The effect of complexation additives on analyte migration behavior in capillary electrochromatography

In capillary electrochromatography (CEC), analytes often have different mobilities in the mobile phase, and often are involved in multiple equilibria. In this paper, the migration behavior of an analyte in CEC is described by a general equation in which individual capacity factors are used to describe the tendency of the analyte to exist as the various analyte species present in a separation system, and the effects of both field and equilibrium are accounted for. The resolution of two analytes is shown to be related linearly to the ratio of their migration rates. The effect of the electroosmotic flow (EOF) in CEC is more complicated than in CE because it is experienced only by a fraction of the analyte, whereas in CE, it is experienced by all analyte species. A procedure for calculating the electrophoretic mobility of the analyte based on the fraction of the analyte in the buffer is demonstrated. The effect of the EOF on resolution is also discussed.