Determination of β-blockers in pharmaceutical preparations and human urine by high-performance liquid chromatography with tris(2,2′-bipyridyl)ruthenium(II) electrogenerated chemiluminescence detection

A highly selective and sensitive detection method based on tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)₃²⁺] electrogenerated chemiluminescence (ECL) has been developed for the quantitative determination of β-blockers in both pharmaceutical preparations and human urine samples. The ECL emission is based on the reaction between electro-oxidized Ru(bpy)₃³⁺ and the secondary amino groups on the β-blockers. The ECL intensities for the β-blockers were strongly dependent on the pH at which the ECL detections were conducted, with the maximum intensities being obtained at pH 9.0. Under the optimal condition, the detection limit for atenolol and metoprolol were almost 0.5μM (50pmol) and 0.08μM (8pmol), respectively, with S/N of 3 and a linear working range that extends four orders of magnitude with relative standard deviations below 5% for 10 replicate injected samples. The concentrations of atenolol and metoprolol were determined in pharmaceutical preparations using flow injection analysis with Ru(bpy)₃²⁺ ECL detection based on standard addition method. The determined values by the present method showed acceptable agreement with the stated values by manufacturers. The determination of the five β-blockers in human urine samples was performed using HPLC-Ru(bpy)₃²⁺ ECL detection. The resulting chromatogram was much simpler than that obtained with HPLC-UV absorbance detection.