Study On Preparation Of Molecular Imprinting Polymer Microspheres And Application Of Chitosan In Chiral Separation By Capillary Electrophoresis

Molecular imprinting is a versatile and facile method for preparing synthetic polymers with predetermined molecular recognition properties.It can be employed in a variety of applications,such as chromatography separations,solid extractions, sensors,membrane separation and so on.In the first part of this study,molecular imprinting polymer microspheres with 4-aminoantipyrine(4-AP) as template were prepared by precipitation polymerization. The mixtures of dodecanol and toluene,methacrylic acid,ethylene glycol dimethacrylate were used as solvent,functional monomer,cross linker,respectively. The ability of the polymers to rebind 4-AP specifically in aqueous solutions was assessed.A best adsorption behavior and molecular selectivity occurred when 15mL solvent with 10%toluene was used and the concentrations of template,functional monomer,cross linker as well as initiator were 0.02mol/L,0.1mol/L,0.4mol/L, 0.002mol/L,respectively.The separation factor was up to 3.72 when antipyrine was used as the competing molecule.Scatchard analysis showed that the MIPs recognized 4-AP with two classes of binding sites.The dissociation constants and the maximum apparent binding capacities were K_d=3.89μg/mL,Q_max=49.99μg/mg for high affinity binding site and K_d=84.03μg/mL,Q_max=11.69μg/mg for low affinity binding site.In the second part of this study,chitosan,a cationic natural polymer,was employed as a chiral additive selector for enantioseparation of DL-tryptophan in capillary electrophoresis.The effects of several parameters on the ability of separation were studied.A best separation of tryptophan enantiomers was achieved by using 5mmol/L NaAc,0.02%(w/v) chitosan and 1.5mmol/L Cu²⁺ while the pH of the buffer was 3.5.The separation factor was 1.87 and the resolution was 1.02.The performance reproducibility was good.