No abstract

A modifi ed QuEChERS method was developed and validated for determination of pesticide multi-residues in green tea by liquid chromatography tandem mass spectrometry. Lead acetate was fi rst time used together with primary secondary amine and graphite carbon black to eliminate tannin, caffeine, and other pigments in tea and thus reduced the matrix effects. The method was compared to the original QuEChERS method as well as A.O.A.C. QuEChERS method. For accurate quantifi cation, the matrix matched calibration technique was used. The method showed good performance in the concentration range from 0.01 to 1 mg kg -1. All pesticides could be quantifi ed at and lower than 0.01 mg kg -1 . Recoveries were from 70 to 120% and repeatabilities were <15% RSD depending on the compounds.