[Single-laboratory Validation Study of an Improved Multi-residue Method for Pesticide Residues in Green Tea Leaves...

In this study, a multi-residue method for pesticide residues in green tea leaves was developed using LC-MS/MS and the validity of the developed method was evaluated in accordance with Japanese guidelines. Based on the previously reported method, the amount of acetonitrile used for extraction, amount of hexane-washed distilled water added to the sample, and solid-phase column used for purification were investigated. In the developed method, the pesticides were extracted with 25 mL of acetonitrile after adding 10 mL of the hexane-washed distilled water to the sample and salted out. By cleaning the acetonitrile layer using Inert Sep^® PLS-3 (200 mg/20 mL) and Supelclean^TMENVI-Carb^TMII/PSA (300 mg, 600 mg/6 mL), the effect of the matrix on the green tea leaves was reduced. This method was validated by performing recovery tests at two concentrations (0.01 and 0.1 mg/kg) of 92 pesticides. Of the 92 pesticides, 84 met the criteria. The limit of quantification was 0.01 mg/kg, which is the uniform limit specified by the Food Sanitation Law of Japan. This study presents that the developed method is useful for the analysis of pesticide residues in green tea leaves.