The Preparation And Application Of Adsorbents For Aromatic Amino Acids And Endotoxin

The objective for this thesis is to develop sorbents for adsorption of aromatic amino acids (AAA) based onβ-cyclodextrin (β-CD) and endotoxin based on polymyxin B immobilized sorbents.A cross-linkedβ-CD polymer was prepared and investigated systematically for adsorption of AAA from aqueous solutions based on cavity inclusion effect. It was observed that the equilibrium was gradually achieved in about 45 min and the adsorption ratio was relatively high at the beginning. Decreased temperature, increased NaCl concentration, an intermediate pH and the polymer prepared at a higher temperature favored the adsorption. The adsorption generally approached the Freundlich isotherm equation. Under the same conditions, the adsorption ratio of AAA on the polymer was as follows, L-tryptophan > L-phenylalanine > L-tyrosine. Compared with the adsorption of branched-chain amino acids, the polymer showed higher selectivity for AAA. The molecular structure, hydrophobicity and charged states of amino acids were responsible for the difference in adsorption.An ethylatedβ-CD polymer was prepared and investigated for adsorption of AAA from aqueous solutions. The features of AAA adsorbed on the ethylatedβ-CD polymer were similar with those of the parentalβ-CD polymer, but theadsorption ratios of AAA on the ethylatedβ-CD polymer were higher than those of the parentalβ-CD polymer. It may be due to the strengthened hydrophobic interactions between AAA and the ethylatedβ-CD polymer, which was caused by the ethylation of the parentalβ-CD polymer.A positively chargedβ-CD polymer was prepared. This polymer bears two kinds of binding sites, one being the hydrophobic cavity and the other, the cationic part of ammonium ion. The adsorption behaviors of AAA on the polymer were investigated based on the cooperation of the electrostatic and hydrophobic interactions between AAA and the polymer.Three affinity matrices for adsorption of endotoxin from aqueous solutions were prepared by covalently bonding polymyxin B varying the length of spacer arm to Sepharose CL-4B. The effect of the length of spacer arm on ligand densities and endotoxin adsorption was studied. Also the optimum conditions for adsorption of endotoxin from aqueous solutions were investigated.