Determination of multi-pesticide residues in green tea with a modified QuEChERS protocol coupled to HPLC-MS/MS.

A modified QuEChERS protocol, coupled to HPLC-MS/MS, was used for the analysis of 102 pesticides in green teas produced in Jiangxi province, China. For accurate quantification, matrix-matched calibration curves were applied to compensate for matrix effects. Recoveries for these pesticides ranged from 62% to 125% with relative standard deviations (RSDs) lower than 18%. The limits of detection and quantification ranged from 0.03 to 15 µg/kg and 0.1 to 50 µg/kg, respectively. We determined that 67% of green tea samples contained some pesticide residues and most contained more than five pesticides. Moreover, the levels of 11 pesticide residues in 18 samples were found to be greater than the values permitted in EC Regulation No. 396/2005.