Simultaneous Scanning Electrochemical Microscopy and UV-Vis Absorption Spectroelectrochemistry

The combination ofinstrumental techniques allows obtainingpreciseand reliable information about the reactions taking place at the electrode/solutioninterface. Although UV-Vis absorption spectroelectrochemistry (UV-Vis SEC) providesa molecular insight about the species involved in the electrode process,obtaining information about the redox state of the products generatedin this process is not always accessible by this technique. In thissense, scanning electrochemical microscopy (SECM) has a clear advantage,since it provides additional information on the oxidation state ofthe intermediates/products. Therefore, the combination of these twotechniques facilitates obtaining a more complete picture of the electrochemicalreaction studied from two different points of view, but under exactlythe same experimental conditions. In this work, the combination ofUV-Vis SEC in parallel configuration and SECM is carried outfor the first time. This new technique allows distinguishing betweenthose species that are electrochemically active and, at the same time,exhibit changes in the UV-Vis absorption spectra during theelectrochemical reaction. The new experimental setup is first validatedusing ferrocenemethanol as a standard probe, concomitantly obtainingspectroscopic and electrochemical information that accurately describesthe oxidation process. Finally, the strength of this combined techniqueis demonstrated by studying the antioxidant activity of o-vanillin (o-HVa) in the presence of electrogeneratedsuperoxide. The information extracted from the new UV-Vis SEC/SECMtechnique makes it possible to identify, beyond any doubt, not onlythe origin of the electrochemical signals recorded in the SECM tipbut also to evaluate the antioxidant effect of o-HVaat different concentrations.