Residual Analysis of 23 Pesticides in Tea by Microwave Assisted Extraction / Dispersive Solid Phase Extraction Purification and Gas Chromatography- mass Mpectrometry

A gas chromatographic- mass spectrometric(GC- MS) method has been developed for the simultaneous determination of 23pesticide residues in tea. The pesticides included organophosphorus,pyrethroids and herbicides pesticides. The target analytes were extracted with acetonitrile using the microwave- assisted extraction( MAE) and the cleaned up using the dispersive solid phase extraction(DSPE). After being separated on a DB- 17 MS capillary column,the target analytes were detected by GC- MS under the selected ion monitoring( SIM) mode and were quantified by the internal standard method. The correlation coefficents( r2)of 23pesticides were greater than 0. 995 in the concentration range of 0. 01 to 0. 50 mg / L. The limits of quantitation( LOQ) were varied from 0. 005 to 0. 01 mg / kg. It was found that the average recoveries ranged from 70% to 105% at the four spiked levels of 0. 01,0. 05,0. 10,0. 25 mg/kg in blank green tea,and their relative standard deviations(RSDs) were from 3. 0% to 8. 2% under optimized conditions.