ISOPROTEIN ANALYSIS BY ION-EXCHANGE CHROMATOGRAPHY USING A LINEAR PH GRADIENT COMBINED WITH A SALT GRADIENT

Isoproteins of human monoclonal antibodies with a pI range between 8.4 5 and 8.70 or 8.15 and 8.65 were separated by ion-exchange chromatogra phy with a linear ascending pH gradient combined with a linear descend ing salt gradient using borax, mannitol and salt. The isoproteins were eluted according to their isoelectric points as demonstrated by conve ntional isoelectric focusing. Preparative purification and monitoring of the isoprotein composition of human monoclonal antibodies during a purification process is also presented to demonstrate the applicabilit y of the method.