Though it is a variation of electrophoresis it has become a most powerful tool for separating mixtures of proteins . In this method the column is filled with a gel having varying ratios of positive and negative charges. The protein mixture is placed inside the column and the molecules migrate in the electric field in such a way that the negatively charged ones move to the anode and those with positive charges move towards the cathode. As the proteins migrate in electric field, they are exposed to varying pH and at some point in the tube each protein encounters a pH at which it becomes neutral and stops migrating . This pH is the isoelectric point at which the protein forms a very sharp band.

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