Evaluation of the stability constants of acidic and basic organic substances with 18-crown-6 and β-cyclodextrin using capillary zone electrophoresis

The possibility of evaluating stability constants in the analyte-macrocycle system by capillary zone electrophoresis was exemplified in the separation of a mixture of acids (homovanillic acid, vanilmandelic acid, 5-hydroxyindole-3-acetic acid, and 3,4-dihydroxyphenylalanine) or bases (adrenalin, noradrenalin, dopamine, serotonin, and metanephrine) with the addition of β-cyclodextrin or 18-crown-6, respectively, to the buffer electrolyte. The information content of the constants obtained in the separation of biologically important mixtures for the determination of optimum concentrations of the complex-forming agents in the running buffer is discussed.