Organic Solvent-Saving Sample Preparation for Systematic Residue Analysis of Neonicotinoid Insecticides in Agricultural Products Using Liquid Chromatography-Diode Array Detection

A sample preparation method using lower amounts of organic solvents has been established for seven neonicotinoid insecticides (acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam) in cucumber, eggplant, and spinach samples with conventional high-performance liquid chromatography-diode array detector (HPLC-DAD). After extraction method used in QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) (extraction with acetonitrile, and phase separation and dehydration of acetonitrile phase), the crude sample extracts were cleaned up with solid-phase extraction using graphitized carbon black and silica gel modified with ethylene diamine-N-propyl moiety (primary-secondary amine). The amount of organic solvents required before determination was only about 17 mL per sample. The matrix interference derived from samples was compensated using matrix-matched calibration. Average recoveries of the seven analytes were 83-100 %, with relative standard deviation of less than 10 %. The correlation coefficients were greater than 0.999 over the range between 0.01 and 0.5 mg kg(-1). The limit of quantification for each analyte was 0.002-0.037 mg kg(-1). This systematic residue analytical method using HPLC-DAD was applied successfully to neonicotinoid insecticide-incurred vegetable samples.