Determination of Seven Neonicotinoid Insecticides in Cucumber and Eggplant by Water-Based Extraction and High-Performance Liquid Chromatography

An environmentally friendly water-based extraction method combined with conventional high-performance liquid chromatography with diode array detection is reported for the determination of seven hydrophilic neonicotinoid insecticides (dinotefuran, nitenpyram, thiamethoxam, clothianidin, imidacloprid, acetamiprid, and thiacloprid) in two fruiting vegetables (cucumber and eggplant). Insecticides were extracted from the vegetables with water and were preconcentrated with two solid-phase extraction cartridges packed with polymeric adsorbent, graphitized carbon black, and aminopropyl-modified silica gel. Matrix interferences were investigated. In order to accurately determine nitenpyram in cucumber and all neonicotinoids in eggplant, a matrix-matched calibration method was required. Average recovery values from the fortified samples were between 82% and 114%, with relative standard deviations less than 10%. The limits of quantification were 0.007–0.017 µg g−1 in cucumber and 0.003–0.019 µg g−1 in eggplant. The results demonstrate that the organic solvent-saving sample preparation method is useful for the extraction of hydrophilic neonicotinoids from vegetables with high water content.