Ion selective electrode is a kind of electrochemical sensor that uses membrane potential to measure theactivity or concentration of ions in the solution. When it comes into contact with the solution containing the ions which are to be measured, it will generate contact with the sensor at the interface between its sensitive membrane and the solution. Ion activity is directly related to membrane potential. Ion selective electrodes are also called membrane electrodes. This type of electrode has a special electrode membrane that selectively responds to specific ions. The relationship between the potential of the electrode membrane and the ion content to be measured conforms to the Nernst formula. This type of electrode has the characteristics of good selectivity and short equilibrium time, making it the most commonly used indicator electrode for potential analysis.