Enantiomer separation of basic drugs by capillary electrophoresis using ionic and neutral polysaccharides as chiral selectors.

The enantiomer separation of basic drugs by capillary electrophoresis was investigated employing two types of polysaccharides as chiral selectors. One type consists of electrically neutral polysaccharides such as dextran and dextrin, in which the separation mode is capillary zone electrophoresis (CZE), and ionic drugs are suitable for this mode. The other consists of ionic polysaccharides such as chondroitin sulfate C. Chondroitin sulfates are known as mucopolysaccharides and natural components, being charged, linear, sulfated polysaccharides of high mass. Therefore, the latter approach can be classified as affinity electrokinetic chromatography (AEKC). Both ionic and neutral drugs can be separated by AEKC owing to its separation principle. The separation of enantiomers of some basic drugs such as diltiazem and trimetoquinol was investigated with both CZE and AEKC employing polysaccharides as mentioned above and the enantioselectivity was compared. A brief mechanism of enantiorecognition by polysaccharides is also described.

Enantiomeric separation of drugs by affinity electrokinetic chromatography using dextran sulfate.

Dextran sulfate (sodium salt), which is a mixture of a linear alpha-(1,6)-linked D-glucose polymer having a sulfate group in the molecule, has been employed as a chiral selector in affinity electrokinetic chromatography (EKC) for the separation of enantiomers of drugs. Enantiomers of trimetoquinol hydrochloride and its positional isomer have been successfully separated by the method using a 3-5% dextran sulfate buffer solution of pH 5.5 within 20 min. The effects of buffer pH, concentration of dextran sulfate, and additives (such as an organic solvent, urea and a surfactant) on the enantioselectivity were investigated. The choice of pH and the concentration of dextran sulfate has been important for the improvement in selectivity.