Quarter-peak potential

Alternatively, the determination of k may be based on measurements of Ep/4 — Ep mam where the quarter-peak potential Ep/4 is the value of E at i = ip,mam/4 [123] [see Fig. 17(a)]. The advantage of this approach is that measurements can be made even in cases where the prepeak appears only as a shoulder on the main peak, and where Ep.pre therefore cannot be determined. The working curve for the eCen mechanism is shown in Fig. 17(b) together with experimental data obtained for the protonation of the anthracene radical anion by benzoic acid. The rate constant resulting from these data is 2.7 X 10 M s [123]. 

This term denotes a potential whose nature depends on the technique used. Typical characteristic potentials are the half-wave potential in polarography, the quarter-transition-time potential in chronopotentiometry, and the peak or half-peak potential in stationary-electrode voltammetry. Regardless of its nature, the characteristic potential always depends on the identity of the electroactive substance, on the kinetics or thermodynamics of the electron-transfer process, and of course on the experimental conditions for any particular technique and under any completely defined set of experimental conditions the value of any characteristic potential is a reproducible property of the electroactive substance. 

Figure 9A A spline function consisting of two quarter-sine waves connected by a straight line is used to smooth the transition between high and low potentials during simulated square-wave voltammetry (black line). The open circle shows the time when current is measured for the end of peak potential. The gray line shows the ideal unsmoothed transition.

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