An electrode that can seek out sulfate anions has been developed - with the help of ionic liquids - by chemists in Spain. 

Ramón Martinez Ma n ez and colleagues at the University of Valencia incorporated ionic liquids (which have both positively charged organic and negatively charged inorganic components) and ionophores that facilitate ion movement, into PVC membranes.   

Martinez Ma n ez carefully chose the ionic liquid and ionophore, and made an ion-selective electrode that was remarkably selective to sulfate anions.   

The tendency of an anion to enter a membrane is a balance between two energies; one from anion-membrane interactions and the other from the anion-water interaction. 

In Martinez Ma n ez's electrode the ionic liquid decreases the difference in the dielectric constant between the membrane and the water. At the same time the ionophore forms a strong interaction with the detected anion. 

Ion-selective electrodes are useful devices for detecting chemicals quickly and accurately, even at low concentrations. Anion detection has been problematic until now because they are often soluble in water.   

Lorna Jack