Double potential step chronocoulometry can also be used to obtain diffusion coefficients. The model is outlined in Table 12.3, and the reversible response is shown in Figure 12.2. An advantage is that the double-step data provides a better test for reversibility than the rather featureless singlestep signal. It also provides additional information for model testing in cases where the reversible model might not apply. A disadvantage for systems with large background currents is that there is ambiguity about exactly how to account for the background.
The double potential step method works quite well on pure mercury electrodes, on which the background current is predominantly the double layer charge D values for several metal ions showed excellent precision and good agreement with values obtained from dc polarography (Table 12.2) ,
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