Amperometric detection of phenol with cytochrome C-modified gold electrode using dual working electrode system

The electrochemistry and amperometric sensor response for phenol of cytochrome c-modified gold electrode have been investigated. The increase in cathodic current with the concentration of H2O2 observed in cyclic voltammograms at the potential more negative than 0.0V could be considered to arise from the direct electron transfer from the Au electrode to the active site of the immobilized cyt c. The additional increase in the cathodic current with addition of phenol demonstrated the peroxidase-like activity of cyt c. The amperometric sensor response for phenol depended strongly on the applied potential. The cathodic response current, which is usually used for phenol biosensor based on horseradish peroxiclase, could not be observed due to the low peroxidatic activity of cyt c and/or the competition of the reduction of enzyme intermediates by the direct electron transfer with that by the phenol-mediated mode. This competition could be avoided by using the dual working electrode system in which the direct electron transfer was controlled by the applied potential of the first electrode, and the reaction product was detected electrochemically with the second electrode. Consequently, a cathodic response current attributable to oxidized phenol could be observed with addition of phenol at the second electrode, indicating cytochrome c to have a weak peroxidase activity.