Migration behavior of dichlorophenols for replicate separations without replenishment of buffer electrolyte in micellar electrokinetic capillary chromatography

The migration behavior of dichlorophenols in replicate separations, without replenishment of buffer electrolyte between runs, in micellar electrokinetic capillary chromatography (MECC) was investigated. The results indicated that the pH of the buffer electrolyte drifts as a result of electrolysis of the buffer solution during electrophoresis and that the pH drift, being independent of the micelle concentration, is responsible for the variation in electrophoretic mobilities of analytes in MECC when the buffer is not replenished. The influences of the buffer pH and micelle concentration on the migration behavior of analytes were demonstrated to be correlated at small micelle concentrations. The variation of electrophoretic mobility of an analyte as a function of buffer pH at a given micelle concentration is quantitatively described. 2,6-Dichlorophenol is selected for illustration. The variation of electrophoretic mobility agrees satisfactorily between predicted and observed data.