摘要: Electron paramagnetic resonance (EPR) is one of the direct methods for characterizing free radicals. In conjunction with spin trapping technique, EPR is capable of detecting short-lived and chemically active free radicals. In this study, N-tert-butyl-α-phenylnitrone (PBN) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) were used as spin traps to form stable paramagnetic spin adducts during a gas washing procedure to produce EPR signals. Analytical procedures included the evaluation of spin trapping solvents, concentrations of spin traps, etc. Hexane was selected as an optimized solvent for both PBN and DMPO. PBN was used as the basic spin trap to detect the total amount of gas-phase radicals in cigarette mainstream smoke and DMPO as the selective spin trap to detect alkoxyl radicals. The proposed method was applied to 7 unblended tobaccos and a set of commercial cigarette samples. Experimental results showed that radical concentrations in gas-phase smoke varied in different cigarettes and tobacco types.