Potentiometry is one of the most often applied methods of instrumental analysis. In potentiometry, two electrodes are employed in a measuring cell, and the electric potential difference between them is measured, and used as an analytical signal for evaluation. In zero current potentiometry, two different kinds of galvanic measurement cells are used. Two important properties of direct potentiometry are: the dynamic concentration range and the accuracy. Titrimetric methods with potentiometric end point location can be applied when an electrode with the needed selectivity is not available. The selectivity of ion‐selective electrodes (ISEs) is an important feature. Several methods have been proposed for the experimental determination of ion‐selectivity coefficient. They can be listed in two groups: separate solution methods and mixed solution methods. The most frequently applied potentiometric measurements involve the determination and adjustment of the pH of different solutions, samples, reagents, reaction media, or buffers.