Determination of Organophosphorus Pesticide Residues in Vegetables by Electrokinetic Sequential Injection Analysis

A fast and convenient analysis method based on a plant esterase reaction inhibited by organophosphorus pesticides was developed for the determination of the pesticide residues in vegetable samples. The proposed method was performed with an electrokinetic sequential injection analysis (ESIA) system, which consisted of a spectrophotometer, a homemade electro‐osmosis pump, and four solenoid valves controlled by a Visual C program. The plant esterase extracted from fresh flour was adopted in the enzyme reaction. Several reaction parameters, such as the sample volume, the length of reaction coil, and the concentrations of reactants, are discussed in detail. The linear range of the calibration concentration was 0.03–0.5 µg/g dimethoate, which was used as a converted concentration of total organophosphorus pesticides. The detection limit of 0.01 µg/g dimethoate was achieved. The analytical throughput of the proposed method was about 24 samples per hour.