Water-Based Extraction and Liquid Chromatography–Tandem Mass Spectrometry Analysis of Neonicotinoid Insecticides and Their Metabolites in Green Pepper/Tomato Samples

This paper proposes an environmentally friendly method involving water-based extraction of the samples, cleanup of the extracts by solid-phase extraction, and subsequent liquid chromatography coupled with tandem mass spectrometry, which was used for simultaneous determination of seven hydrophilic neonicotinoid insecticides as well as their metabolites in agricultural samples. The effects of sample matrix on detection of the target compounds were negligibly small. Mean recoveries obtained at spiked concentrations between 0.01 and 1.00 mg/kg were 71.2–122.3% with relative standard deviations of ≤7.5%. When the method was applied to crop samples sprayed with commercial formulations of the target compounds, the residual concentrations of the compounds determined by the proposed method (0.015–0.27 mg/kg in green peppers and 0.017–0.31 mg/kg in tomatoes) were equivalent to those determined by the official Japanese method (0.017–0.26 mg/kg in green peppers and 0.013–0.30 mg/kg in tomatoes)