Ion chromatography using anion-exchangers modified with dextran sulfate

Summary Retention behavior of anions and cations on anion-exchangers modified with dextran sulfate has been investigated. Retention of anions was remarkably reduced by the modification, and the retention factor decreased with decreasing eluent concentration when sodium sulfate was used as the eluent. Cations were also retained on the modified stationary phase, and alkali and alkaline-earth metal ions were separated using copper sulfate or tris(2,2′-bipyridyl)ruthenium chloride as eluent. The size of the dextran sulfate strongly affected the retention behavior of analyte ions.     

Separation of enantiomers on anion exchangers modified with heparin in liquid chromatography

Hepatitis B virus surface antigen (HBsAg) particles were efficiently adsorbed (retained) on a Sulfate-cellulose (S-C) bead column, and then desorbed with sodium chloride solutions (0.5-3.0 M). The HBsAg particles were not efficiently retained onto either sulfopropyl-agarose (SP-A) or quaternary amine-agarose (Q-A) at pH 4.5, 6 and 8. The size-exclusion curve showed that proteins of molecular mass higher than ca. 20,000 cannot penetrate into the pores of S-C beads. The dynamic binding capacity (DBC) values of lysozyme (ca. 7 mg/ml-gel) and of gamma-globulin (ca. 3 mg/ml gel) for S-C did not depend on the flow velocity while the DBC of gamma-globulin for SP-A decreased sharply with an increase in flow velocity. These results indicated that very large molecules are adsorbed only onto the surface of S-C, which resulted in fast adsorption-desorption rates although the equilibrium adsorption capacity is lower than conventional porous gel beads. Because of the rapid adsorption rate, the DBC values of gamma-globulin for S-C at high flow-rate regions are similar to those for SP-A. Bovine serum albumin was not adsorbed onto S-C. As this can not be explained by a simple electrostatic interaction mechanism, molecular recognition of S-C might be different from the agarose-based ion-exchange beads.     

Effect of eluent composition on retention behavior of anions in ion chromatography on anion-exchangers modified with heparin

Effects of eluent composition on retention behavior of inorganic anions have been investigated in ion chromatography using anion-exchangers modified with heparin. Both cation and anion of the eluent affected the retention of analyte anions and unusual retention behavior was observed on the modified stationary phase. The retention time of anions decreased with decreasing eluent concentration when sodium sulfate, magnesium sulfate and chlorides of alkali metals were used as the eluent, whereas it increased with decreasing eluent concentration when aluminum sulfate, copper sulfate and sulfuric acid were used as the eluent. The retention of nitrate increased in the order of Li⁺, Na⁺, K⁺, Rb⁺ and Cs⁺ when their chlorides were used as the eluent. When sodium perchlorate and chlorides of alkaline-earth metals were used as the eluent, the eluent should include heparin. Otherwise, the modifier was partially bled from the column.