Preparation Of Surface Molecularly Imprinted Polymers And Their Applications In Analysis

High selectively separation and analysis of target substance in complex matrix is the necessary step to study the composition and structure of the material,along with the interaction between different substances.Therefore,the development of new analytical methods for separation from a complex sample matrix is of great significance.Molecularly imprinted polymers?MIPs?are synthetic biomimetic materials with target molecule specific interaction.Due to their good stability,easy preparation,low cost and other advantages,MIPs have been widely used in the fields of separation,sensing,catalysis,drug delivery and so on.Based on molecular imprinting technology,the preparation of core-shell magnetic surface imprinting materials and their analytical application in complex sample matrix were studied in this paper.The main research are as follows:1.For the detection of pesticide residues in complex biological samples,2,4-dichlorophenoxyacetic acid?2,4-D?was chosen as the template molecule.By using surface initiated-reversible addition-fragmentation chain transfer?si-RAFT?polymerization,superparamagnetic core-shell Fe₃O₄@MIPs nanoparticles were constructed with well morphology and uniform thickness.The Fe₃O₄@MIPs nanoparticles were characterized by using transmission electron microscopy,infrared absorption spectroscopy,vibrating sample magnetometer,thermogravimetric analysis,X-ray photoelectron spectroscopy and X-ray diffraction.Based on the active/controlled polymerization of RAFT,the molecularly imprinted polymer shell with uniform morphology and uniform thickness was successfully constructed on the magnetic Fe₃O₄@SiO₂ surface.Through the isothermal adsorption experiment,the adsorption kinetics and selectivity experiments,the selectively adsorption properties of Fe₃O₄@MIPs were investigated.The results showed that the prepared Fe₃O₄@MIP material showed specific recognition ability for 2,4-D,but no response to its structural analogues.The prepared Fe₃O₄@MIP had the characteristics of high selectivity,quick identification and easy magnetic manipulation,and had been applied in the selective enrichment of 2,4-D from tap water and vegetable samples.2.For the recognition of biological macromolecule such as peptides and proteins,surface imprinting strategy with orientation control based on hydrazine bond was constructed.By using leucine enkephalin as the template molecule,which was grafted on the surface of the magnetic microspheres by p H sensitive hydrazone bond,and then through the way of constructing polymer shell by the self-polymerization of dopamine,the imprinting sites were orderly distributed on the polymer surface.The elution of the template molecule could be obtained by using the characteristic of pH responsive fracture of hydrazone bond.Through the transmission electron microscope,the MIP shell was thin and uniform,which was beneficial for the distribution of the imprinting sites on their surface.The experimental conditions of polymerization and adsorption were further optimized to achieve satisfactory selective recognition performance.This method was expected to be applied in the field of detection of enkephalin in human body fluid,and could be extended to the specific recognition of protein.3.For the problem of the separation of specific substances in natural products,tea saponin in Camellia fruit was chosen as the target molecule.Unlike the method of choosing the target molecule as the template molecule in traditional ways,glycyrrhizic acid,which had similar parts of structure with tea saponin,was used as the template molecule to overcome the draw back of uncertained structures of tea saponin.By combining with surface imprinting technique,core-shell magnetic molecularly imprinted polymer was prepared with Fe₃O₄ as the core.Then a series of experiments was in progress to optimize the polymerization conditions.A preliminary study of the Fe₃O₄@MIP showed the ability of selective separation,which will be applicable to the selective enrichment of tea saponin from the extract of Camellia fruit.