Determination of 39 Organophosphorus Pesticides in Tea by Online Gel Permeation Chromatography-Gas Chromatography Tandem Mass Spectrometry Coupled with Modified QuEChERS Method

The tea sample of 4.000 0 g, acetonitrile of 10.0 mL and 4.00 mg·L^-1 heptachlor epoxide internal standard solution of 400 μL were swirled for 1 min, and extracted ultrasonically for 15 min. After centrifugation, the supernatant of 1.0 mL was taken and toluene of 1 mL was added. The mixture was purified with dispersive solid phase extraction adsorbents containing PSA of 30 mg, C₁₈ of 30 mg, GCB of 15 mg, and anhydrous magnesium sulfate of 150 mg, and 39 organophosphorus pesticides in the purified solution were determined by online gel permeation chromatography-gas chromatography tandem mass spectrometry (Online GPC-GC-MS/MS). As shown by the results, linear relationships of 39 organophosphorus pesticides were found in definite ranges, with detection limits (3S/N) in the range of 0.5-4.3 μg·kg^-1. Test for recovery was made by standard addition method, giving results in the range of 83.1%-105%, with RSDs (n=6) all less than 9.0%.