Sartobind® S membrane absorbent units display a macro-porous structure with a pore size> 3 μm. Sulfonic acid ligands covalently bind to the complete inner surface of the membrane, resulting in the separation of high binding capacity media in combination with extremely high flows. The Sartobind® S absorbent membrane has been used successfully in the manufacture of FDA-approved drugs to remove high-flow host cell proteins. As a cation exchanger, it shows not only the ability to remove aggregates but usually at least ten times the binding capacity for viruses and virus-like particles (VLP).