Dispersive solid-phase extraction of organophosphorus pesticides from apple, cucumber and water samples using reduced graphene oxide coated with ZnO nanocomposites as a sorbent

Abstract

In this work, reduced graphene oxide coated with ZnO (RGO–ZnO) nanocomposites was synthesized by a hydrothermal reduction strategy. The presence of ZnO was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Subsequently, RGO–ZnO was used as a dispersive solid-phase extraction (DSPE) sorbent for the enrichment of eight organophosphorus pesticides (OPs) in apple, cucumber and water samples prior to their determination by gas chromatography-mass spectrometry (GC-MS). Several experimental parameters affecting the extraction efficiencies, including the amount of RGO–ZnO, extraction time, and the pH of the sample solution, as well as the type and volume of eluent solvent, were investigated and optimized in this work. Under the optimal experimental conditions, good linearity existed in the range of 0.5–200.0 ng g⁻¹ for all the analytes with the correlation coefficients (R²) ranging from 0.9894 to 0.9983. The limits of detection (S/N = 3) of the method for the compounds were between 0.01 and 0.05 ng g⁻¹. Good reproducibilities were acquired with the relative standard deviations (RSDs) below 8.6% for both intra-day and inter-day precision. The recoveries of the method were in the range of 75.0% to 104.2%.