Abstract:

A method has been developed for the simultaneous detection of nine pyrethroid pesticide residues in tea by gas chromatography-tandem mass spectrometry (GC-MS/MS) combined with accelerated solvent extraction (ASE) and solid-phase extraction (SPE). The pesticide residues in tea were extracted using acetone/n-hexane (1:1, v/v) for 5 min at 100℃ before preheating the extraction pool for 3 min, under extractive pressure of 10 MPa for one cycle. After extraction, the extraction pool was washed with acetone/n-hexane (1:1, v/v) having volume of 40% of the pool volume, followed by purging for 100 s with nitrogen. The extract was purified by a Cleanert TPT solid-phase extraction column. After purification, the target compounds were detected by GC-MS/MS and quantified by the external standard method. Under the optimized conditions, good linearities were obtained for the nine pyrethroid pesticides in the range of 2-1000 μg/L, with correlation coefficients exceeding 0.99. The limits of detection (LODs) were 0.2-4.5 μg/kg and the limits of quantitation (LOQs) were 0.8-15.0 μg/kg. At four spiked levels (0.02, 0.1, 0.4 mg/kg, and the LOQ level) in green tea and black tea, the recoveries of all the pesticides were between 69.87% and 110.0%, with relative standard deviations (RSDs) varying from 0.7% to 11.2%. This method effectively reduces the matrix interference and shows high sensitivity, good reproducibility, and stable recovery, and can thus be used for the detection of pyrethroid pesticide residues in tea.

Key words: accelerated solvent extraction (ASE), gas chromatography-tandem mass spectrometry (GC-MS/MS), pyrethroid pesticides, tea