Determination of 56 Pesticides in Black Tea by GC-MS/MS with Timed SRM
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Abstract:
A novel method was developed for simultaneous determination of methamidophos and other 55 pesticides in black tea using gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS). The extraction effects of different extraction regents were compared and the purifying effects of Cleanert TPT Solid phase extraction column and QuEChERS were also investigated. The optimum pretreatment conditions for the tea samples were determined as follows: extracting the tea samples by n-hexane: acetone (7:3, V/V) followed by Cleanert TPT column purification. After purified by Cleanert TPT solid-phase extraction tube, the signal-noise ratios of 54 pesticides were improved by two times. The purified samples were then analyzed by GC-MS/MS with “timed SRM” mode, and quantified by internal standard method. Timed SRM can solve the data shortage and quantitative accuracy problem caused by traditional MRM method. The limits of detection were in the range of 1 μg/kg to 18 μg/kg. At the spiked levels of 3 μg/kg to 600 μg/kg, the recoveries of 55 pesticides (except methamidophos)ranged from 73% to 126% with the relative standard deviation less than 18% (n=6). The results demonstrated that this method was accurate and effective, suitable for the determination of 56 pesticides residues in black tea.
