Sodium electrode

Despite the high selectivity of sodium glass ISEs, problems arise in clinical use, and the contaminated membrane surfaces need special treatment at regular intervals (7,51). Polymeric membrane ISEs with ionophores (20) and (21) are less affected and permit sodium measurements in undiluted serum and urine (51). 

Some characteristic features of PVC sodium electrodes based on the acyclic ionophore (20) and the cyclic bis-12-crown-4 with aliphatic bridging (21) are compared with those of a glass electrode in Table 3.14. 

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The poor efficiencies of coal-fired power plants in 1896 (2.6 percent on average compared with over forty percent one hundred years later) prompted W. W. Jacques to invent the high temperature (500°C to 600°C [900°F to 1100°F]) fuel cell, and then build a lOO-cell battery to produce electricity from coal combustion. The battery operated intermittently for six months, but with diminishing performance, the carbon dioxide generated and present in the air reacted with and consumed its molten potassium hydroxide electrolyte. In 1910, E. Bauer substituted molten salts (e.g., carbonates, silicates, and borates) and used molten silver as the oxygen electrode. Numerous molten salt batteiy systems have since evolved to handle peak loads in electric power plants, and for electric vehicle propulsion. Of particular note is the sodium and nickel chloride couple in a molten chloroalumi-nate salt electrolyte for electric vehicle propulsion. One special feature is the use of a semi-permeable aluminum oxide ceramic separator to prevent lithium ions from diffusing to the sodium electrode, but still allow the opposing flow of sodium ions. 

The power of the ZEBRA cell depends on the resistance of the cell during discharge. The resistance of the ZEBRA cell rises with increasing depth of discharge (DOD). There is a contribution to the resistance from the fixed values of the solid metal components and of the/ "-alumina solid electrolyte. The variable parts of the resistance arc the sodium electrode and the positive electrode. The increase in internal resistance during discharge is almost entirely due to the positive electrode, as can be seen from Fig. 4. 

Sodium dodecylsulfate (SDS), 12 3, 13 744, 24 145, 154 adsorption of, 24 140 Sodium dodecyl sulfonate (SDSe), adsorption of, 24 141 Sodium electrodes... 

Tissue electrodes [2, 3, 4, 5, 45,57], In these biosensors, a thin layer of tissue is attached to the internal sensor. The enzymic reactions taking place in the tissue liberate products sensed by the internal sensor. In the glutamine electrode [5, 45], a thick layer (about 0.05 mm) of porcine liver is used and in the adenosine-5 -monophosphate electrode [4], a layer of rabbit muscle tissue. In both cases, the ammonia gas probe is the indicator electrode. Various types of enzyme, bacterial and tissue electrodes were compared [2]. In an adenosine electrode a mixture of cells obtained from the outer (mucosal) side of a mouse small intestine was used [3j. The stability of all these electrodes increases in the presence of sodium azide in the solution that prevents bacterial decomposition of the tissue. In an electrode specific for the antidiuretic hormone [57], toad bladder is placed over the membrane of a sodium-sensitive glass electrode. In the presence of the antidiuretic hormone, sodium ions are transported through the bladder and the sodium electrode response depends on the hormone concentration. 

It is found that in alkaline solutions (Ph > H for soft glass) the glass no longer functions as a hydrogen electrode but is affected by an alteration in the sodium ion concentration of the solution. With sodium amalgams, in fact, glass may serve as a sodium electrode of constant thermodynamic potential. 

In order to get the potential of the sodium electrode in aqueous 0.100M NaCl against a calomel electrode in the same solution, one measures the emfs of cells (1) and (2). Cell (1) is to measure the potential of the amalgam electrode (Na(Hg)) and cell (2) to measure the potential of the Na electrode against the Na(Hg) electrode. The sum of the emfs of the two cells (-3.113 V) corresponds to the emf of the hypothetical cell (3) and is equal to the potential of the Na electrode in the aqueous solution. 

