Page 185 - Analytical Electrochemistry 2d Ed - Jospeh Wang

170 POTENTIOMETRY

6. Describe the response mechanism of the ¯uoride ion-selective electrode.
Explain clearly why the OH is the major interfering ion in F ISE measure-
ments.
7. Discuss the signi®cance of the selectivity coef®cient of an ISE. How would you
determine its value?

8. Give example of a successful ISE for measuring a macromolecular polyanionic
compound.
9. Use the Nikolskii±Eisenman equation to explain why lowering of the detection
limits requires careful attention to the selectivity of the resulting ISE.
10. Explain clearly how the presence of magnesium ion can in¯uence the response
of the calcium ISE.
11. By how many millivolts will the potential of a calcium ISE change if the
electrode is removed from a 1 10 3 M CaCl 2 solution and placed in
1 10 3 M CaCl 2 ?
12. Explain clearly why small uncertainties in the measured cell potential can cause
large errors in the response of ISEs.
13. Discuss the major sources of errors in potentiometric measurements.