Selective enrichment of albumin in biological samples by CE using segmental filling with sodium octyl sulfate in the background electrolyte.

This paper shows that in CE, the peak efficiency and effective electrophoretic mobility of HSA and BSA were significantly enhanced by using a short plug (8 nL) of 1% w/w sodium octyl sulfate (SOS) and 1% w/v dextran sulfate as the additive. However, under identical conditions, other proteins did not exhibit the same phenomena. When the concentration of SOS was increased to 1.0% w/w SOS, a broad peak that corresponded to HSA transformed to a sharp peak. When the SOS concentration was more than 3.0% w/w, there was no shift in the effective electrophoretic mobility of HSA (10 microM), indicating that the binding of SOS to HSA is saturated. Through the specific interaction between SOS and HSA, the selective sweeping of HSA was accomplished using a short plug (24 nL) of 1% w/w SOS, followed by the injection of 190 nL of the sample. The excellent peak efficiency was still obtained for HSA and BSA upon the injection of a large-volume sample. As a result, the LOD for HSA (S/N=3) was 0.1 nM. In contrast to the normal injection without the SOS plug, approximately, a 4000-fold increase in the sensitivity of HSA was obtained by using the sweeping method. The proposed method has been successfully applied for the quantification of HSA in urine and erythrocytes as well as the quantification of BSA in milk.