[Albumin-drug binding study by capillary electrophoresis. I. Quantitative applicability examination of liquid...

To measure the free concentration of verapamil (a basic drug) enantiomers in the binding system of human serum albumin(HSA), a capillary electrophoretic method, liquid precolumn(LCP), was established, and the method was examined systematically. In physiological pH condition (pH 7.4, ionic strength 0.17), HSA migrates in the opposite direction of verapamil. This electrophoretic property basically supposed the probability of preventing HSA from entering the capillary whereas a positive electric field was used. Finally, the drug enantiomers were separated by the chiral selector (45 mmol/L trimethyl-beta-cyclodextrin, pH 2.5 phosphate buffer) and the free concentration of each optical isomer in the binding system was measured. Seven samples were examined and their relative standard deviations(RSD) and the relative errors (RE) of unbound drug were 2.1%-5.02% and 1.4%-5.8%, respectively.