ETH 157, also known as Sodium ionophore II, is primarily used in research and analytical chemistry for its ability to selectively transport sodium ions across membranes. It is often employed in ion-selective electrodes (ISEs) to measure sodium ion concentrations in various solutions, making it valuable in environmental monitoring, biomedical research, and clinical diagnostics. Additionally, ETH 157 is utilized in studies involving ion transport mechanisms and membrane physiology, helping scientists understand cellular processes and ion dynamics. Its specificity for sodium ions also makes it a useful tool in synthetic chemistry for creating sodium-selective sensors and probes.