Capillary Isoelectric Focusing (CIEF):

This technique permit amphoteric molecules, such as proteins, to be separated through electrophoresis in a pH gradient generated among the cathode and anode. A solute will migrate to a point whereas its net charge is zero. At the solutes isoelectric point (pI), migration stops and the sample is focused within a tight zone. In CIEF, once a solute has focused at its pI, the zone is mobilized past the detector through either pressure or chemical means. This method is generally employed in protein features as a mechanism to determine a protein's isoelectric point.