Electrocatalysis at a Conducting Composite Electrode Doped with a Ruthenium(II) Metallodendrimer

Abstract

A pentaerythritol-based metallodendrimer with Ru^IIterpyridine units was synthesized and tested as a mediator for the electrochemical oxidation of methionine (l-Met), cystine (l-Cys), and As^III. A reversible oxidation of Ru^II was observed with the metallodendrimer as a solute in mixed acetonitrile−water solvents and as a component of carbon-based conducting composite electrodes. Mediated oxidation of the test species was observed. In aqueous solution, the composite electrode yielded a cyclic voltammetric peak current for the oxidation of l-Met in a 0.1 M phosphate buffer (pH 7.0) at 1.1 V vs Ag/AgCl. This anodic process was employed for amperometric detection in a flow system. Linear calibration curves were obtained over the range 1.0−10 μM Met and Cys. Using the criterion of the concentration yielding a signal 3 times the uncertainty of a blank, detection limits of 0.6 and 0.5 μM were calculated for Met and Cys, respectively. The slopes with three nominally identical electrodes varied by 10%.