قطب كهربائي انتقائي للأيونات

The measurement principle of ion-selective electrodes (ISEs) is based on the relationship between the activity and concentration of ions in an electrolyte solution. An ISE typically consists of two electrodes: a working electrode and a reference electrode. The working electrode selectively responds to the target ion, while the reference electrode provides a stable potential as a reference.

The working electrode is usually coated with a selective membrane that exhibits a specific response to a particular ion. When the target ion interacts with the selective membrane, a change in electric potential is generated. By measuring this potential change, the concentration of the ion can be determined.

where:

• Z — ionic charge number;
• “±” — “+” for cations and “–” for anions;
• a — activity of the measured ion.