Dual-polarized amperometric endpoint

For this titration the dual-polarized amperometric endpoint detection system provides good sensitivity and rapid response. 

Because the generator electrodes must have a significant voltage applied across them to produce a constant current, the placement of the indicator electrodes (especially if a potentiometric detection system is to be used) is critical to avoid induced responses from the generator electrodes. Their placement should be adjusted such that both the indicator electrode and the reference electrode occupy positions on an equal potential contour. When dual-polarized amperometric electrodes are used, similar care is desirable in their placement to avoid interference from the electrolysis electrodes. These two considerations have prompted the use of visual or spectrophotometric endpoint detection in some applications of coulometric titrations. 

Figure 4.9 Coulometric titration cell with generator [II (generator anode, 0.7 x 0.7 cm)] and isolated auxiliary [I (generator cathode, 0.7 x 0.7 cm)] electrodes on the left side and a pair of identical platinum electrodes [III, IV (1.4 x 1.8 cm and 2.5 X 1.8 cm)] on the right for dual-polarized electrode amperometric endpoint detection.

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