Page 154 - Analytical Electrochemistry 2d Ed - Jospeh Wang

QUESTIONS 139

3. Explain clearly why a carbon composite disk electrode offers improved signal-
to-background characteristics compared to a carbon disk electrode of the same
geometric area.
4. Describe clearly why the oxidation of polypyrrole ®lm results in the uptake of
an anion from the surrounding solution.

5. Derive the Levich equation for the limiting current at the rotating disk electrode
[based on combining equations (4-4) and (1-12)].
6. How can you use the rotating ring disk electrode for detecting short-lived
intermediate species?
7. Explain clearly why effective compensation of the ohmic drop is essential for
diagnostic applications of cyclic voltammetry (e.g., estimating n from DE ).
p
8. Describe the rationale of using electrodes coated with Na®on ®lms for selective
detection of the cationic neurotransmitter dopamine in the presence of the
common interference from anionic ascorbic acid.
9. Explain the reason for including the time-consuming oxygen removal step in
pulse-polarographic measurements of tin ion in juice samples.
10. Explain clearly why and how a change of the scan rate affects the shape of the
cyclic voltammetric response of an ultramicroelectrode.

11. Propose a modi®ed electrode surface suitable for detecting in-situ micromolar
concentrations of ferric ion in an industrial stream. What are the challenges of
such in-situ monitoring?