Optimization of high-performance liquid chromatography and solid-phase extraction for determination of organophosphorus pesticide residues in environmental samples

High-performance liquid chromatography with solid-phase extraction (HPLC-SPE) was optimized for the analysis of three organophosphorus pesticide residues in water, apples and vegetable samples. Octadecylsilica disks (47-mm diameter) were used for solid-phase extraction. The parameters that affect both separation and extraction of methyl parathion, parathion and phoxim, such as mobile-phase composition, ionic strength, temperature, pH, and breakthrough volume, were investigated. The application of optimized HPLC-SPE to environmental samples gave reproducible results with low detection limits of 5 µg L^?1 for methyl parathion and parathion and 2.5 µgL^?1. Precisions of less than 8, 9 and 12% were obtained for water, spinach and apple samples, respectively.