Electrochemical Impedance Spectroscopy Study of Concanavalin A Adsorption on Glassy Carbon Electrode: An Analysis of Capacitance Dispersion

• Concanavalin A adsorbs at a maximum coverage of 0.23 on glassy carbon electrode.
• The adsorption of Concanavalin A on glassy carbon is irreversible.
• A graphical methodology to extract capacitance dispersion information is described.
• Capacitance dispersion is higher at more cathodic potentials.
• Adsorption is oriented side on with electrical dipole parallel to the surface.

Electrochemical impedance spectroscopy has been used to investigate the adsorption of concanavalin A lectin on glassy carbon electrode in 0.15 M NaCl solution as a function of electrode potential in the range of 0.2 to 0.8 V vs. Ag/AgCl. Under such conditions a maximum coverage of 0.23 is obtained. A graphical procedure is described to extract relevant information on the electrical behavior in terms of capacitance dispersion (Constant Phase Element, CPE). It is found that the protein does not desorb in the potential range investigated. Potential dependent capacitance dispersion is observed, being highest at more cathodic potentials. With additional information from electrostatic potential calculations the results indicate that the protein is adsorbed with a side-on orientation having its dipole moment oriented parallel to the surface.

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