Analysis of Organophosphorus Pesticides by HPLC Using Magnetic SPE with Nitrogen-Doped Reduced Graphene Oxide/Fe3O4 Nanocomposite as the Adsorbent

In this study, a method was developed for extraction and preconcentration of trace amounts of organophosphorus pesticides (OPPs), including fenitrothion, chlorpyrifos-methyl, and chlorpyrifos in environmental water. The method uses a new magnetic solid-phase extraction technique, followed by high performance liquid chromatography (HPLC) with ultraviolet (UV) detection. Nitrogen-doped reduced graphene oxide-iron oxide (Fe3O4) nanocomposite, used as the adsorbent of organophosphorus pesticides, was successfully prepared using an easy hydrolysis process. The nanocomposite was synthesized and characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD). The effects of type and ratio of eluents, amount of the graphene oxide (GO)/Fe3O4 nanocomposite, pH, ionic strength, equilibrium time, and ultrasound time on the quantitative recoveries of fenitrothion, chlorpyrifos-methyl, and chlorpyrifos were investigated. On the basis of the best condition, the recoveries of the target analytes in real water samples were between 84.40% and 105.05%. The relative standard deviations varied from 1.21% to 4.22%. Finally, the method was successfully applied to the determination of three organophosphorus pesticides in real environmental water samples.