Enantioselective Recognition Of Amino Acids Based On Molec-ul Arly Imprinted Polyaniline Electrode Column

In order to establish an appropriate method of separation amino acidenantiomers， we chosed conductive polymer materials combined withmolecularly imprinting technique to prepare molecularly imprintedconducting polymers electrode column in this thesis. Because polyaniline(PANI) has the merits of a reversible redox properties and good conductivity,and thus from an electrochemical point of view the column packed withmolecularly imprinting PANI can be regarded as a packed-bed electrode ofthe three-electrode arrangement, which can be used to separate amino acidsopticals lsomers by controlling potential.In this thesis, conductive polyaniline was synthesized by chemicaloxidation using L-aspartate asid as template molecules. And conductivepolyaniline electrode column was fabricated by filling polyaniline intoporous ceramic tube and used as working electrode in three-electrodesystem. In this experimental study, parameters of molecularly imprintingpolyaniline electrode column such as doping time, doping potential,de-doping time, de-doping potential and so on were inestigated usingelectrochemical workstation in conjugation with fluorescence spectrometry.Eventually, the electrode column successfully separated template moleculeL-aspartate asid and its enantiomer, and the chiral selectivity coefficientcould reach4.65under the optimal situation. This column may also separatethe enantiomers of the aspartate’s analogs such as glutamic acid, and thechiral selectivity coefficient was1.84. Electrochemical quartz crystalmicrobalance (EQCM) technique was used to character the specificabsorption of the molecularly imprinting PANI to various amino acidopticals lsomers. The result revealed that this coloum can not only separatethe enantiomers of the aspartate’s analogs, it can also identify the L-asparticacid, L-glutamate and L-tryptophan, which have similar structure anddifferent molecular sizes, and the ratio of their adsorption amount was6.03:3.05:1. For broadening the scope of application of polyaniline in the aspect of pH,a copolymer (aniline-co-m-aminophenol) has been synthesized via themethod of chemical oxidation combined with molecularly imprintedtechnology. The cyclic voltammograms of the copolymer expatiated that itsdependence on pH values was decreased comparaed with PANI. Then theEQCM was used to optimize the doping/de-doping condition, andmolecularly imprinted copolymer electrode column was used to separateglutamic acid enantiomers in the optimal conditions. The chiral selectivityfactor of glutamic acid enantiomers in this electrode column can reach2.38.This kind of separation amino acid optical isomers using molecularlyimprinted conductive polymer electrode column has many anvantages, suchas simple operation, without pollution, and lower cost.