Which ion-selective electrode's selectivity is enhanced by valinomycin?

Valinomycin is a polyether antibiotic that is known for its ability to selectively bind potassium ions. Its mechanism of action involves the formation of a complex with potassium, which facilitates the movement of potassium through lipid membranes. This characteristic makes valinomycin particularly effective in enhancing the selectivity of ion-selective electrodes specifically designed for potassium measurement.

When incorporated into a potassium ion-selective electrode, valinomycin significantly increases the electrode's sensitivity and selectivity toward potassium ions over other cations. This is because the binding affinity of valinomycin for potassium is much higher than for other ions like sodium, calcium, or magnesium. As a result, when measuring potassium in a sample containing multiple ions, the electrode responds primarily to the potassium concentration due to the protective and selective nature of valinomycin’s interaction with these ions.

Consequently, valinomycin is commonly utilized within potassium-sensitive electrodes to improve their performance in various analytical applications, particularly in clinical and physiological contexts where accurate potassium measurement is crucial.