Amperometric Ion-Selective Electrode for Alkali Metal Cations Based on a Room-Temperature Ionic Liquid Membrane

Cyclic voltammetry is used to study the transfer of a series of cations and anions across a room-temperature ionic liquid membrane composed of tridodecylmethylammonium cation and tetrakis[3,5-bis(trifluoromethyl) phenyl]borate anion. It is shown that the addition of water-soluble crown ether(e.g. 18-crown-6) to the aqueous phase makes it possible to distinguish the voltammetric responses of alkali and alkaline earth metal cations. The determination of low concentrations of K+ (0.05-0.3 mM) in the presence of an excess of Mg2+ (1 mM) in water is demonstrated as a model application of an amperometric ion-selective electrode for K+.