Multiresidue determination of 17 organochlorine and pyrethroid pesticides in tea by gas chromatography-negative chemical ionization-mass spectrometry
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An analytical multiresidue method for the simultaneous determination of 17 pesticides(8 organochlorines and 9 pyrethroids) in tea was developed. Pesticides were extracted from tea with hexane-acetone (volume ratio is 1: 1) in an ultrasonic bath and cleaned up on a Florisil and neutral alumina column, then were determined by gas chromatography with negative chemical ionization mass spectrometric detection in the selected ion monitoring mode, and with heptachlor epoxide as the internal standard. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. The recovery studies were performed at 20, 50 and 200 mu g/kg fortification levels for each pesticide, and the recoveries ranged from 67.9% to 129% with a relative standard deviation between 1.0% and 20% for the different pesticides. The detection limit of the method was less than 1.0 mu g/kg for most of pesticides except for the permethrin. The developed method was linear over the range assayed, 10-500 mu g/L, with determination coefficients > 0.996. Finally, the developed analytical method was successfully applied to the determination of pesticides in several tea samples.