ABSTRACT
Transferrin and albumin are often present in immunoglobulin G (IgG) concentrates and are considered as impurities. Therefore, it is important to determine their concentration in order to obtain a well-characterized biological product. Here, we describe their determination based on conjoint liquid chromatography (CLC). The established method combines two different chromatographic modes in one step: affinity and ion-exchange chromatography (IEC) combined in one column. Therefore, two CIM Protein G and one CIM quaternary amine (QA) monolithic disks were placed in series in one housing forming a CLC monolithic column. Binding conditions were optimized in a way that immunoglobulins were captured on the CIM Protein G disks, while transferrin and albumin were bound on the CIM QA disks. Subsequently, transferrin and albumin were eluted separately by a stepwise gradient with sodium chloride, whereas immunoglobulins were released from the Protein G ligands by applying low pH. A complete separation of all three proteins was achieved in less than 5 min. The method permits the quantification of albumin and transferrin in IgG concentrates and has been successfully validated.