Polishing with membrane chromatography (MC) has achieved acceptance as state-of- the-art technology for charged impurities. Traditionally, anion-exchange (AEX) and cation-exchange (CEX) membrane chromatography have been used to remove charged contaminants such as host-cell proteins (HCPs), recombinant DNA, protein A, endotoxins, and viruses. In monoclonal antibody (MAb) processes, polishing steps usually follow a protein A affinity column step. In some cases, CEX capture is applied, either with at least one AEX or a combined AEX and CEX step. The latter may…