Analysis of glycated hemoglobin A1c by capillary electrophoresis and capillary isoelectric focusing.

Two capillary electrophoretic methods were developed and evaluated for measurement of glycated hemoglobin A1c (HbA1c). First, a capillary electrophoresis analysis is performed with a sodium tetraborate buffer (pH 9.3) as background electrolyte in a neutrally coated capillary. HbA1c is separated from HbA0 due to specific interactions of borate anions with the cis-diol pattern in the saccharide moiety of glycohemoglobin. Second, a capillary isoelectric focusing method, which exploits a difference in pI values of HbA0 and HbA1c, is performed with Servalyt pH 6-8 or alternatively with Biolyte pH 6-8 carrier ampholytes spiked with a narrow pH cut of pH 7.2 prepared by preparative fractionation of Servalyt pH 4-9 carrier ampholytes. Both methods reflect recent developments in the methodology of capillary electrophoresis. They allow quantifying HbA1c in generic capillary electrophoresis analyzer with specificity that is consistent with previously reported electrophoretic assays in slab gels and capillaries.