Abstract:

A method has been developed for the determination of 33 pesticide residues in tea, including organophosphorous, organochlorine and pyrethroid pesticides. The target analytes were extracted with the solution of acetone/dichloromethane (1:1, v/v) using accelerated solvent extraction (ASE) and then purified using gel permeation chromatography (GPC) to eliminate most of the coextracts, such as pigments, lipids and waxes. They were further purified using Carb-NH2 and Florisil solid-phase extraction (SPE) cartridges prior to the identification using gas chromatography-mass spectrometry (GC-MS). The quantitative analysis was performed with flame photometric detector (FPD) for organophosphorous pesticides and electron capture detector (ECD) for organochlorine and pyrethroid pesticides. At the spiked level of 0.05 mg/kg, the recoveries for most pesticides were between 70%-120%; the relative standard deviations were less than 20%; the limits of detection varied from 0.005 to 0.05 mg/kg (defined in terms of 10 times of the baseline noise). This method is precise, sensitive and highly efficient in extraction. After routine applications, the results indicated that this method is suitable for the determination of pesticide residues in the tea for export.

Key words: gas chromatography-mass spectrometry (GC-MS), gel permeation chromatography (GPC), pesticide, residue determination , solid-phase extraction (SPE), tea, accelerated solvent extraction (ASE)