Electrochemical behavior of FAD at a gold electrode studied by electrochemical quartz crystal microbalance

The electrochemical behavior of flavine adenine dinucleotide (FAD) at a gold electrode involving adsorption of the reduced form FADH2 and desorption of the oxidized form FAD has been studied by using electrochemical quartz crystal microbalance (EQCM). EQCM can present information not only about the electrochemical behavior but also about the mass changes on the electrode surface. The electrochemical properties and frequency shifts were investigated in FAD solutions at different pH values, concentrations and scan rates. Reversible voltammograms were observed when pH<4.5 and irreversible voltammograms were found when pH≥4.5. It is found to be a diffusion controlled process when the concentration of FAD is lower than 2 × 10−4 mol l−1 (pH 1.5). On the contrary, at concentrations higher than 2 × 10−4 mol l−1 (pH 1.5), it is found to be an adsorption controlled process.