A unified approach to trace analysis and evaluation of electrode kinetics with fast Fourier transform electrochemical instrumentation

摘要

A microcomputer-based form of Fourier transform instrumentation, which yields potential and frequency-dependent current, admittance and impedance data with excellent signal-to-background ratio over a wide frequency range, is shown to provide state-of-the-art performance in both analytical and kinetic applications of voltammetry. The limit of detection of 5 * 10~(-8) to 10~(-7) M found for the determination of cadmium and lead at a hanging mercury drop electrode, when applying a multi-frequency excitation signal, is equivalent to that reported with single-frequency or time-domain ac, pulse and square-wave polarographs. The highly effective discrimination against the charging current, which is required for trace analysis, can be achieved only by correction of the real part of the admittance data for the uncompensated solution resistance (a parameter readily obtained from impedance analysis of the data). Furthermore, excellent agreement with literature data is achieved when calculating the physico-chemical parameters associated with the cadmium(II) reduction process in different media. The ability to use the same instrument to undertake analytical determinations and characterise the electrode kinetics represents an ideal method for confirming the fidelity of a voltammetric analysis.