Potentiometric sensors, use

FIGURE 2.11 Example of biplot. The scores (filled symbols) are replicates of analyses of wine samples of three vintages (2004, 2005, and 2006, respectively), while the loadings (stars) represent the potentiometric sensors used for the measurements (A = anion-sensitive sensors, C = cation-sensitive sensors, G = redox-sensitive sensors, pH = pH sensor) (reproduced from Rudnitskaya etal. 2009b, with permission). 

Schoening MJ, Ronkel E, Crott M et al (1997) Miniaturization of potentiometric sensors using porous silicon microtechnology. Electrochim Acta 42 3185-3193... 

Another interface that needs to be mentioned in the context of polarized interfaces is the interface between the insulator and the electrolyte. It has been proposed as a means for realization of adsorption-based potentiometric sensors using Teflon, polyethylene, and other hydrophobic polymers of low dielectric constant Z>2, which can serve as the substrates for immobilized charged biomolecules. This type of interface happens also to be the largest area interface on this planet the interface between air (insulator) and sea water (electrolyte). This interface behaves differently from the one found in a typical metal-electrolyte electrode. When an ion approaches such an interface from an aqueous solution (dielectric constant Di) an image charge is formed in the insulator. In other words, the interface acts as an electrostatic mirror. The two charges repel each other, due to the low dielectric constant (Williams, 1975). This repulsion is called the Born repulsion H, and it is given by (5.10). 

Owing to their specificity, sensitivity, and range of measurable concentrations, potentiometric sensors based on ionic or enzymatic selectivity have wide application in analytical determinations. Other potentiometric sensors using electrodes of the first kind (Mn+ M), used in precipation titrations, are not easy to manipulate and redox electrodes have a reduced application owing to their lack of selectivity, reacting to any oxidizable or reducible species. 

Varamban, S.V., Ganesan, R. and Periaswami, G. (2005) Simultaneous measurement of emf and short circuit current for a potentiometric sensor using perturbation technique. Sens. Actuators B, 104 (1), 94-102. 

Hibino, T, Hashimoto, A., Kakimoto, S. and Sano, M. (2001) Zirconia-based potentiometric sensors using metal oxide electrodes for detection of hydrocarbons. J. Electrochem. Soc., 148 (1), Hl-5. 

Guinovart, T., Parrilla, M., Crespo, G.A., Rius, F.X., Andrade, FJ., 2013. Potentiometric sensors using cotton yams, carbon nanotubes and polymeric membranes. Analyst 138 (18), 5208-5215. http //dx.doi.org/10.1039/C3 AN00710C. 

M. Javanbakht, S.E. Fard, A. Mohammadi, M. Abdouss, M.R. Ganjali, P Norouzi and L. Safaraliee, Molecularly imprinted polymer based potentiometric sensor for the determination of hydroxyzine in tablets and biological fluids. Anal. Chim. Acta, 612 (1) 65-74,2008. M. Javanbakht, S.E. Fard, M. Abdouss, A. Mohammadi, M.R. Ganjali, R Norouzi and L. Safaraliee, A biomimetic potentiometric sensor using molecularly imprinted polymer for the cetirizine assay in tablets and biological fluids, Electroanalysis, 20 (18) 2023-2030, 2008. 

Miura N, Lu G, Yamazoe N (1997) Zuctmia-based potentiometric sensor using a pair of oxide electrodes for selective detectimi of carbon monoxide. J Electrochem Soc 144 L198-L200... 

Amperometry is a voltammetric method in which a constant potential is applied to the electrode and the resulting current is measured. Amperometry is most often used in the construction of chemical sensors that, as with potentiometric sensors, are used for the quantitative analysis of single analytes. One important example, for instance, is the Clark O2 electrode, which responds to the concentration of dissolved O2 in solutions such as blood and water. 

Selig, W. S. Potentiometric Titrations Using Pencil and Graphite Sensors, /. Chem. Educ. 1984, 61, 80-81. 

