potencjometry

Potenciometry, also known as potentiometry, is a branch of electrochemistry and analytical chemistry that focuses on measuring electric potential to determine properties of a chemical system. In potentiometric measurements, the potential difference between a working (indicator) electrode and a reference electrode is recorded under near-zero current, so the sample is not consumed and the electrode potential reflects the activity of a specific ion.

The measurement relies on the relation between electrode potential and ion activity, described by the Nernst equation. For a reversible electrode, the observed potential varies with the activity (or effective concentration) of the target ion. Potentiometric sensors often use ion-selective electrodes, such as glass electrodes for hydrogen ions (pH measurement) or solid-state and liquid-junction ion-selective sensors for other ions. A stable reference electrode provides a known potential, enabling a measurable difference that correlates with ion activity.

Typical configurations include a two-electrode arrangement with a reference electrode and an ion-selective or glass electrode, and sometimes a three-electrode setup that includes a counter electrode in electrochemical work. Modern high-impedance voltmeters minimize current, maintaining quasi-equilibrium conditions at the electrode interfaces.

Applications of potentiometry include rapid pH determination, monitoring of electrolytes, and quantification of specific ions in environmental, clinical, and industrial samples. Calibration against standards or standard additions is commonly used to relate measured potentials to ion activities or concentrations. Advantages of potentiometry are simplicity, speed, and non-destructive analysis, while limitations include drift, temperature sensitivity, and selectivity constraints, necessitating careful calibration and, in some cases, temperature control.