Representative Commodity for Six Leafy Vegetables Based on the Determination of Six Pesticide Residues by Gas Chromatography

A residue analytical method was developed for the determination of trichlorfon, chlorpyrifos, dimethoate, beta cypermethrin, deltamethrin, and chlorothalonilin in six leafy vegetables by gas chromatography-electron capture detector (GC-ECD) and gas chromatography-flame photometric detector (GC-FPD). The method had a good linearity (R-2 >= 0.9924) and precision (RSD <= 14.0%). The limits of quantification (LOQ) of six pesticides were all 0.01 mg/kg. Average recoveries of six pesticides ranged from 81% to 119%. The developed method was successfully applied to study the initial deposits, degrade characteristics, and terminal residues for six pesticides applied to six leafy vegetables under the same dose of formulation. The half-life of six pesticides was in the range of 0.8-8.8 days. The highest initial deposits, maximal residues, and terminal residues were found on leaf mustard and sweet potato leaves as the same pesticides were applied in different crops. Therefore, leaf mustard can be selected as representative commodity in the same subgroup to realize the residual extrapolation. This conclusion should be considered as a complement on crop classification of China.