GC-MS/MS Determination of Residual Amounts of 33 Pesticides in Tea with Purification by Gel Permeation Chromatography and Solid Phase Extraction

Tea sample was extracted with ethyl acetate-cyclohexane mixture (1+1) using high-speed homogenization. The crude extract obtained was purified succesively by GPC and SPE to eliminate pigments, lipids, waxes and other impurities. Eluate from the SPE column was evaporated to near dryness, and the residue was dissolved with 1 mL of acetone which was introduced into the instrument and analyzed by GC-MS/MS, using the MRM mode and external standard method for quantification. Lower limit of determination (10S/N) of the 33 pesticides were found all less than 0.01 mg·kg-1. Tests for recovery was performed by addition of 0.01 mg·kg-1 of standards of the 33 pesticides, giving values of recovery in the range of 75%-116%, with RSD′s (n=5) all less than 10%.