Voltammetric Determination of Both Concentration and Diffusion Coefficient by Combinational Use of Regular and Microelectrodes

Two Pt disks with 1.6 and 0.1 mm diameter, whose sizes were accurately evaluated, were applied to voltammetric diffusion-controlled currents to determine the concentrations of redox species. Since voltammetric peak currents at a regular electrode, Ip, and limiting currents at a microelectrode, IL, are proportional to D 1/2 and D, respectively, the ratio Ip 2 /IL is independent of the diffusion coefficient but dependents on the concentration. We used this fact to determine the concentrations of ferrocenyl derivatives, hemin, hexacyanoferrate(II), dioxygen gas and hydrogen gas. New insights are not only the absolute determination of concentrations but also the sensitive detection of adsorption of electrochemical products which blocked the voltammetric currents.