Electrode response

In many experiments a noncarbon-base anion-responsive electrode, silver-silver chloride, was employed. This electrode was selected for pairing with cation-responsive carbon-based electrodes because of its known properties and ease of preparation. 

All dispersions deposited on Dacron felt. Silver-silver chloride was anion-responsive electrode. 

Cell DC-2. Earlier demineralization studies by Lyon (9) employed cell DC-2. This was a sandwich-type cell with Lucite side plates bolted together with two epoxy resin-gasketed graphite electrodes separated by an anion-permeable membrane. The membrane was necessary because a suitable anion-responsive electrode was not then known. The principle of operation is that in the cathode compartment, after several current reversal conditioning cycles, sodium ions are removed by the cathode while chloride ions migrate from the cathode through the membrane to the anion chamber. In the anode chamber, sodium ions, from the previous half cycles, are rejected from the anode. The net result was salt depletion in the cathode chamber and a similar concentration increase in the anode chamber. 

After the feasibility of demineralization with coupled cation- and anion-responsive electrodes had been established, it became possible to dispense with the membrane no further experiments were planned with DC-2. 

Immobilization method Technique Response Electrode References... 

On-board type oil deterioration pH sensor. Considering practical use as an on-board type pH sensor, it is desirable to use rigid materials for the electrodes which are thought not to be damaged due to mechanical vibrations of the engine. Therefore, oxidized stainless steel and lead electrode were selected as the pH-response electrode and the reference electrode, respectively. The signal of the newly developed sensor gradually increases as the deterioration of the oil... 

A cation-responsive electrode can associate cations with chemical bonds therefore, its cation capacity is always higher than its anion capacity. In this case, the total capacity is limited solely by the anion capacity. On the other hand, the total capacity of an anion-responsive electrode is limited by its cation capacity. 

Most pH determinations are made by electrometric methods, the pH of the unkown solution (X) being calculated from that of a known standard (S) and the emf ( x and s) of a cell composed of a hydrogen ion-responsive electrode (for example, a glass electrode or a hydrogen gas electrode) coupled with a reference electrode (calomel, silver-silver chloride). This cell is filled successively with the standard solution S and with the unknown solution X. A liquid junction potential j exists where these solutions make contact with the concentrated KCl solution of the reference electrode. From the Nernst equation for the cell reactions and assuming an ideal hydrogen ion response ... 

These contain redox-active centers able to switch on/off cation or anion complexation when treated with redox reagents or electrochemical stimulation. Examples include some ferrocenyl-containing macrocycles, such as (159), or donors with an anthraquinone fragment, as in (160).252 The functionalization of electroactive polymers by monocyclic polyethers has been used for the building of cation-responsive electrodes. 

If the electrode is in a solution containing a mixture of cations (or anions, if it is an anion-responsive electrode), it may respond to the other cations. Suppose, for example, we have a mixture of sodium and potassium ions and an electrode that responds to both. The Nemst equation must include an additive term for the potassium activity ... 

Even univalent ions can be sequestered, and part of the Na" " in living animal tissue is in an osmotically inactive form. It is held by polymers whose repeating units carry at least one acidic group (examples nucleic acids, mucopolysaccharides). These sequestered sodium ions can instantly be liberated by ions of a higher valency, and the concentration measured with a sodium-responsive electrode (Palaty, 1966). 

In the case of a gas phase with plug flow, the area between the curves is inversely proportional to /cl U (cf. Fig. 3.16). In all cases, fast response electrodes, if available, should be used k /cl which minimizes distortions in measuring OTR. 

Figure 3.3 Surfactant-responsive electrode based on a silver-silver chloride electrode (reproduced by kind permission of the Society for Chemical Industry).

The Society for Chemical Industry for permission to reproduce (with slight modification) the diagram of a surfactant-responsive electrode (Figure 3.3) from Chapter 2 of Recent Developments in the Analysis of Surfactants (ed. Porter, M. R.), published for the SCI by Elsevier Applied Science, London, 1991. 

These electrodes are mainly anion responsive and several varieties are available for measuring the halide ion concentrations. The ion responsive material for such halide response electrodes is usually a silver halide. 

S. Shibata, M.P. Sumina, A. Yamada, (1985). An improved heat-responsive electrode for... 

Bishop, E. and Dhaneshwar, R. G., 1963, Silver- and halide-ion responsive electrodes. Analyst 88 424-445. 

Analytical pH of process stream Commonly used in effluents. Standard equipment available through robust pH responsive electrodes such as antimony, platinum, tungsten can be preferable to glass electrodes. Solid A AgCI is a useful reference electrode Frequent... 

Coetzee, C. J., Preiser, H., Anion-responsive electrodes based on ion association extraction systems. Ana/... 

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