Simultaneous determination of three neonicotinoid insecticide residues and their metabolite in cucumbers and soil by QuEChERS clean up and liquid chromatography with diode-array detection†
A new sensitive, selective and validated HPLC-DAD method was developed for the simultaneous determination of three neonicotinoid insecticides named dinotefuran, thiamethoxam and Clothianidin with their metabolite 1-methyl-3-nitroguanidine in cucumbers and soil based on QuEChERS as a pretreatment procedure. In the QuEChERS procedure, cucumber samples were extracted with acetonitrile and cleaned using C18, while soil samples were extracted with a mixture of acetonitrile : dichloromethane (1 : 2). The HPLC conditions were optimized where the neonicotinoids were separated using a gradient elution of water : acetonitrile and a Synergy Hydro RP C18 column. Matrix matched calibration standards were prepared in cucumbers and soil to eliminate the interference of the matrix. Relative standard deviations (RSDs) were less than 2.08% for all of the recovery tests. The limits of detection (LODs) and quantification (LOQs) for the neonicotinoids were in the ranges of 0.01–0.08 μg g−1 and 0.03–0.24 μg g−1, respectively. The method was applied successfully to determine residues and rates of disappearance of the three neonicotinoids from cucumbers and soil and their half lives.