A family of single-isomer, sulfated gamma-cyclodextrin chiral resolving agents for capillary electrophoresis. 1. Octakis(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin.

Abstract

The first member of the single-isomer, sulfated gamma-cyclodextrin family, the sodium salt of octakis(2,3-diacetyl-6-sulfato)-gamma-cyclodextrin (ODAS-gamma CD) has been synthesized, analytically characterized, and used to separate, by capillary electrophoresis, a variety of neutral, acidic, basic, and amphoteric enantiomers in low pH background electrolytes. The anionic effective mobilities of the neutral and anionic analytes were found to increase with the concentration of ODAS-gamma CD. For weakly binding cationic analytes, the effective mobilities went from cationic high values, through zero, to increasingly larger anionic values as the concentration of ODAS-gamma CD was increased. For the strongly complexing cationic analytes, the effective mobilities became anionic even at very low ODAS-gamma CD concentrations and became smaller as the ionic strength of the background electrolyte increased with the increasing ODAS-gamma CD concentration. Separation selectivity followed the predictions of the charged resolving agent migration model: for neutral analytes it decreased as the concentration of ODAS-gamma CD was increased. For cationic analytes, selectivities were found to increase as the cationic effective mobilities approached zero, then decreased as the concentration of ODAS-gamma CD was increased further. The extent of peak resolution that could be realized with ODAS-gamma CD strongly depended on the magnitude of separation selectivity and the normalized electroosmotic flow mobility. ODAS-gamma CD proved to be a broadly applicable chiral resolving agent.