Improved separation of diastereomeric derivatives of enantiomers by a physical network of linear polyvinylpyrrolidone applied as pseudophase in capillary zone electrophoresis.

Diastereomeric analytes were separated using capillary zone electrophoresis with polyvinylpyrrolidone as polymeric additive to the buffer solution. As test substances derivatives of D- and L- alpha-amino and alpha-hydroxy acids formed by reaction with (+)-O,O'-diacetyl- and (+)-O,O'-dibenzoyl-L-tartaric anhydride, respectively, were used. The physical network formed by the linear polymer is supposed to act as a kind of pseudophase. It was found that the network affects the mobility of diastereomeric compounds to a different extent, enhancing the selectivity of the system. In nearly all cases of aromatic acids the diastereomer carrying the D-amino acid was more strongly retained than the L-isomer, as opposed to the situation with aliphatic acids.

Enantiomers resolution in capillary zone electrophoresis by using cyclodextrins.

Cyclodextrins added to the background electrolyte are shown to be useful for the resolution of racemic compounds in their enantiomers. Several parameters have to be controlled in order to achieve resolution, e.g., cyclodextrin type, concentration, analyte shape, as well as column temperature. The resolution of nor-epinephrine, epinephrine and isoproterenol in their enantiomers decreased by increasing the column temperature. Octopamine and ketamine have been resolved by supporting the background electrolyte with 2, 6-di-O-methyl-beta-cyclodextrin. In spite of the stronger inclusion-complex of ketamine than octopamine with the modified cyclodextrin its resolution was not satisfactory.