Determination of Methomyl in Vegetables by Magnetic Molecularly Imprinted Polymer Extraction/High Performance Liquid Chromatography

KeyWord:magnetic molecularly imprinted polymer  methomyl  vegetable  high performance liquid chromatography

Abstract:

      A rapid and selective method was successfully developed using magnetic molecularly imprinted polymer£¨MMIP£© as sorbent for the extraction of methomyl from vegetable samples.The MMIP was synthesized using methomyl as template molecule£¬methacrylic acid as functional monomer£¬ethylene glycol dimethacrylate as crosslinking agent and Fe3O4 magnetite as magnetic component.The MMIP was characterized by Fourier transform infrared spectra£¬scanning electron microscope and physical property measurement system.Scatchard plot analysis revealed that two kinds of different binding sites existed in MMIP,in which the maximum amount of apparent binding and dissociation constant of binding sites were as follows:Qmax1=0.053 04 mmol/g£¬Kd1=0.314 35 mmol/L;Qmax2=0.130 51 mmol/g£¬Kd2=1.921 22 mmol/L.The kinetic property of MMIP was well fitted to the pseudo-second-order equation.The result indicated that MMIP had high selectivity towards methomyl over reference compound.The effects of extraction solvent£¬MMIP amount£¬extraction time£¬shaking rate£¬desorption solvent on recoveries of methomyl were investigated.Under the optimal conditions£¬the limit of detection of methomyl was 0.012 mg/kg£¬the spiked recoveries of methomyl were in the range of 86%-94% with relative standard deviations£¨RSDs£© of 2.2%-6.1%.The method was applied in the determination of methomyl in vegetable samples£¬including cabbage£¬pakchoi£¬tomato£¬cucumber and pepper£¬in which£¬methomyl was detected in the tomato sample with concentration of 1.135 mg/kg.Compared with the traditional method£¬the proposed method is rapid and effective£¬and is promising for the analysis of pesticide residues in food samples.