system. The study of ions crossing the immiscible liquid/liquid interface was first described by Nernst and Riesenfeld in 1902 . In the 1970s, Koryta et al. demonstrated that the faradaic and non-faradaic processes at the liquid/liquid interfaces are analogous to the ones at the solution/metal interface and therefore the same experimental methodology can be used. Thus various electrochemical techniques, including chronoamperometry , cyclic voltammetry 10 , stripping voltammetry and impedance measurements have been applied to study the electrochemical processes on liquid/liquid interface. At the same time, it was discovered that the interactions between the ionophore and the analyte (which are the basis of ISE operation) can be studied through voltammetry at the two immiscible liquids. The transport of ions across the liquid-liquid interface was compared to the transport of ions from the aqueous solution of the sample to the plasticized ISE membrane.