Sensors, for ion solvation

Various potentiometric indicator electrodes work as sensors for ion solvation. Metal and metal amalgam electrodes, in principle, respond in a thermodynamic way to the solvation energy of the relevant metal ions. Some ion-selective electrodes can also respond almost thermodynamically to the solvation energies of the ions to which they are sensitive. Thus, the main difficulty in the potentiometric study of ion solvation arises from having to compare the potentials in different solvents, even though there is no thermodynamic way of doing it. In order to overcome this difficulty, we have to employ a method based on an extra-thermodynamic assumption. For example, we can use (1) or (2) below ... 

Ion solvation has been studied extensively by potentiometry [28, 31]. Among the potentiometric indicator electrodes used as sensors for ion solvation are metal and metal amalgam electrodes for the relevant metal ions, pH glass electrodes and pH-ISFETs for H+ (see Fig. 6.8), univalent cation-sensitive glass electrodes for alkali metal ions, a CuS solid-membrane electrode for Cu2+, an LaF3-based fluoride electrode for l , and some other ISEs. So far, method (2) has been employed most often. The advantage of potentiometry is that the number and the variety of target ions increase by the use of ISEs. 

The sensor for ion solvation was a silver wire for Ag+ and an univalent cation-sensitive glass electrode for Li+ and Na+. In detennining AG (M+, R -> S) from Eq. (6.13), they assumed that the LJPs at PC/(PC + DMSO) and PC/DMSO were negligible (Ej = 0). At the same time, they detennined in PC the step-wise formation constants (/ ) for the complexation of Ag+, Li+ and Na+ with DMSO (see Section 6.3.3), and used them to calculate the Gibbs energies of transfer of those ions from PC to (PC + DMSO) and to neat DMSO. Equations (6.14) and (6.15) were used in the calculation ... 

---

See also in sourсe #XX -- [ ]

---