6. Potentiometric measurements at zero or impressed current

The indications of the various types of indicator electrodes are used either to directly relate the potential read to the concentration of the solute(s), thanks to prior calibration (potentiometric assays), or to determine a quantity of substance via a chemical reaction (potentiometric titrations).

Depending on the operating conditions, there are two main types of potentiometric measurement:

• a) Zero-current potentiometry, with one indicator electrode (and one reference electrode) or two indicator electrodes (generally of different types);

• b) Impressed current potentiometry, with one indicator electrode (and one reference electrode) or two indicator electrodes (usually of the same type).