Ag/AgCI electrodes

FIGURE 10.2 A schematic diagram of a combination glass pH electrode. A thin glass bulb with an inner Ag/AgCI electrode responds to pH changes in the test solution. A second Ag/AgCI in an outer jacket with a liquid junction serves the reference electrode for potentiometric measurement. An attached temperature probe is used to compensate for temperature effects. 

Ag/AgCI electrode containing aqueous electrolyte MCI2... 

Fig. 6.10 (a) Classical arrangement of ISE in which Ag/AgCI electrode is used as internal reference, (b) Ag/AgCI electrode with liquid junction for use as external reference electrode... 

The potential of the reference electrode clearly depends on the concentration of the internal solution. It is preferable to select the composition of the internal solution such that it matches the osmolality of the sample solution as much as possible in order to prevent flux of solvent through the junction. Values of reference electrode potentials for the Ag/AgCI electrode with different filling solutions are shown in Table 6.1. 

Screen printing is an excellent method for fabrication of ISEs on an industrial scale. Ag/AgCI electrodes can be screen printed onto a suitable support such as Kapton polyimide. The selective membrane is then printed onto the ISE, often with an intervening layer of a hydrogel such as poly(vinyl alcohol) soaked with NaCl solution to act as the internal reference solution. The reductions of cost associated with the mass-production of these electrodes allow them to be sold as single-use disposable devices. Also their small size relative to conventional ISEs allows them to be assembled into sensor arrays. 

Figure 6.5. Schematic diagram of a gas-sensing electrode. Selective ion electrode is shown as a glass electrode. The reference electrode is an Ag-AgCI electrode. Other electrode combinations are possible...

Fig. 7.22 The electrode assembly (plug B in Fig. 7.20) (P) a reference electrode (this is a 2.0 mm diameter Ag rod for an Ag/Ag electrode, or an Ag rod with an AgCI coating over the lowest 2 cm for an Ag/AgCI electrode, (Q) heat-shrunk Teflon tubing, (R) aqueous AgNOa (0.01 mol L for an Ag/Ag electrode) or KCI (4.0 mol L for an Ag/AgCI electrode), (S) a Vycor porous disc, (T) the working electrode (platinum wire), (U) the counter electrode (Platinum wire), and (V) neoprene O-rings.

The potential of the Ag/AgCi electrode is more negative than that of the SCE by... 

Fig. 3. Electrotaxis chamber and electric circuitry, (a) Chamber constructed in a plastic tissue culture dish, viewed from above, (b) Side view showing DC power supply, Ag/AgCI electrodes and agar-salt bridges that carry the voltage from the beakers to the two small medium reservoirs at the end of elecfrofaxis chamber. (Modified from (26)).

Figure 15.9 A commercial solid-state fluoride ISE. The ion-sensitive area is a solid crystal of LaFj doped with Eup2. The filling solution contains NaF and NaCI. The electrical connection is made by an Ag/AgCI electrode. ( Thermo Fisher Scientific (www.thermofisher.com). Used with permission.)...

Ag-AgCI electrodes are usually chosen (see Section 16.7 and Table 3-1). Care has to he taken that the electrical connection to the ship is sufficiently low resistance... 

TABLE 5.1. Response of Ag-AgCI Electrode to Interfering Halide Ions"... 

The absence of Baq and aA ci om the Nernst equation is explained in Sectiori 1.7 on the Ag/AgCI electrode. Note also that atm. 

The potential of such electrodes depends on the activity of a specific ion. The most widely used is the glass electrode. This consists of a tube ending in a special glass bulb filled with a O.IM HCI in which a Ag/AgCI electrode is inserted. The special glass is sensitive to H ions and is specific for pH measurements. A combined glass electrode is often used in which a calomel electrode is coupled with the glass electrode. The... 

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