Microcomputer-based instrumentation for multi-frequency Fourier transform alternating current (admittance and impedance) voltammetry

Abstract

Abstract Microcomputer-based instrumentation has been developed which enables high quality Fourier transform alternating current admittance and impedance voltammograms to be obtained over a wide range of frequencies and d.c. potentials. A carefully chosen phase-optimised small amplitude alternating potential waveform containing sets of frequencies which avoid harmonic or intermodular interference are periodically superimposed onto a staircase d.c. ramped voltage. Considerable versatility is available in the choise of the excitation waveform and the d.c. ramp. Frequencies in the range of about 50 to 50 000 Hz may be applied at many potentials in any given experiment. Data are reported at both macro- and microelectrodes to illustrate the excellent signal-to-noise ratios that can be obtained under conditions commonly encountered in mechanistic or analytical applications of voltammetric techniques. In the analytical context, linear plots of peak height vs. concentration were obtained when using the admittance mode for both reduction of [Fe(CN)6)]3− at a carbon fibre microelectrode and reduction of Cd2+ at a hanging mercury drop electrode. Many mechanistic and analytical applications presently associated with single frequency linear sweep and cyclic a.c. voltammetry are expected to be enhanced when the instrumentation is used in the multi-frequency mode.