Study Of Molecularly Imprinted Membrane For Efficient Chiral Resolution Of Amino Acids

The two isomers of chiral drug usually have different pharmacology and therapy fuctions, whereas it is the most difficult system in separation field because their similar chemical and physical properties, so it is the obvious importance in both science and application to achieve optical resolution and gain the pure isomer. Molecularly imprinted membranes (MIMs), which combine the advantages of molecular imprinting and membrane technology, will potentially become novel separation media for the recognition and separation of chiral substances. In this work, novel organic-inorganic hybrid molecular imprinted membrane was prepared and it was realized in aqueous solution to efficiently separate isomeric compound and structure analogs of amino acids.MIMs were prepared using D-phenylalanine (D-Phe) as template, sodium alginate (SA) with large numbers of carboxyl groups and hydroxyl groups as a multifunctional polymer and bulk membrane matrix. Firstly, molecularly imprinted and control SA membranes were prepared by phase conversion method together with aqueous sulfuric acid treatment or glutaraldehyde corsslink. The chemical composition, structure and morphology of the alginic acid membranes were obtained by FT-IR,SEM and contact angle. The effect of multifunctional polymer content, template content, methanol concentration in feed and heat-treatment temperature on the ability of membranes for chiral resolution of D, L-Phe aqueous mixtures were investigated. The most optimized separation factors were 1.32 and 1.47 of SA-H(D) and SA-GA(D) membrane, respectively. The enantioselectivity of the membranes crosslinked by glutaraldehyde were better than those by sulfuric acid treatment.Secondly, D-Phe molecularly imprinted and control sodium alginate and 3-Aminopropyl-triethoxysilane (SA-APTES) hybrid membranes were prepared by a simple sol-gel process in aqueous system. The chemical composition, physical structure and mechanical performance of the hybrid membranes were characterized by FT-IR, SEM-EDX and mechanical stress-strain test. The binding capacity and selectivity of the membranes were obtained by binding experiments. The effects of APTES content, template content, feed concentration and heat-treatment temperature on the chiral resolution ability of the membranes were investigated. The results indicated that molecularly imprinted SA-APTES hybrid membranes showed obvious improved specific adsorption selectivity towards templates compared with control membranes, and the adsorption isotherm was accorded with Langmuir isothermal adsorption. The transport of D- phenylanaline through MIMs fit the mechanism of"preferential sorption, preferential permeation", and there was only a kind of bonding locus analysised by Scatchard. The maximum separation factor achieved in this study was about 2.87.Finally, D-Phe and D-Tyrison were separated by D-Phe molecularly imprinted and control SA-APTES hybrid membranes in aqueous system. The effects of APTES content and heat-treatment temperature on the separation ability of the membranes were investigated. D-Phe and D-Tyrison were effectively separated by D-Phe molecularly imprinted SA-APTES hybrid membranes, and the maximum separation factor achieved in this study was about 2.86.