Reverse Direction Anion Capillary Electrophoresis: Theory and Application

Abstract A new mode for operating capillary electrophoresis for separation of anions without using buffer modifiers has been demonstrated. Reverse direction anion capillary electrophoresis, as the new mode is designated, is performed on two anions, nitrate and nitrite, with similar electrophoretic mobilities at various buffer pH values. Since electroosmotic flow increases as buffer pH is increased, it is shown that resolution is poor at low pH and enhanced at neutral to high pH. Model equations are derived for predicting the resolution and number of theoretical plates for reverse direction anion capillary electrophoresis. From these equations, system efficiency (N) and resolution are plotted as a function of electroosmotic mobility to illustrate how performance can be improved by an increase in electroosmotic flow.