Preparation And Recognition Property Of Molecularly Imprinted Materials On Hydroxybenzoic Acids

Abstract:The principle of molecular impringting (MIP), composition, preparation methods, properties and applications of MIP were summarized. Hydroxybenzoic acids molecularly imprinting materials and their properties were investigated and their adsorption performances were studied. Various magnetic molecularly imprinting materials were prepared and used for analyzing some actual samples. The main contens are as follows:(1) Novel magnetic molecularly imprinted polymers (MMIPs) based on4-hydroxy-benzoic acid (4-HBA) as template have been successfully developed to selectively and simultaneously extract and determine five hydroxybenzoic acids in aqueous solution. Various parameters affecting adsorption/desorption behavior are evaluated for achieving optimal recovery. Under optimum conditions, adsorption process follows Langumuir adsorption isotherm and pseudo-second-order reaction kinetics. Thermodynamic parameters reveal that adsorption process is spontaneous, endothermic and entropy driven one. Both MMIPs show high adsorption capacity, good selectivity, rapid kinetic binding, favorable reproducibility and stability. Spiked recoveries of five hydroxybenzoic acids on MMIPs range from83%to102%with RSD less than6.9%. Results demonstrate that MMIPs could be reliably applied to direct extraction and determination of hydroxybenzoic acids from real aqueous solution.(2)Molecular imprinted polymers over magnetic mesoporous silica microspheres (Fe3O4@mSiO2@MIPs) have firstly been prepared to understand and characterize the mechanism of selective recognition of protocatechuic acid (PCA) with high capacity and fast binding. The resulting Fe3O4@mSiO2@MIPs were characterized by TEM、FT-IR、 TGA、BET and VSM. The adsorption process between PCA and Fe3O4@mSiO2@MIPs followed Langumuir adsorption isotherm with maximum adsorption capacity17.2mg/g and pseudo-second-order reaction kinetics. Compare with MIPs over magnetic silica microspheres (Fe3O4@SiO2@MIPs, maximum adsorption capacity7.5mg/g), Fe3O4@SiO2@MIPs had higher adsorption capacity for its large surface area and enough recognition sites on the internal and external surface of mesopore channels. Subsequently, Fe3O4@mSiO2@MIPs were successfully applied for selective enrichment and determination of trace PCA from Syzygium aromaticum. The results indicated that we combine three advantages into Fe3O4@mSiO2@MIPs (magnetic core for quick separation, mesoporous silica layer for enough recognition sites, and surface imprinting for fast binding and excellent selectivity) for efficient and selective extraction of PCA from complex natural product.(3) Molecular imprinted polymers over magnetic silica microspheres (Fe3O4@SiO2@mSiO2@MIPs) have firstly been prepared to understand and selective recognition of gallic acid (GA) form various kinds of fruit juice. Inspired by the self-polymerization of dopamine, we synthesized a polydopamine-based molecular imprinted film coating on Fe3O4@SiO2@mSiO2-The results show that sorbent materials in aqueous solution with high adsorption capacity and adsorption rate rapidly. The resulting Fe3O4@SiO2@mSiO2@MIPs were characterized by TEM、 FT-IR、 TGA and VSM. After six consecutive adsorption-desorption cycles, the efficiency of adsorption was still as high as95.2%of the first one. The results manifested that Fe3O4@SiO2@mSiO2@MIPs were stable and reusable.