Potentiometry liquid membrane-based

The previous chapters dealt with ISE systems at zero current, i.e. at equilibrium or steady-state. The properties of the interface between two immiscible electrolyte solutions (ITIES), described in sections 2.4 and 2.5, will now be used to describe a dynamic method based on the passage of electrical current across ITIES. Voltammetry at ITIES (for a survey see [3, 8, 9, 10, 11, 12,18]) is an inverse analogue of potentiometry with liquid-membrane ISEs and thus forms a suitable conclusion to this book. 

Nonselective, metallic indicator electrodes have been used for potentiometric measurements in complex biological media, for example, Pt electrodes have been used to monitor the redox potential of fermentation broths as cultures grow [17]. However, zero-current potentiometry more often involves ISEs based on solid membranes, composed of a sparingly soluble salt of the ion of interest or liquid membranes, in which an ion-selective reagent is dissolved, with the membrane separating reference... 

Non-equilibrium processes at the sample/membrane interface and across the bulk membrane bias the selectivity and detection limits of the electrodes. Elimination of these nonequilibrium effects by operating the electrodes under complete equilibrium conditions will be of both practical and fundamental significance. While non-equilibrium responses are useful for potentiometric polyion-selective electrodes, it is not obvious whether potentiometry based on mixed ion-transfer potentials is a better transduction mechanism than amperome-try/voltammetry based on selective polyion transfer (65, 66). Ion-transfer electrochemistry at polarized liquid/liquid interfaces is introduced in Chapter 17 of this handbook. 

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