Magnetic graphene coated inorganic-organic hybrid nanocomposite for enhanced preconcentration of selected pesticides in tomato and grape.

The new magnetic graphene based hybrid silica-N-[3-(trimethoxysilyl)propyl]ethylenediamine (MG@SiO-TMSPED) nanocomposite was synthesized via sol-gel process, and used as an effective adsorbent in magnetic solid phase extraction (MSPE) of three selected pesticides followed by gas chromatography micro-electron capture detection (GC-μECD). The adsorbent was characterized using Fourier transform-infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET), Barrett-Joyner-Halenda (BJH), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDXS) techniques. The analytical validity of the developed method was evaluated under optimized conditions and the following figures of merit were obtained: linearity, 1-20μgkg with good determination coefficients (R=0.995-0.999); limits of detection (LODs), 0.23-0.30μgkg (3×SD/m, n=3); and limits of quantitation (LOQ), 0.76-1.0μgkg (10×SD/m, n=3). The precision (RSD%) of the proposed MSPE method was studied based on intra-day (3.43-8.83%, n=3) and inter-day (6.68-8.37%, n=12) precisions. Finally, the adsorbent was applied to determination of pesticides in tomato and grape samples and good recoveries were obtained in the range from 82 to 113% (RSDs 5.1-8.1%, n=3).