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Abstract. Capillary zone electrophoresis can be used to determine mobilities and diffusion coefficients for analytes. Mobilities are determined from measurements of migration times. Correction for electroosmotic flow must be made by measuring the flow magnitude using an uncharged marker substance. Diffusion coefficients can be measured from peak widths of analyte bands. Care must be taken in these measurements that the analyte concentration does not overload the system and perturb the axial homogeneity of the electric field strength. Analyte also must not adsorb to the surface of the capillary. Finally, the capillary should be operated with a power dissipation that is low enough that minimal heating of the capillary occurs. Capillary zone electrophoresis offers some advantages over other methods of determining mobilities and diffusion coefficients. These include a requirement of only small quantities of analyte at relatively low concentrations and the capability of making measurements on several substances simultaneously in mixtures.

Capillary zone electrophoresis using optically active 18-crown-6 tetracarboxylic acid (18C6H4) as chiral selector was studied for the enantiomeric separation of primary amines. From the separation of a variety of pharmaceutical drug substances, amino alcohols and amino acids, conclusions could be made concerning the influence of the chemical structure of the analytes on the separation. In addition, the effects of experimental parameters such as pH, proportion of organic modifier and buffer composition on the separation are discussed. A synergistic effect obtained by the joint application of 18C6H4 and a cyclodextrin was exploited to resolve analytes which were separated neither by the crown ether nor by the cyclodextrin.