CHARACTERIZATION OF HUMAN SERUM-ALBUMIN HETEROGENEITY BY CAPILLARY ZONE ELECTROPHORESIS AND ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY

Human serum albumin (HSA) preparations and HSA-containing recombinant human erythropoietin (rhEPO) formulations were analyzed by capillary z one electrophoresis. HSA was separated into several components by the addition of 1,4-diaminobutane to 20 mM sodium phosphate, pH 6.0 as ele ctrophoretic buffer. Resolution was improved by increasing the buffer pH to 8.5. A comparative analysis of HSA preparations from three manuf acturers provided evidence that this method can be used to differentia te individual preparations. The analysis of rhEPO formulations, compos ed largely of HSA, showed levels of heterogeneity comparable to that o f HSA preparations. Electrospray ionisation mass spectrometry was used as an independent method to confirm the heterogeneous nature of HSA.