Introduction to Capillary Electrophoresis of DNA: Biomedical Applications

Capillary electrophoresis (CE) separations are carried out inside a capillary tube, which usually has a diameter of 50 μm to facilitate temperature control. The length of the capillary differs in different applications, but it is typically in the region of 20–50 cm. The capillaries most widely used are fused silica covered with an external protective coating. A small portion of this coating is removed to form a window for detection purposes. The ends of the capillary are dipped into reservoirs filled with the electrolyte. Electrodes made of an inert material such as platinum are also inserted into the electrolyte reservoirs to complete the electrical circuit. The capillary is filled with running buffer, one end is dipped into the sample, and an electric field (electrokinetic injection) or pressure is applied to introduce the sample inside the capillary. Migration through the capillary is driven by application of a high-voltage current (10–30 kV).