Multiresidue Analysis of Five Neonicotinoid Insecticides and Their Primary Metabolite in Cucumbers and Soil Using High-Performance Liquid Chromatography with Diode-Array Detection.

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, in cucumbers 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 calibration standards 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.