Page 114 - Analytical Electrochemistry 2d Ed - Jospeh Wang

QUESTIONS 99

Solution From Table 3-4:
i ˆ KCU 1=3
l
4
2:4: ˆ K 1 10 †0:9 1=3 K ˆ 2:49 10 4
4
1:6 ˆ 2:49 10 C†1:25 1=3
C ˆ 6 10 5 M

QUESTIONS

1. Describe clearly the principle and operation of potentiometric stripping analysis
(PSA). How it is differed from anodic stripping voltammetry (ASV)? What is
the quantitative signal? What is its advantage over ASV?

2. Draw clearly schematic diagrams of a thin-layer ¯ow detector utilizing (1) single
working electrode, and (2) dual electrode. Explain how the latter improves the
power and information content.

3. Describe and draw clearly the waveform employed in square-wave voltammetry.
Explain how the current is measured.
4. Describe clearly the use of polarographic analysis for obtaining the values of the
formation constant and stoichiometric number of metal complexes.
5. Describe clearly the challenges of interfacing electrochemical detectors to
capillary electrophoresis separation systems. How can these challenges be
overcome?
6. Explain clearly how and why the coupling of stripping voltammetry to a
differential pulse waveform can enhance the power of stripping measurements
of trace metals.

7. Select an electroanalytical technique most suitable for detecting trace levels of
nickel in ground water. Justify this choice.
8. A liquid chromatographic experiment resulted in the same retention time for the
electroactive compounds A and B. Which electrochemical detection scheme
would offer a selective detection of the two coeluting analytes? Explain your
selection. (E ˆ‡0:43 V; E ˆ‡0:77 V.)

A B
9. Use the adsorption theory (of Section 2-1-3) to explain why adsorptive stripping
voltammetry results in nonlinear calibration plots.
10. Derive the Cottrell equation by combining Fick's ®rst law of diffusion with the
time-dependent change of the concentration gradient during a potential-step
experiment.