Capillary electrophoresis study of human serum albumin binding to basic drugs

The applicability of capillary electrophoresis/frontal analysis (CE/FA) for determining the binding constants of the drugs propranolol (PRO) and verap amil (VER) to human serum albumin (HSA) was investigated. After direct hydr odynamic injection of a drug-HAS mixture solution into a coated capillary ( 32 cm x 50 mu m i.d.), the basic drug was eluted as a zonal peak with a pla teau region under condition of phosphate buffer (pH 7.4; ionic strength 0.1 7) at 12 kV positive running voltage. The unbound drug concentrations measu red from the plateau peak heights had good correlation coefficients, r > 0. 999. Employing the Scatchard plot, the Klotz plot and nonlinear regression, the drug protein binding parameters, the binding constant and the number o f binding sites on one protein molecule, were obtained. The binding constan t obtained was compared to a reported equilibrium dialysis result and they are basically in good agreement.