4.4.4 Capillary Gel Electrophoresis (CGE)

Capillary gel electrophoresis is essentially gel electrophoresis conducted in a capillary tube. The “gel” is not necessarily stiff and solid as it is in slab gel electrophoresis. To avoid confusion, it is usually referred to as a polymer matrix. Many polymer matrices are available and offer different separating properties.

The polymer is dissolved in buffer and loaded into the capillary tube. Generally, the polymer concentration necessary for adequate separation is inversely proportional to the size of the analyte. As low viscosity polymer solutions do not experience the same capillary action as most regular buffer solutions, the capillary gel is often pumped with pressure and the capillary wall is coated to eliminate EOF.

There are generally 10 million theoretical plates per meter of capillary tubing.  CGE is most commonly used to separate single-stranded oligonucleotides, proteins, and DNA fragments.

As in CZE, it is possible to add agents such as chiral selectors and ion-pairing agents by covalently bonding them to the gel or the running buffer. This can greatly increase the separation possibilities of a single system.