Throughout the purification process the purity of the pooled target protein fraction should be monitored regularly. Denaturing polyacrylamide gel electrophoresis (PAGE) is the most popular visually accessible technique used to monitor the purity of the pooled protein fractions. A homogeneous band on both denaturing and non-denaturing PAGE is a better indication of the purity of the protein fraction. Electrophoresis is a highly resolving technique, routinely used to monitor the purity of pooled protein fractions produced by chromatographic separations. A protein purification balance sheet provides the data necessary to measure both the value of the chromatography run that has been performed and the overall effectiveness of the purification schedule. The electrophoresis of proteins in the absence of a detergent is described as non-denaturing PAGE or native PAGE. The proteins are applied to the gel and subjected to electrophoresis in their native conformations.