Characterisation 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 zone electrophoresis. HSA was separated into several components by the addition of 1,4-diaminobutane to 20 mM sodium phosphate, pH 6.0 as electrophoretic buffer. Resolution was improved by increasing the buffer pH to 8.5. A comparative analysis of HSA preparations from three manufacturers provided evidence that this method can be used to differentiate individual preparations. The analysis of rhEPO formulations, composed largely of HSA, showed levels of heterogeneity comparable to that of HSA preparations. Electrospray ionisation mass spectrometry was used as an independent method to confirm the heterogeneous nature of HSA.