potentiometrische

Potentiometric methods refer to a class of analytical techniques used to measure the concentration of ions in a solution by determining the electromotive force (EMF) of a galvanic cell. These methods rely on the principle that the potential difference between two electrodes is proportional to the logarithm of the ion activity in a solution, as described by the Nernst equation. The term "potentiometric" derives from "potential," reflecting the core measurement of electrical potential rather than current flow, which distinguishes it from voltammetric techniques.

A potentiometric measurement typically involves two electrodes: a reference electrode with a stable, known potential and a selective electrode that responds to the analyte of interest. Common selective electrodes include glass pH electrodes for hydrogen ions, ion-selective electrodes (ISEs) for cations like sodium or potassium, and specialized sensors for other ions or molecules. The potential difference between these electrodes is measured using a high-impedance voltmeter, ensuring no current flows and avoiding electrode polarization.

Potentiometric titrations are a specialized application where the endpoint of a titration is determined by monitoring the potential change as reactants are added. This method is widely used for acid-base, redox, and precipitation titrations, offering high precision and sensitivity. The technique is particularly valuable for weak acids or bases, where indicators may be ineffective.

Potentiometric methods are favored for their simplicity, speed, and ability to measure low concentrations without sample destruction. They are widely used in clinical chemistry, environmental monitoring, food analysis, and industrial quality control. However, they require careful calibration, proper handling of electrodes, and consideration of factors like temperature, ionic strength, and interfering ions to ensure accurate results.