PROPERTIES OF MULTIVARIATE BINDING ISOTHERMS IN CAPILLARY ELECTROPHORESIS

When more than one complexation additive is used in capillary electrop horesis (CE), the migration behavior of an analyte can be described us ing contour plots and profile plots of the multivariate binding isothe rms, At a certain concentration of one additive, the net electrophoret ic mobility of the analyte is not affected by the concentration of the second additive, even though the second additive does alter the mobil ity of the analyte when used alone. The concentration of the first add itive, in this situation, is defined as the dengsu concentration (deng su means ''same speed'' in Chinese), The presence of a dengsu concentr ation for one additive is a strong indication that the second additive interacts with the analyte in a 1:1 (analyte-additive) stoichiometry, The binding isotherms in a profile plot can be used to unambiguously determine the binding stoichiometry of the analytes, as well as to det ermine the effect of interactions between the additives. The apparent complex mobilities obtained from the profile plots can also be used to determine whether there are interactions between the additives or whe ther the analyte can bind both additives at the same time.