Dispersive graphene-based silica coated magnetic nanoparticles as a new adsorbent for preconcentration of chlorinated pesticides from environmental water

The present study describes the synthesis, characterization and application of new graphene-based silica coated magnetic nanoparticles (Fe3O4@SiO2-G) for the simultaneous preconcentration of four chlorinated pesticides namely lindane, chlorpyrifos, hexaconazole and azaconazole from contaminated water. The newly synthesised adsorbent was characterized using FT-IR spectroscopy, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). Chlorinated pesticide extraction efficiency of the Fe3O4@SiO2-G was evaluated through magnetic solid phase extraction (MSPE) using gas chromatography with a micro electron capture detector (GC-mu ECD). Experimental parameters, i.e., desorption solvent, solvent volume, extraction time, desorption time, sample volume, adsorbent dosage and solution pH were optimized. Compared to commercial C18 sorbent and Fe3O4@SiO2, the newly synthesized Fe3O4@SiO2-G adsorbent showed a linear response (1-100 pg mL(-1)), low limits of detection (0.12-0.28 pg mL(-1)) and high adsorption capacity (13.04-18.69 mg g(-1)) with a coefficient of determination (R-2) of 0.999. Environmental water samples were used to assess the field applicability of the adsorbents. Excellent percent recovery (80.8-106.3%) was achieved for Fe3O4@SiO2-G at pH 6.5. The results showed that the newly synthesized Fe3O4@SiO2-G is an efficient adsorbent with good potential for the preconcentration of selected chlorinated pesticides from aqueous media.