Determination of Chlorpyrifos in Rice Based on Magnetic Molecularly Imprinted Polymers Coupled with High-Performance Liquid Chromatography

The magnetic molecularly imprinted polymers (MMIPs) were prepared and used for the selective separation of chlorpyrifos from rice samples. The MMIPs were synthesized by surface-imprinted polymerization, using functionalized Fe3O4 particles as magnetic cores, chlorpyrifos as template, methacrylic acid as functional monomer, and trimethylolpropane trimethacrylate as cross-linker. Magnetic particles were characterized by scanning electron microscopy, Fourier-transform infrared spectrometry, physical property measurement system, and thermogravimetric analyzer. Adsorption studies were carried out to investigate the specific binding capacity, kinetics, and recognition specificity. The kinetic property of MMIPs was well fitted to the pseudo-second-order equation. The selective recognition experiment demonstrated that MMIPs had high selectivity towards chlorpyrifos over reference compound. Chlorpyrifos extracted from the rice samples was purified with MMIPs and detected by high-performance liquid chromatography. Under the optimal conditions, the detection limit of chlorpyrifos was 0.0072 mu g g(-1). The relative standard deviations of intra- and interday ranging from 2.4 to 4.6 % and from 3.5 % to 7.3 % were obtained, respectively. The recoveries of chlorpyrifos at three different fortified concentrations (0.025, 2.5, and 5 mu g g(-1)) were in the range of 81.2-92.1 %.