Abstract
An internal-surface reversed-phase silica column was employed in the frontal analysis method to determine free drug concentration in warfarin (Wf)-bovine serum albumin (BSA) mixed solution and in indometacin(Im)-BSA mixed solution.When a 4-ml portion of aqueous solution containing 2-30 μM Im and 28 μM BSA and a 10-ml portion of aqueous solution containing 0.5-175 μM Wf and 28 μM BSA were applied, the elution curves reached a plateau level corresponding to both free drug and drug-BSA complex (β-plateau), followed by another plateau due to free drug alone (γ-plateau). The drug concentration at the γ-plateau agreed well with the free drug concentraion determined after ultrafiltration of the same solution.The γ-plateau was observed even when the applied volume was reduced to a level which was insufficient to produce the β-plateau. The infection of a 400-μl portion of the 0.5-100 μM Im and 28 μM BSA mixed solution and a 90-μl portion of 50 μM Im and 550 μM BSA mixed solution onto the ISRP silica column gave a clear γ-plateau. Compared to the conventional frontal analysis, the present method can determine a wide range of drug levels with much smaller injection volume. This method is applicable to plasma. By a single frontal analysis, both free and total concentrations of carbamazepine in plasma were determined simultaneously.
