Anodic Stripping Voltammetry

As illustrated here, anodic stripping voltammetry (ASV) consists of two steps. The first step is a controlled potential electrolysis in which we hold the working electrode—usually a hanging mercury drop or a mercury film electrode—at a cathodic potential sufficient to deposit the metal ion on the electrode (in this case the reduction of Cu2+ to Cu, which forms an amalgam with Hg).

Figure11.46

This step essentially serves as a means of concentrating the analyte by transferring it from the larger volume of the solution to the smaller volume of the electrode. During most of the electrolysis we stir the solution to increase the rate of deposition. Near the end of the deposition time we stop the stirring—eliminating convection as a mode of mass transport—and allow the solution to become quiescent. Typical deposition times are 1–30 min are common, with analytes at lower concentrations requiring longer times.

In the second step, we scan the potential anodically—that is, toward a more positive potential. When the working electrode’s potential is sufficiently positive, the analyte is stripped from the electrode, returning to solution in its oxidized form. Monitoring the current during the stripping step gives the peak-shaped voltammogram shown above.

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