Page 52 - Pharmaceutical Analytical Chemistry II - Pharm D- 02-06-07102
P. 52
INDICATOR ELECTRODES
Ideal Indicator electrode responses rapidly and reproducibly to
changes in the concentration of the analyte ion
Two classes of Indicator Electrodes
- Metallic indicator electrodes
- Membrane indicator electrodes
Metallic Electrodes
Types of Metallic indicator electrodes:
1. Electrodes of the zeroth kind (Redox inert electrodes)
2. Electrodes of the first kind
3. Electrode of the second kind
1- Redox inert electrodes:
An Inert metal, It has no share in redox reaction.
It responds to the potential of the redox system with which it is in
contact
Example: platinum (Pt), gold, palladium
Pt electrode immersed in a solution containing Ce4+/ Ce3+
E ind = E0Ce – 0.059 log [Ce3+] / [Ce4+]
( Application: Potentiometric titration using redox reaction)
2- Electrodes of the first kind: (for cations)
A metal in contact with a solution containing its own ion.
51
