[Determination of 53 pesticide residues in tea by gas chromatography-tandem mass spectrometry and double internal standard method].

A gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) method with tandem double columns was established for the determination of 53 pesticide residues in tea. The sample was extracted by acetonitrile with buffering salts of QuEChERS method, cleaned up with an ENVI-Carb/NH solid-phase extractant, and determined by GC-MS/MS. To reduce the matrix effect in GC-MS/MS, gulonic acid lactone and sorbitol were added to the standard solutions as protectants; additionally, anthraquione-D8 and triphenyl phosphate were used as double internal standards. The linear ranges were from 20 to 500 μg/L for 52 pesticides, and from 40 to 1000 μg/L for cypermethrin, with correlation coefficients higher than 0.99. The limits of quantification (LOQs) of 28 pesticides were less than 10 μg/kg, and the LOQs of the other 25 pesticides ranged from 10 to 20 μg/kg. The recoveries were in the range 72.5%-130.9%, and the relative standard deviations (RSDs) were in the range 0.4%-19.4%. This method is simple, rapid, sensitive, and reliable for the simultaneous identification and quantification of multiple residues in tea.