Phase boundary potential model

Pungor E (1998) The theory of Ion Selective Electrodes. Anal Sci 14 249-256 Bakker E, Buhlmann P, Pretsch E (2004) The phase-boundary potential model. Talanta 63 3-20... 

The Nikolsky-Eisenman equation and phase boundary potential model... 

Besides hydrophobicity of ions and stability of their ionophore complexes, the concentration and charge of the ionic sites in the membrane phase also affect the ion selectivity of ionophore-based ISEs. This effect was first found for neutral-ionophore-based ISEs (14, 43), then for charge-ionophore-based ISEs (10, 33), and most recently implemented in an equilibrium phase boundary potential model generalized for both systems with primary and interfering ions of any charges and their complexes of any stoichiometries (34). 

More recently, a generalized phase boundary potential model that describes apparently non-Nemstian equilibrium responses of ionophore-based ISEs was developed (46). The model predicts that ionophore-based ISEs can give three types of apparently non-Nemstian... 

The non-equilibrium ion-exchange processes can cause deviation of the potentiometric responses from those predicted by the Nikolsky-Eisenman equation and the equilibrium phase boundary potential model. 

Effects of the transmembrane flux on the detection limits were also studied theoretically (60). The phase boundary potential model in mixed ion solutions as discussed in Section 7.3.1 was extended by implementing the steady-state transmembrane flux to demonstrate that the detection limit of a highly selective electrode, Cj (DL), is given approximately as... 

On the other hand, the Nernst-Planck theory is required for describing time- and space-dependent phenomena, for which the phase-boundary potential model is not suitable. - It is adequate for treating zero-current or dc experiments as well as inflnences of convection, flow, or stirring. 

While the phase-boundary potential model perfectly describes the response of macroscopic electrodes even in the presence of any number of mono-, di-, and trivalent ions, more involved models are required if other membrane properties are of interest such as concentration profiles in the membrane or transient responses. 

Bakker, E. 2010. Generalized selectivity description for polymeric ion-selective electrodes based on the phase boundary potential model. J. Electroanal. Chem. 639 1-7. 

Amemiya S, Buhlmann P, Umezawa Y (1998) A phase boundary potential model for apparently Twice-Nemstian responses of liquid membrane ion-selective electrodes. Anal Chem 70 445 54... 

The availability of thermodynamically reliable quantities at liquid interfaces is advantageous as a reference in examining data obtained by other surface specific techniques. The model-independent solid information about thermodynamics of adsorption can be used as a norm in microscopic interpretation and understanding of currently available surface specific experimental techniques and theoretical approaches such as molecular dynamics simulations. This chapter will focus on the adsorption at the polarized liquid-liquid interfaces, which enable us to externally control the phase-boundary potential, providing an additional degree of freedom in studying the adsorption of electrified interfaces. A main emphasis will be on some aspects that have not been fully dealt with in previous reviews and monographs [8-21]. 

Comparison of the calculated and observed changes in the EMF is shown in Table 1. It can be seen that the calculated changes in the phase boundary potential of membranes with 1.0 mM 1-3 in contact with 0.1 and 0.01 M aqueous KCl or RbCl were in good agreement with the corresponding observed values. Such an agreement indicates that it is reasonable to apply the present surface model to explain that the phase boundary potential is, in fact, determined by the amount of the primary cation permeated into or released out of the membrane side of the interface. 

The theory of ion-selective electrode response is well developed, due to the works of Eisenman, Buck and others [23], Three models used for the description of the ISE response through the years, namely kinetic, membrane surface (or space charge) and phase boundary potential (PBP) models, although being seemingly contradictory, give similar results in most cases [7], The first two sophisticated models are out of the scope of the present chapter, as the PBP model, despite its simplicity, satisfactorily explains most of the experimental results and thus has become widely applicable. The... 

PBP model considers the membrane potential as a sum of the potentials formed at the membrane-solution interfaces (phase boundary potentials), and generally neglects any diffusion potential within the membrane ... 

FIGURE 7.1. Dependence of surface coverage on phase-boundary potential (a) and corresponding depression of interfacial tension (b) for absorption modelled by Frumkin isotherm at two values of interaction parameters (o = 1.0 (curve 1) and 2.0 (curve 2). Adapted from Figure 1 in Ref. [15]. 

The concept of the electrochemical instability has been illustrated using a simple model for the coupling of the adsorption and partition of surface-active ions. Three main features of the electrochemical instability, that is, (1) the location of the instability in the values of the phase-boundary potential, (2) the existence of a window-like instability... 

In the proposed model, the phase boundary potential Eh can be expressed as... 

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