DISPERSION IN CAPILLARY ELECTROPHORESIS WITH EXTERNAL FLOW-CONTROL METHODS

Recently, methods for controlling the bulk how of the buffer which are independent of the electrophoretic migration have been demonstrated in capillary electrophoresis (CE) systems. These methods include controlling the electroosmosis by radially directed electric fields, and controlling the bulk flow by siphoning. This paper investigates basic dispersion mechanisms at work by examining the dispersion of dimethyl sulfoxide under various external control methods. It is found that the electroosmotic how control methods exhibit the same dispersive behavior as the conventional CE system. In particular, the results for pH 7 buffers obey the theoretical expression for the plate height in all configurations. However, in all configurations, pH 2.7 buffers do not follow the theory, and counter to intuition, additional pressure can improve the plate height at pH 2.7. Taking all these methods together, one can develop a technique to appropriately adjust the electrophoretic and bulk how to optimize resolution.