Question

Explain why capillary electrophoresis can offer higher separation efficiency, i.e. higher N per unit length of the column, than liquid chromatography

Answer 1

Electrophoresis is a separation technique based on the differential transportation velocities of charged species in an electric field through a conductive medium. The narrow tubes used in capillary electrophoresis help to give the technique good resolution. When a sample is introduced in a tube and an electric field applied — the components move at different rates leading to separation. The advantages of using capillary tubes are that lateral diffusion effects are reduced and temperature differences across the tube are reduced.

The properties of the tube, lead to what is known as plug flow where the velocity of the fluid is considered constant across the tube’s cross-section, perpendicular to the flow. Under plug flow, axial diffusion is the only factor leading to dispersion, so the separation efficiency using CE is very high.