A sensitive, selective, and validated HPLC–diode-array detection method was developed for the simultaneous determination of five neonicotinoid insecticides—acetamiprid, imidacloprid, nitenpyram, flonicamid, and thiacloprid—and their primary metabolite, 6-chloronicotinic acid, incucumbers and soil based on the quick, easy, cheap, effective, rugged, and safe (QuEChERS) technique as a pretreatment procedure. In the QuEChERS procedure, cucumber samples were extracted with acetonitrile and cleaned using C18, whereas soil samples were extracted with an acetonitrile–dichloromethane mixture (1 + 2). The HPLC conditions were optimized by separating neonicotinoids using an acetonitrile–water mixture (25 + 75) and a Synergi Hydro RP C18 column. Matrix-matched calibrationstandards were prepared in cucumber and soil to eliminate any matrix interference. RSDs were ≤9% in all recovery tests. LODs and LOQs for the five neonicotinoids were in the ranges of 0.006–0.122 and 0.018–0.366 μg/g, respectively. This method was successfully applied to determine residues, the rate of disappearance of the five neonicotinoids from cucumber and soil, and the half-lives of the neonicotinoids.

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.