An ion-selective electrode (ISE) is a type of sensor used to measure the concentration of specific ions in a solution. It works by generating a voltage that is proportional to the activity of the target ion, allowing for precise measurements. ISEs are commonly used in various fields, including environmental monitoring, clinical diagnostics, and food safety. The construction of an ISE typically involves a membrane that selectively interacts with the ion of interest, such as sodium, potassium, or chloride. This membrane can be made from various materials, including glass or polymer, depending on the specific ion being measured.