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 corresponds to the ion activity, allowing for precise analysis of substances like sodium, potassium, or chloride ions. ISEs are widely used in various fields, including environmental monitoring, clinical diagnostics, and food quality control. The construction of an ISE typically involves a selective membrane that responds to the target ion while remaining unaffected by others. This selectivity is crucial for accurate measurements. ISEs can be portable and easy to use, making them valuable tools in laboratories and fieldwork.