Dynamic electrochemistry with ionophore based ion-selective membranes
This review outlines key principles and recent advances in the use of dynamic electrochemistry with polymeric liquid membranes. Ideally polarizable membranes are most attractive in fundamental studies of ion transfer and when the accumulation of the ion in the receiving phase is of key interest, for example in stripping ion transfer voltammetry. All solid-state membranes doped with conducting polymers have exhibited attractive low detection limit for hydrophilic ions. On the other hand, initially non-polarized interfaces are most useful when one aims to effect a concentration change of an ionic species in the sample phase. Conveniently, these types of membranes can be interrogated with potentiometry and sequentially with dynamic techniques such as chronopotentiometry. This can be used to obtain speciation information as they allow one, in principle, to assess total labile and free ion concentrations in the same experiment. A number of electrochemical techniques have been reported and include controlled potential techniques such as cyclic voltammetry, normal pulse voltammetry, stripping voltammetry and thin layer coulometry as well as current controlled ones such as pulsed chronopotentiometry and flash chronopotentiometry. All of these techniques have their purpose and strength.