Media and devices, such as anion exchangers including such media, wherein the media is a membrane having a surface coated with a
polymer such as a polyallylamine. The resulting membrane offers stronger binding of
protein impurities and superior removal of host
cell proteins from biological samples than conventional ligands based on
quaternary ammonium salts, including trimethylammonium ligands. Also described is a
chromatography scheme and method for purifying
monoclonal antibodies, wherein the anion exchange sorber is placed downstream of an affinity column (such as
Protein A or
Protein G affinity column) and optionally one or more
polishing devices such as
cationic exchange columns. Little or no
dilution of the cation exchanger
pool (or affinity column exchange
pool where no cation exchanger is used) is necessary to lower the
conductivity of the sample. The sorber functions well to strongly bind host
cell proteins and other impurities in biological samples even at high conductivities and pH.