Capillary Gel Electrophoresis (CGE):

Capillary gel electrophoresis is commonly performed in a porous gel polymer matrix, the pores of that contain a buffer mixture in that the separation is carried out. In previous slab electrophoresis studies, the basic purpose of the polymeric medium was to decrease analyte dispersion through convection and diffusion and to gives a medium which could be conveniently handled for detection and scanning. It subsequently developed in which this type of medium could gives a molecular sieving action which retarded the migration of analyte species to several extents depending upon the pore size of the polymer and the size of the analyte ions. This category of sieving action is particularly helpful within separating macromolecules such as proteins, DNA fragments, and oligonucleotides which have substantially the similar charge but differ in size. Presently, most macroscale electrophoresis separations are carried on a gel slab. A few capillary electrophoretic separations of species which differ in size are also performed in gels hold in capillary tubes.

The most general type of gel used in electrophoresis is a polyacrylamide polymer formed through polymerizing acrylamide ( -CH₂ = CH - CO -NH₂) in the presence of a cross connecting agent (vide infra). The pore size of the polymer depends upon the ratio of monomer to cross linking agent. An increase in the amount of cross linking agent results in smaller pore size. Other gels which have been used for capillary gel electrophoresis involves agarose, a polysaccharide extracted from a methyl cellulose, marine alga and polyethylene glycol.