Abstract: A method was developed for rapid determination of 29 pesticide residues in tobacco based on gas chromatography coupled with electron impact ionization mass spectrometric detection (GC-EI/MS). After the optimization of different parameters, such as the extraction solvent, elution solvent, purificant, pesticides were extracted from tobacco with hexane-acetone (1∶1, v/v) in an ultrasonic bath, cleaned-up on a column, packed with Florisil and neutral alumina, eluted with dichloromethane-hexane (95∶5, v/v), and then determined by GC-EI/MS in the selected ion monitoring mode (SIM) with triphenyl phosphate (TPP) as internal standard. The recoveries were performed at 20, 50 and 100 μg/kg fortification levels for each pesticide, and the recoveries ranged from 70% to 110% with the relative standard deviations between 2% and 8%. The detection limits were less than 0.8 μg/kg for 26 pesticides except for the fenpropathrin, deltamethrin and permethrin. The method was linear over the range of 5.0-500.0 μg/kg with the correlation coefficients between 0.9994 to 0.9999. The method was successfully applied to the analysis of these pesticides in tobacco.

Key words: organochlorine, organophosphorous, pesticide residues, pyrethroid, tobacco , gas chromatography-electron impact ionization mass spectrometry (GC-EI/MS)