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.