can be detected from cigarette smoke. This is thought to link to smoke free radicals, many of which are reactive oxygen and nitrogen species of excited states. Smoke-derived chemiluminescence was first observed in the mid-1970s, however, to date its mechanistic nature remained unclear. A comprehensive knowledge on the nature of the excited state generation in smoke is required if facile chemiluminescence assays are to be developed into an analytical tool for studying the free radical content of cigarette smoke and its oxidative potential. The present study used commercial cigarettes of different tar levels available in Russia. The mainstream whole smoke was generated using a syringe simulating the machine-smoking condition using 35 mL puff volume, 2-s puff duration and one puff every 60 s. The experimental results provided insight into the general mechanism of the mainstream cigarette smoke derived chemiluminescence, which involved excited state generation in unimolecular transformation of smoke borne free radical species. However, the concentration of these radicals was found to obey a bimolecular (second-order) kinetics and depended on the amount of total particulate matter (TPM). Surprisingly, no energy transfer took place from the primary excited light-emitting species to luminophoric molecules in the smoke. The implications of the results are discussed in relation to the free radical activities in smoke.