Rapid Extraction of Imidacloprid in Tomatoes by Ultrasonic Dispersion Liquid–Liquid Microextraction Coupled with LC Determination

A simple method for the extraction and determination of trace imidacloprid in tomatoes was developed using ultrasonic dispersion liquid–liquid microextraction coupled with liquid chromatographic separation. An ultrasonic dispersion process was applied to accelerate the formation of the fine cloudy solution without using disperser solvents, which was markedly increased the extraction efficiency and reduced the equilibrium time. The results revealed that tetrachloroethane as extraction solvent could be directly applied to the filtered tomato juice with the assistance of ultrasonic dispersion. Under the optimum condition, the enrichment factor of imidacloprid could reach 375 folds and the average recovery of samples ranged from 87.6 to 110% with RSD less than 4.5% (n = 3). Compared to the conventional sample pretreatment method, the proposed method had the advantage of short time, simple operation, high sensitivity and low consumption of organic solvent.