Abstract: A novel method for the determination of 5 pyrethroid pesticide residues in tobacco leaf and tea samples was established. The pesticide residues in the samples were extracted and concentrated with stir bar, desorbed by thermal desorption system, and then determined by gas chromatography-mass spectrometry (GC-MS). The pesticide residues in the samples were extracted with a stir bar at 1100 r/min for 1 h. The desorption was carried out at 300 ℃ for 4 min under a helium flow of 50 mL/min while maintaining a cryofocusing temperature of 0 ℃ in the CIS-4 injector of the GC-MS system. Finally, the CIS-4 injector was raised to a temperature of 300 ℃ and then the analytes were separated by GC and detected by MS. The limits of detection of this method for the tobacco leaves ranged from 3.3 ng to 11.4 ng. The recoveries of pesticides from the tobacco leaves ranged from 94.8% to 103.4% and the relative standard deviations (RSDs) of peak areas ranged from 5.3% to 8.6% (n=6). The limits of detection of this method for tea ranged from 4.2 ng to 10.5 ng. The recoveries of pesticides from tea ranged from 98.2% to 110.1% and the RSDs of peak areas were less than 9.6% (n=6). Therefore, this method can satisfy the requirements for the rapid analysis of pesticide residues in the tobacco leaf and tea samples.

Key words: gas chromatography-mass spectrometry (GC-MS), pesticides residues, pyrethroid, tea , thermal desorption, tobacco leaves, stir bar sorptive extraction