MICROCOMPUTER-BASED INSTRUMENTATION FOR MULTIFREQUENCY FOURIER-TRANSFORM ALTERNATING-CURRENT (ADMITTANCE AND IMPEDANCE) VOLTAMMETRY

Microcomputer-based instrumentation has been developed which enables h igh quality Fourier transform alternating current admittance and imped ance voltammograms to be obtained over a wide range of frequencies and d.c. potentials. A carefully chosen phase-optimised small amplitude a lternating potential waveform containing sets of frequencies which avo id harmonic or intermodular interference are periodically superimposed onto a staircase d.c. ramped voltage. Considerable versatility is ava ilable in the choice of the excitation waveform and the d.c. ramp. Fre quencies in the range of about 50 to 50000 Hz may be applied at many p otentials in any given experiment. Data are reported at both macro-and microelectrodes to illustrate the excellent signal-to-noise ratios th at can be obtained under conditions commonly encountered in mechanisti c or analytical applications of voltammetric techniques. In the analyt ical context Linear plots of peak height vs. concentration were obtain ed 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. (C) 1997 Elsevier Science S.A.