Aqueous phases, distribution potential, ITIE

First, when only one ionic species can be distributed between the phases, there is a contact equilibrium [23] at the interface and the potential difference is completely determined by the standard ion transfer potential of this potential-determining ion. In actual cases, however, this contact equilibrium is seldom achieved at the ITIES, since the transfer of counter ions of the potential-determining ion across the interface is not always negligible. If a distribution equilibrium is established t the reference ITIES, the degree of interference can be estimated using Eq. (3). However, the distribution equilibrium is not usually realized in an actual reference ITIES. Rather, the final equilibrium, if achieved, would nullify the potential difference between the two aqueous phases. Consider the following example ... 

A reference electrode which can directly be dipped in the organic phase is not available, except the AgPh4B/Ag electrode [44]. It is customary to use a nonpolarized liquid-liquid interface, i.e., a reference ITIES. The potential drop across this interface is primarily determined by an ionic species distributed commonly in both aqueous and organic phases. There are two points to be taken into account in using this reference ITIES the deviation from nernstian behavior and limited reversibility. 

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