Ultrafast cyclic voltammetry at scan rates of up to 3 MV s−1 through a single-opamp circuit with positive feedback compensation of ohmic drop

A very simple circuit constructed by only one operational amplifier acting as a negative-impedance current-to-voltage converter is presented for ohmic drop compensation in ultrafast cyclic voltammetry, the main advantage being its simplicity and ease of reproduction. Theoretical analysis of this circuit predicts most of its characteristics, which are then confirmed experimentally on dummy cells. The reduction of anthracene in acetonitrile, a classical test example of very fast electron-transfer kinetics, is examined carefully. It is thus shown that this circuit affords excellent ohmic drop compensation to record undistorted voltammograms up to a 2.67 MV s−1 scan rate, and 3 MV s−1 can be reached if an error of 30 mV is tolerated, corresponding to an uncertainty of 20% in the determination of a standard rate constant of 5.1 cm s−1.