Preparation Of Molecularly Imprinted Monolithic Columns And Applications In Chiral Separation

The molecularly imprinted monolithic columns, which combine the high stereoselectivity of molecularly imprinted polymers with the advantages of good hydrodynamic characteristic, low flow resistance as well as easy preparation of monolithic materials, have potential applications in chiral separation.The proper in-situ polymerization systems of acidic and basic compounds using amino acid derivatives and cinchona alkaloids as template molecules respectively were adopted for preparation of molecularly imprinted monolithic columns by systematically investigating the effect of polymerization conditions on pore structure and selectivity of resulting polymers. The enantiomers of amino acid derivatives and the diastereomers of cinchona alkaloids were successfully resolved on these columns. The effects of the content of acetic acid in mobile phase, temperature and flow rate on the separation were investigated and the recognition performance in aqueous media and cross-reactivity of the molecularly imprinted monolithic columns were also studied.A molecularly imprinted monolithic disk with dimension of 10 X16 mm i.d. was prepared. It showed a very low flow resistance and similar separation performance with that of the long column. Rapid chiral separations were achieved on it by combining high flow rate with gradient elution.A cinchonine imprinted monolithic polymer was directly prepared in a fused capillary column by in-situ polymerization. Large flow-through pores were present in the monolithic rod by scanning electron microscopy. Diastereomers of cinchonine and cinchonidine were separated in pressure-assisted capillary electrochromatography mode, and the resulted separation efficiency was much higher than that obtained in high performance liquid chromatography. A rapid separation of cinchonine and cinchonidine was obtained under optimizing conditions.The nitrophenol and hydroxybenzoic acid isomers imprinted monolithic columns were prepared by in-situ polymerization. The different recognition ability to template molecules was observed on these polymers. It was found that the structure andacidity of template molecules should be responsible for the discrepant recognition, which influence the formation and strength of interaction between template molecule and functional monomer in imprinting process.The thermodynamic and kinetic in the chiral separation process on the molecularly imprinted monolithic column were studied. The thermodynamic parameters in the separation of enantiomers of amino acid derivatives and diastereomers of cinchona alkaloids were calculated and the dissociation constants of cinchonine and cinchonidine on the cinchonine imprinted monolithic disk were determined by frontal analysis.