More recendy, two different types of nonglass pH electrodes have been described which have shown excellent pH-response behavior. In the neutral-carrier, ion-selective electrode type of potentiometric sensor, synthetic organic ionophores, selective for hydrogen ions, are immobilized in polymeric membranes (see Membrane technology) (9). These membranes are then used in more-or-less classical glass pH electrode configurations. 

By using different membranes, it is possible to obtain potentiometric sensors for gases such as sulfur dioxide or nitrogen dioxide. Such sensors employ similar (acid-base) or other equilibrium processes. These devices, along with their equilibrium processes and internal electrodes, are summarized in Table 6-2. Membrane coverage... 

Ion-selective electrodes are membrane systems used as potentiometric sensors for various ions. In contrast to ion-exchanger membranes, they contain a compact (homogeneous or heterogeneous) membrane with either fixed (solid or glassy) or mobile (liquid) ion-exchanger sites. 

Dill K., Song J.H., Blomdahl J.A., Olson J.D., Rapid, sensitive and specific detection of whole cells and spores using the light-addressable potentiometric sensor, J. Biochem. Biophys. Meth. 1997 3 161-166. 

Uithoven K.A., Schmidt J.C., Ballman M.E., Rapid identification of biological warfare agents using an instrument employing a light addressable potentiometric sensor and a flow-through immunofiltration-enzyme assay system, Biosens. Bioelectron. 2000, 14 761-770. 

Detection of Li+ in artificial serum with a voltammetric Li-selective electrode in a flowthrough system was demonstrated [64], Lithium salts such as lithium carbonate have been extensively used for treatment of manic depressive and hyperthyroidism disorders. The therapeutic range of Li concentration is generally accepted to be 0.5-1.5mM in blood serum. The authors used normal pulse voltammetry in which a stripping potential was applied between pulses in order to renew the membrane surface and expel all of the extracted ions from the membrane, similar to galvanostatically controlled potentiometric sensors described above. Unfortunately, the insufficient selectivity... 

Although a few amperometric pH sensors are reported [32], most pH electrodes are potentiometric sensors. Among various potentiometric pH sensors, conventional glass pH electrodes are widely used and the pH value measured using a glass electrode is often considered as a gold standard in the development and calibration of other novel pH sensors in vivo and in vitro [33], Other pH electrodes, such as metal/metal oxide and ISFETs have received more and more attention in recent years due to their robustness, fast response, all-solid format and capability for miniaturization. Potentiometric microelectrodes for pH measurements will be the focus of this chapter. 

Another problem that is common for all membrane-based solid-state sensors is the ill-defined membrane-metal interface. A large exchange current density is required to produce a reversible interface for a stable potentiometric sensor response. One approach to improving this interface is to use conducting polymers. Conducting polymers are electroactive n-conjugated polymers with mixed ionic and electronic conductivity. They... 

Besides, potentiometric sensors with ion-selective ionophores in modified poly(vinyl chloride) (PVC) have been used to detect analytes from human serum [128], Cellular respiration and acidification due to the activity of the cells has been measured with CMOS ISFETS [129], Some potentiometric methods employ gas-sensing electrodes for NH3 (for deaminase reactions) and C02 (for decarboxylase reactions). Ion-selective electrodes have also been used to quantitate penicillin, since the penicillinase reaction may be mediated with I or GST. 

Besides these potentiometric sensors there are also amperometric sensors using the principle of ion conductive solid electrolytes. In addition to the heating voltage those sensors are also equipped with a second voltage supply, inducing a current, which varies depending on the concentration of the test gas. Fig. 3.19 shows a schematic view of these so-called saturating current probe. 

As far as the use of ferrocene molecules as potentiometric sensors is concerned, they are part of the more general reactivity pattern illustrated in Scheme 12. 

Enzyme electrodes with amperometric indication have certain advantages over potentiometric sensors, chiefly because the product of the enzymic reaction is consumed at the electrode and thus the response time is decreased. For this reason, the potentiometric glucose enzyme electrode, based on reaction (8.1) followed by the reaction of HjO, with iodide ions sensed by an iodide ISE [39], has not found practical use. 

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