Determination of the number of binding sites and binding constant between diltiazem hydrochloride and human serum albumin by ultrasonic microdialysis coupled with online capillary electrophoresis electrochemiluminescence

A simple, sensitive and selective determination of diltiazem hydrochloride (DLT) is described using capillary electrophoresis electrochemiluminescence (CE-ECL). The CE-ECL parameters that affect separation and detection were optimized. Under the optimized conditions, the linear range of DLT was from 0.02 to 100 μmol/L (r2 = 0.9983), with the detection limit of 5.1 nmol/L (3σ). The relative standard deviations of ECL intensity and the migration time were <2% for 0.1 μmol/L and 22 μmol/L DLT (n = 11). A new technique for determining of the number of binding sites and binding constant between DLT and HSA was developed using ultrasonic microdialysis coupled with CE-ECL. The number of binding sites and binding constant were 5.9 and 6.3 × 104 L/mol, respectively. The time required for ultrasonic microdialysis was 10 times less than that for traditional dialysis. Compared with traditional dialysis, ultrasonic microdialysis is simple, rapid, and should be applicable to a wide range of interactions of drugs and biomacromolecules.