QUANTITATIVE DESCRIPTION OF ANALYTE MIGRATION BEHAVIOR-BASED ON THE DYNAMIC COMPLEXATION MODEL IN CAPILLARY ELECTROPHORESIS

A theory based on dynamic complexation is used to describe analyte mig ration behavior in capillary electrophoresis (CE). This theory is base d on a one-phase system, instead of the commonly accepted two-phase sy stem. The migration behavior of an analyte is described by three param eters (the electrophoretic mobility of the free analyte, the electroph oretic mobility of the analyte-additive complex, and the equilibrium c onstant (formation constant) that determines the fractions of the free analyte and the complex at a certain additive concentration). Varying the additive concentration shifts the equilibrium and changes the vis cosity of the background electrolyte. Viscosity correction is crucial in interpreting the observed migration behavior of analytes. While ele ctroosmotic flow in a capillary often varies from one capillary to ano ther, the viscosity of a buffer is characteristic of the buffer compos ition and is constant for each buffer. The electrophoretic mobility of a certain species and the equilibrium constant are intrinsic properti es and are less sensitive to changes in the environment. Understanding these relationships is indispensable in CE method development and met hod validation. A universal resolution equation is proposed, with a se paration factor that has taken both the electrophoretic mobilities and equilibria into consideration. This resolution equation gives clear g uidance for the optimization of CE separations. A group of nucleosides and their phosphates are used as analytes, and P-cyclodextrin is used as the additive in the model system studied in this paper. Both the o bserved analyte migration behavior and the resolution of analytes agre e well with this theory.