The cell reactions are shown in Fig. 8.21, from which it can be seen that overdischarge and overcharge reactions are possible. Use is made of the overdischarge reaction to allow the assembly of the cell without the addition of elemental sodium. To the products of the discharge reaction - nickel and sodium chloride - is added a small quantity of aluminium which on the first charge generates enough excess sodium to prime the sodium electrode ... 

Other colloidal solids than NaX(s) and other electrolytes than NaCl may be present in the soil suspension, but they are assumed not to interfere with the performance of the electrode pair. The development of electrical potential at the sodium electrode is a somewhat complicated process that includes the creation... 

The emf developed by this double system is the algebraic sum of those developed by two calomel-sodium electrode pairs ... 

The sodium electrode [139] in molten sodium chloride is very reversible with an exchange current density that varies from about 100 A cm-2 at 820°C to about 200 A cur2 at 920°C. 

Metal insert Sodium electrode Solid electrolyte... 

Highly specific sodium electrodes have been developed in which the selectivity for sodium may be 10 times greater than that for potassium (C3, M19). With urine, the pH and potassium concentration should preferably be controlled, but this is unnecessary for blood. The potassium glass electrode is less selective and responds to NH/ and Na. Its selectivity may vary with age (M19). It can be used with blood only if corrections are made for sodium concentration according to Eq. (2) (M19, N2, N3), but when this is done, the electrode shows a linear response to potassium concentration. The precision of serum sodium and potassium measurements with electrodes was found to be better than those obtained by flame photometry (M19, N3). To compare the accuracy of the two methods, the results by flame photometry must be converted to concentrations in serum water. For most specimens, it was found that concentrations could be calculated satisfactorily from activity measurements and results by the two methods agreed (N3), but differences were noted with some samples. So far the cause of this has not been resolved, but it is possible that in future ionic activity will be recognized as a better diagnostic feature than ionic concentration (N3). 

The potentials at which electrons are generated in a liquid ammonia solution of sodium salts are also more positive than the reversible potential of the sodium electrode but in this system too the authors of Refs. and succeeded in realizing a reversible sodium electrode consisting of metallic sodium covered with a layer of beta-aluminate. The conductivity of the latter is due to sodium ions. 

Figure 9.6 On-line low-level measurements of sodium using the Orion ionplus 211 ILL on-line ion-selective sodium electrode (Reproduced by kind permission of Thermo Electron Corp).

Thus, it appears that the excitable membrane can be transformed from a potassium electrode to a sodium electrode during the active process (4). 

In confirmation of this hypothesis, we determined the concentration of calcium on the calcium electrode in a series of solutions with a constant concentration of sodium ion, using the sodium electrode as reference electrode. The calibration is carried out with 1 and 3 mM... 

Certain food and drug regulations regard all slow-release preparations as drugs and require their safety to be established prior to clinical application. Thus, a potassium ion-selective electrode has been employed to follow [416] the release parameters of 12 encapsulated potassium chloride tablets. Several of the tablets showed only medium dissolution rates for potassium and are unlikely to cause adverse effects such as gut ulceration. A sodium electrode has been similarly used to study the release of sodium phenobarbitone through a dialysis membrane into tris buffer [417]. Sodium in organic compounds has also been determined with an Orion 94-11 sodium electrode following combustion in a closed flask [418]. 

A very interesting analytical approach was chosen by Updike and Treichel [286] who constructed a tissue sensor for antidiuretic hormone (ADH) using a toad bladder tissue membrane over the surface of a sodium ion-sensing glass electrode. The measurement was based on the enhancement of sodium ion transport in the presence of ADH. The bladder membrane must be oriented with its mucosal side towards the sodium electrode because the transport occurs only from the mucosal to the serosal side. The ADH assay was very fast (response time about 10s) however, sodium transport was also affected by some other hormones and thus this method is not specific. 

Current is collected from this outer metal container (positive) and passes to the liquid sodium electrode (negative) through the external load. 

Kisza A, Kazmierczak J, Bprresen B, Haarberg GM, Tunold R (1995) The kinetics of the sodium electrode reaction in molten sodium chloride. J Electrochem Soc 142(4) 1035... 

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