Comparison of three different configurations of dual ultramicroelectrodes for the decomposition of S-Nitroso-L-glutathione and the direct detection of nitric oxide

Abstract

We report on the characterization and use of three configurations of dual gold ultramicroelectrodes (UMEs), namely a ring-disc electrode, a disc-disc electrode, and band-band electrode. These can be used for the direct determination of nitric oxide that is released during the copper-catalyzed decomposition of S-nitroso-L-glutathione (GSNO). The dual UMEs were electrochemically characterized by using ferrocenemethanol as a soluble redox mediator during chronoamperometric measurements. The data are similar to those reported in the literature for various configurations and can be used to characterize the ability of copper ions to reach the vicinity of the NO sensor. One UME was electrochemically modified with layers of a poly(eugenol)/poly(phenol) composite to act as an NO sensor. The second UME was electrochemically coated with a copper layer that serves as a source for Cu(II) that is needed for the in-situ decomposition of GSNO. The mediated decomposition of GSNO is accomplished in presence of ascorbate that acts as reducing agent for Cu(II). The NO released from GSNO is detected at the same potential as applied to form the Cu(II)-based catalyst (+0.8 V vs Ag/AgCl).