Determination of adrenaline by using inhibited Ru(bpy)32+ electrochemiluminescence

Adrenaline was found to inhibit strongly the electrochemiluminescence (ECL) from the Ru(bpy)(3)(2+)/tripropylamine system when a working Pt electrode was maintained at 1.05 V (versus Ag/AgCl) in pH 8.0 phosphate buffer. On this basis, a flow injection (FI) procedure with inhibited electrochemiluminescence detection has been developed for determination of adrenaline. The method exhibited a good reproducibility, sensitivity, and stability with a detection limit (signal-to-noise ratio = 3) of 7.0 x 10(-9) mol l(-1) and dynamic concentration range of 2 x 10(-8) to 1 x 10(-4) mol l(-1). The relative standard deviation was 2.2% for 1.0 x 10(-6) mol l(-1) adrenaline (n = 11). The method was successfully applied to the determination of adrenaline in pharmaceutical samples. Moreover, ECL emission spectra, UV-Vis absorption spectra and cyclic voltammograms of Ru(bpy)(3)(2+)/tripropylamine/adrenaline were studied. The inhibition mechanism has been proposed as the interaction of electrogenerated Ru(bpy(3))(2+)* and the o-benzoquinone derivatives, adrenochrome and adrenalinequinone, at the electrode surface. (C) 2002 Elsevier Science B.V. All rights reserved.