Capillary isoelectric focusing

Capillary isoelectric focusing (CIEF) provides excellent resolution of proteins with the advantage that separations are carried out in a capillary format with on‐tube detection and automated analysis. Recent advances in the technique provide improved resolution, reproducibility and reliability. This review summarizes improvements in sample preparation, capillary selection, and focusing and zone mobilization procedures which have helped CIEF become a more robust analytical method. New applications are reviewed, in particular the use of CIEF in analysis of biopharmaceutical products.