A UNIFIED APPROACH TO TRACE ANALYSIS AND EVALUATION OF ELECTRODE-KINETICS WITH FAST FOURIER-TRANSFORM ELECTROCHEMICAL INSTRUMENTATION

A microcomputer-based form of Fourier transform instrumentation, which yields potential and frequency-dependent current, admittance and impe dance data with excellent signal-to-background ratio over a wide frequ ency range, is shown to provide state-of-the-art performance in both a nalytical and kinetic applications of voltammetry. The limit of detect ion of 5 x 10(-8) to 10(-7) M found for the determination of cadmium a nd lead at a hanging mercury drop electrode, when applying a multi-fre quency excitation signal, is equivalent to that reported with single-f requency or time-domain ac, pulse and square-wave polarographs. The hi ghly effective discrimination against the charging current, which is r equired for trace analysis, can be achieved only by correction of the real part of the admittance data for the uncompensated solution resist ance (a parameter readily obtained from impedance analysis of the data ). Furthermore, excellent agreement with literature data is achieved w hen calculating the physico-chemical parameters associated with the ca dmium(II) reduction process in different media. The ability to use the same instrument to undertake analytical determinations and characteri se the electrode kinetics represents an ideal method for confirming th e fidelity of a voltammetric analysis. (C) 1998 Elsevier Science S.A. All rights reserved.