Over the past several years, there has been a resurgence of interest in electroanalytical chemistry, and particularly in pulse voltammetry, A great deal of the impetus for this resurgence was the work, in the 1950s, of Geoffrey Barker in England and the development, in the late 1960s in the U.S., of the first practical high-sensitivity pulse voltammetric instrument, the PARC 174 (EG&G Princeton Applied Research). Whereas conventional dc polarographic techniques had detection limits of ~10-5 M, the PARC 174, using differential pulse polarography, made it possible to attain detection limits that were easily two orders of magnitude lower. Until fairly recently, this and similar instruments, such as the IBM 225 voltammetric analyzer (IBM Instruments, Inc.), provided the best techniques in pulse voltammetry.However, more recently-again stemming from the work of Barker in the 1950s-a new technique has arisen which, in our view, surpasses and thus will soon supplant differential pulse voltammetry as the ultimate voltammetric technique. This technique, square wave voltammetry, capitalizes on the present revolution in electronics, particularly the capability of per-
SquareWave Voltammetry forming on-line computer-controlled experiments with both miniand microcomputer systems. In this article we place square wave voltammetry in the context of voltammetry in general, describe the technique and its principle attributes, and give some examples that demonstrate its power as an analytical (or mechanistic) tool.
VoltammetryVoltammetry (1-3) is concerned with the current-potential relationship in an electrochemical cell and, in particular, with the current-time response of an electrode at a controlled potential. If the potential is held-or stepped-to a value at which a faradaic process takes place involving the electrode and a solution species, then