Preparation And Application Of Selective Adsorption Materials For Pesticide And Veterinary Drug Residues In Food

Sample pretreatment is the most important part in the process of detection of pesticide and veterinary drug residues,it is of great significance to study the new type of substituteable,small sample demand,efficient and practical pretreatment materials to improve the efficiency of traditional pretreatment methods,and then improve the accuracy of subsequent instrument detection.Therefore,in this work,the molecular imprinting technique was applied to solid phase microextraction,solid phase extraction,and combined with high performance liquid chromatography to establish the analysis method of trace tetracycline antibiotics and sulfonylurea herbicides in food.The main contents are as follows:?1?A newly hydrophilic tetracycline imprinted solid phase microextraction fiber using methacrylic acid and 2-hydroxyethyl methacrylate as a bifunctional monomer and stainless-steel wire as carrier was prepared by improved multiple co-polymerization method.The developed molecularly imprinted polymer coated solid phase micro-extraction fibers were characterized through scanning electron microscope,Fourier transform infrared spectrometry and thermogravimetry analysis.The adsorption performance of fiber coatings were analyzed by adsorption isotherms,hydrophilicity adsorption,selectivity experiments and further studied by adsorption model.The fiber with cross-linked and porous structure was observed and high thermal and chemical stability.The maximum adsorption capacity of this fiber with good selectivity reached2.35?g/mg in aqueous matrices,the imprinting factor was 1.78 and selectivity coefficient for structural analogs and competitive substances was 1.39?9.55.Under the optimized solid phase microextraction conditions,our home-made solid phase microextraction fiber directly combinded with HPLC has been successfully developed for simultaneous monitoring of tetracyclines in food samples.A satisfactory detection limits?0.38?g/kg?0.72?g/kg,S/N=3?and good recoveries?77.33%?104.45%?were obtained by adding tetracycline,oxytetracycline at three levels to milk,chicken and fish samples.Additionally,this kind of hydrophilic solid phase microextraction fiber can effectively eliminate matrix interference and reduce organic solvent pollution.?2?Based on the self-polymerization of dopamine in weak alkaline solution and superadhesive properties on various materials surface,a novel and highly selective magnetic molecularly imprinted polymer for chlorosulfuron?CS?detection were prepared on the surface of graphene oxide/Fe₃O₄ nanoparticles using CS as a template.The morphology and structure of the resultant imprinted nanoparticles?MGO@PDA-MIPs?were characterized by transmission electron microscopy,Fourier transform infrared spectrometry,nitrogen adsorption–desorption,vibrating sample magnetometry,X-ray diffraction and thermogravimetry analysis.The adsorption performance of polymers was investigated by adsorption kinetics,equilibrium binding,selectivity experiments and further studied by adsorption model.The results demon-strated that the synthesized polymer possess excellent selectivity toward CS with high imprinting factor of 3.41 compared with non-imprinted polymer,and rapidly achieve adsorption equilibrium and efficient desorption,the selectivity coefficient is 2.38?11.65.Under the optimized conditions,a method was set up based on MGO@PDA-MIPs magnetic solid phase extraction coupled to HPLC for the determination of sulfonylurea residues in cereal samples,the detection limit was 1.61?g/kg?1.95?g/kg and recovery rate was 80.65%?101.01%.Moreover,the MGO@PDA-MIPs can be re-used for at least 7 times.