Electrochemiluminescence quenching as an indirect method for detection of dopamine and epinephrine with capillary electrophoresis

An electrochemiluminescence (ECL) inhibition method was developed as an indirect detection method for the determination of dopamine and epinephrine separated by capillary electrophoresis (CE). When the concentration of Ru(bpy)(3)(2+) was 50 mu m diluted by 50 mm phosphate (pH 8.5) in the cell and 0.5 m tripropylamine (TPA) was added to the running buffer (10 mm phosphate, pH 9.0), an inhibition of ECL of the Ru(bpy)(3)(2+)/ TPA system by the analytes was observed. Under the optimized conditions, the relative standard deviations of migration time and negative peak area were less than 1% and 3%, respectively, for 1 mu m dopamine or 1 mu m epinephrine (n = 10). Linear ranges of 0.1-10 mu m for both analytes and the detection limits (signal-to-noise ratio S/N = 3) of 10 nm for dopamine and 30 nm for epinephrine were obtained.