Montmorillonite reinforced polyaniline/polyamide nanocomposite as a novel coating for stir bar sorptive extraction of organophosphorous pesticides in fruit juices and vegetables

In this research a novel nanocomposite based on incorporation of montmorillonite (MMT) [1,2] into polyaniline-polyamide (PA) hybrid was prepared by in situ oxidative polymerization of polyaniline (PANI) into MMT/PA mixture and subsequently solvent exchange method to obtain a thin layer onto stir bar substrate. The morphology and surface characteristic of PA and MMT/PANI/PA coated stir bars were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscomy (EDX), X-ray diffraction (XRD) and Fourier transform infrared sepectroscopy (FTIR). The prepared MMT/PANI/PA nanocomposite-based stir bar was applied as an extraction device for stir bar sorptive extraction (SBSE) [3] of organophosphorous pesticides (OPPs) in some fruit juices and vegetables in combination with gas chromatography-flame ionization detector (GC-FID) detection. The effect of MMT amount in the nanocomposite and also the effect of PANI incorporation into PA on the extraction capability of the coating was investigated. Important factors influencing the extraction and desorption processes including extraction time, salt content, pH, desorption solvent, its volume and desorption time were studied and optimized using response surface methodology (RSM) applying central composite design (CCD) [4]. Limit of detection (LOD) and linear dynamic range (LDR) of the method were in the range of 0.2 to 1 ng mL−1 and 0.6-1000 and 3-1000 ng mL-1, respectively. The method precision (RSD %) with four replicates determinations was in the range of 2.5 to 4.4 % for distilled water at the concentration level of 100 ng mL−1. The developed method was successfully applied to the various fruit juices and vegetable samples, while the relative recoveries (RR%) were obtained to be in the range of 80.0 to 99.7%.