Electrode potentiometric

Potcntiomctric Biosensors Potentiometric electrodes for the analysis of molecules of biochemical importance can be constructed in a fashion similar to that used for gas-sensing electrodes. The most common class of potentiometric biosensors are the so-called enzyme electrodes, in which an enzyme is trapped or immobilized at the surface of an ion-selective electrode. Reaction of the analyte with the enzyme produces a product whose concentration is monitored by the ion-selective electrode. Potentiometric biosensors have also been designed around other biologically active species, including antibodies, bacterial particles, tissue, and hormone receptors. 

One of the most fruitful uses of potentiometry in analytical chemistry is its application to titrimetry. Prior to this application, most titrations were carried out using colour-change indicators to signal the titration endpoint. A potentiometric titration (or indirect potentiometry) involves measurement of the potential of a suitable indicator electrode as a function of titrant volume. The information provided by a potentiometric titration is not the same as that obtained from a direct potentiometric measurement. As pointed out by Dick [473], there are advantages to potentiometric titration over direct potentiometry, despite the fact that the two techniques very often use the same type of electrodes. Potentiometric titrations provide data that are more reliable than data from titrations that use chemical indicators, but potentiometric titrations are more time-consuming. 

The results presented above show that with conveniently modified electrodes, potentiometric determinations of pan can be performed in aqueous-organic solvents at normal and subzero temperatures. In particular, it must be emphasized that these modified electrodes actually demonstrate the pH response theoretically expected. 

The existence of the nitryl ion in the presence of acidic substances suggested that nitrate ion in fused alkali nitrates might dissociate into N02+ and 0 2 ions (5). To determine the extent of the dissociation, it was necessary to develop an electrode potentiometrically responsive to either N02+ or 0 2. The only possibility for a reversible N02+ electrode that came to mind was nitrogen dioxide gas bubbling over platinum. This electrode did respond to N02+ in acidic solutions, but as ex-... 

Lvova et al. [100] Caffeine, catechines, sugar, amino acid L-arginine Natural coffee, black tea and different sorts of green teas Glucose oxidase/with glutaraldehyde and BSA, then covered with an aromatic polyurethane membrane Carbon paste screen-printed electrodes/ potentiometric (different active components on each of 30 sensors to construct an array) Iron hexacyanoferrate Prussian Blue, Fein[Fen(CN)6]3... 

Figure 4.3 Dual-polarized electrode potentiometric titration curves (a) titration of Fe(II) by Ce(TV) (b) titration of As(III) by I2.

Third-Generation Glucose Electrodes Potentiometric Urea Elearode... 

B6. Baum, G., Organic cation-selective electrode Potentiometric determination of acetylcholine activity. Anal. Lett. 3, 105-111 (1970). 

The order of presentation of the electroanalytical methods will be direct potentiometry with ion-selective electrodes, potentiometric titrations, voltammetry/polarography, polarisation titrations (amperometric and potentiometric), conductometry/coulometry and electrochemical detectors. 

Fe(III)/Fe(II). A pH 3.0 chloride solution equimolal in the two iron species was found to yield a Nemstian response down to 6x10 m total iron, corresponding to an exchange current of about IxIO amp cm. It appears that At pH 6.0 Fe(III) is too insoluble to influence a platinum electrode. Potentiometric and kinetic experiments with platinum in Fe(II) solutions at pH 6.0 indicated the formation of a passivating layer, in agreement with Doyle (17). 

Amperometric electrodes Potentiometric electrodes Coulometric electrodes ISFET... 

All titrimetric methods of analysis require some means of detecting the equivalence point. This could be an abrupt change of color (colorimetric titrations), a sudden change in the potential difference between two electrodes (potentiometric titrations), a change in current flow through two electrodes (amperometric titrations), and so on. Similarly, the radioactivity of either the titrant or the substance titrated can be employed for detecting the equivalence point. This type of analysis is called radio-metric titration. It should be noted that the sole purpose of the radioactivity is to signal attainment of the equivalence point and that it takes no part in the titration process. The technique can be employed in all classes of titrations, provided that a phase separation can be effected. 

Amperometric electrode instruments, nonenzyme electrodes, amperometric enzyme electrodes, potentiometric enzyme electrodes Various CO2 gas sensors... 

After elution from the column, the eluate carrying the concentrate zone may either be transported directly to the detector or be further processed to produce a detectable species before being transponed to the detector. The former case refer to systems where the analyte can be determined without transformation, e.g. in AAS. ICPES or selective electrode potentiometric measurements. The latter category include most applications in spectrophotometry, fluorimetiy and chemilumine.scence, which usually require a post column reaction. In both cases, minimization of dispersion in the conduits between the column and detector is essential for obtaining better enrichment factors. 

In contrast with amperometric electrodes, potentiometric electrodes are passive in that they do not convert the analyte. The main use of potentiometry is to measure the concentration (strictly activity) of a target analyte and so it is usefiil to revisit the Nemst equation, relating the cell potential to activity. For this purpose, consider a simple redox reaction at the right-hand electrode of a cell, with SHE as the left-hand electrode. The process at the right-hand electrode is... 

Glucose Saccharomyces cerevisiae Oxygen electrode, potentiometric... 

Electrode type PQQ EAD Cu + Amperometric electrodes Potentiometric electrodes... 

Precise measurements were impossible due to failure to prepare truly reversible electrodes. Potentiometric titrations have, however, been successfully carried out in solutions of anhydrous arsenic (III) chloride employing silver-silver chloride electrodes . 

Amperometric Gas-sensing electrode Potentiometric Potentiometric Ammonia gas-sensitive semiconductor... 

Potentiometric detection is based on the detection of a membrane potential across the membrane of a probe electrode. Potentiometric probes measure a membrane potential linearly dependent on the logarithm of the activity of a primary ion. Experimentally, a typical setup would be... 

Among the different methods used to detect the catalysis of an analyte by the immobilized en me, the electrochemical method has been the most extensively investigated. The analyte can be detected either from the potential measurement between the modified electrode and a reference electrode (potentiometric method) or from the measurement of current crossing the modified electrode when a potential is applied (amperometric method). Based on kinetic considerations, amperometric biosensors are largely... 

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