What is electrophoresis? Definition Capillary electrophoresis is an analytical technique that separate ions based on their electrophoretic mobility with the use of an applied voltage.  Basics The electrophoretic mobility is dependent upon the charge of the molecule, the viscosity and the atom's radius. The rate at which particle moves is directly proportional to the applied electric field, the greater the strength the faster the mobility. Neutral species are not affected, only ions move with the electric field. If two ions are the same size, the one with greater charge will move faster. For ions of the same charge, the smaller particle has less friction and overall faster migration rate. Capillary electrophoresis is used most predominately because it gives faster results and provides high resolution separation. It is useful technique because there is a large range of detection methods available.