Abstract: A gas chromatography-mass spectrometry (GC-MS) method was developed for the simultaneous determination of 72 pesticides and their isomers including organochlorine, pyrethriod, organophosphorus and other pesticides in tea. After moistened by water, the samples were subjected to extraction by acetonetrile, preliminary clean up by 5 g/100 mL sodium chloride, and further purification on carbon/NH2 column through the elution using 25 mL of ethyl acetate-acetone (1:1). The MS detection was performed in the selected ion-monitoring mode under the optimal chromatographic conditions. The recovery rates were determined in samples spiked at 0.1 mg/kg and 1.0 mg/kg. The overall recovery rates were 65.3%－142.3%, with a relative standard deviation (RSD) between 3.0% and 20.6%. The detection limit of this method was 0.01－0.08 mg/kg with a signal/noise ratio of 3. This developed method is characteristics of high sensitivity and accuracy, which is suitable for the simultaneous determination of pesticide residues.

Key words: tea, GC-MS, multiple residues, LLE, SPE