Determination of Cypermethrin and Fenvalerate Residues in Tea by Reversed-Phase High Performance Liquid Chromatography

A method for rapid determination of cypermethrin and fenvalerate residues in tea sample by reversedphase high performance liquid chromatography was proposed. The pyrethroids in tea sample were first extracted at 40 ℃ by a mixture of V(hexane)∶V(acetone)=97.5∶2.5. And then, the extract was puried by a column (5 mm×70 mm) packed with 320 mg florisil and toppacked with 15 mg active carbon. V(Petroleum ether mixed)∶V(acetic ether)=9∶1 was selected as eluant. The HPLC operating conditions were Hypersil ODS column, V(acetonitrile)∶V(water)=74∶26 as mobile phase with the flow rate of 1.2 mL·min-1 and UV detection wavelength at 198 nm. The pyrethroids were analyzed by HPLC with diode assay detector under optimun conditions and quantified by external standard calibration method. Recoveries of cypermethrin and fenvalerate in tea samples are 71.0% and 76.0%, respectively. Relative standard deviation (n=6) are 2.5% for cypermethrin and 2.2% for fenvalerate.