Graphene Oxide/Polyamide Nanocomposite as a Novel Stir Bar Coating for Sorptive Extraction of Organophosphorous Pesticides in Fruit Juice and Vegetable Samples

In this research, a novel nanocomposite based on incorporation of graphene oxide (GO) into polyamide (PA) was prepared by solvent blending method and subsequently it was coated on stir bar substrate through solvent exchange method. The morphology and surface characteristic of PA- and GO/PA-coated stir bars were investigated using scanning electron microscopy (SEM). The prepared GO/PA nanocomposite-based stir bar was applied as an extraction device for stir bar sorptive extraction (SBSE) of organophosphorous pesticides (OPPs) including chlorpyrifos, ethion, and phosalone in fruit juice and vegetable samples followed by gas chromatography-flame ionization detector (GC-FID) detection. The effect of GO doping level into the nanocomposite on the extraction capability of the coating was investigated. Important factors influencing the extraction and desorption processes including extraction time, salt content, sample volume, pH, desorption solvent, its volume, and desorption time were studied and optimized applying central composite design (CCD). Limits of detection (LOD) and linear dynamic ranges of the method were in the range of 0.3-1 ng mL(-1) and 1-1000 and 3-1000 ng mL(-1), respectively. The method precision (RSD%) with four replicate determinations was in the range of 6.2-9.1% for distilled water at the concentration level of 100 ng mL(-1). The developed method was successfully applied to various fruit juices and vegetable samples, while the relative recoveries (RR %) were found to be in the range of 82.0-95.6%.