Membranes ion-selective electrodes

Electrochemical cell for potentiometry with an ion-selective membrane electrode. 

Radio, N. Komijenovic, J. Potentiometric Determination of an Overall formation Gonstant Using an Ion-Selective Membrane Electrode, /. Chem. Educ. 1993, 70, 509-511. 

Information retrieval, 10 (1974) 1 Inotropic steroids, design of, 30 (1993) 135 Insulin, obesity and, 17 (1980) 105 Ion-selective membrane electrodes,... 

T. Sokalski, T. Zwickl, E. Bakker, and E. Pretsch, Lowering the detection limit of solvent polymeric ion-selective membrane electrodes. 1. Steady-state ion flux considerations. Anal. Chem. 71,1204—1209 (1999). 

Figure 4.16 — Schematic diagram of a split-stream FI system used for the determination of glutamine in bioreactor media C de-ionized water carrier stream R buffer diluent reagent stream S sample injection point L delay coils CPG controlled pore glass enzyme reactor ISE ammonium ion-selective membrane electrode W waste. (Reproduced from [139] with permission of the American Chemical Society).

A series of ion-selective membrane electrodes based on neutral carrier solvent polymeric membranes has been designed for the potentiometric determination of ion activities (for reviews see Refs. 52, 65). Systems with analytically relevant selectivities for Li+, Na+, K+, NHJ, Ca2+, and Ba2+, are available. In agreement with the treatment given in Sections III and IV, the ions preferred in potentiometric studies may be transported preferentially through the same membranes in electrodialytic experiments. So far, selective carrier transports have been realized for Li+, Na+, K+, and Ca2+. 

Open-circuit potential (OCP) — This is the - potential of the - working electrode relative to the - reference electrode when no potential or - current is being applied to the - cell [i]. In case of a reversible electrode system (- reversibility) the OCP is also referred to as the - equilibrium potential. Otherwise it is called the - rest potential, or the - corrosion potential, depending on the studied system. The OCP is measured using high-input - impedance voltmeters, or potentiometers, as in - potentiometry. OCP s of - electrodes of the first, the second, and the third kind, of - redox electrodes and of - ion-selective membrane electrodes are defined by the - Nernst equation. The - corrosion po-... 

P13. Pungor, E., and Toth, K., Ion-selective membrane electrodes. Analyst (London) 95, 625-648 (1970). 

Thus, ion-selective membrane electrodes can be defined as electrochemical sensors that allow potentiometric measurements of the activity of particular species in aqueous and mixed solvents or partial pressures of dissolved gases in water. However, these sensors may respond to certain other ions in the sample in addition to the selected i ion interferences by such j ions are usually expressed by the Nikolskii-Eisenman Eq. (17) ... 

Baiulescu, G.E. Cosofret, V.V. Applications of Ion-Selective Membrane Electrodes in Organic Analysis Horwood Chichester, 1977. 

Stefan, R.-I. Baiulescu, G.-E. Aboul-Enein, H.Y. Ion-selective membrane electrodes in pharmaceutical analysis. Crit. Rev. Anal. Chem. 1997, 27, 307-321. 

Validation criteria for developing ion-selective membrane electrodes for analysis of pharmaceuticals... 

Abstract The problem of validation criteria for developing ion-selective membrane electrodes for the analysis of pharmaceuticals arises from the connection between the reliability of ion-selective membrane electrodes construction and the reliability of the analytical information. Liquid membrane selective electrodes are more suitable for validation than the solid variety. The influence of the stability of... 

Key words Ion-selective membrane electrodes Reliability of construction Reliability of analytical information Validation criteria Analysis of pharmaceuticals... 

For pharmaceutical analyses, it is necessary to have reliable methods. Results obtained using ion-selective membrane electrodes are the best because of the simplicity, rapidity, and accuracy of direct and continuous measurement of the activity of the ions in the solution. Another very important reason for the selection of electrochemical sensors for pharmaceutical assay is non-interference of by-products when the purity of a raw material is to be determined. 

The validation criteria for ion-selective membrane electrodes (ISMEs) can be established only by taking into account their reliability and its effect on the reliability of the analytical information that it is obtained. 

The good relationship between the reliability of developed ion-selective membrane electrodes and the reliability of obtained analytical information assures the validation of the ISMEs for analysis. 

The validation of ion-selective membrane electrodes is based on the reproducibility of their development, the simplicity and rapidity of their construction, and their response characteristics. Typically, these response characteristics include minimum 50 mV/decade for the slope, 10 6 mol/L for limit of detection, large working range, and low response time, which can be assured only by the best counter ion and matrix (PVC and plasticizer for solid membrane electrodes and solvent for liquid membrane electrodes). 

Figure 4-1 Schematic of ion-selective membrane electrode-based potent ometric ceil.

Oesch U, Ammann D, Simon W. Ion-selective membrane electrodes for clinical use. CUn Chem 1986 32 1448-59. 

Scott WJ, Chapoteau E, Kumar A, Ion-selective membrane electrode for rapid automated determinations of total carbon dioxide. Clin Chem 1986 312 137-41. 

Potentiometric methods of analysis are based on measuring the potential of electrochemical cells without drawing appreciable current. For nearly a century, potentiometric techn iques have been used to locate end points in titrations. In more recent methods, ion concentrations are measured directly from the potential of ion-selective membrane electrodes. These electrodes are relatively free from interferences and provide a rapid, convenient, and nondestructive means of quantitatively determining numerous important anions and cations. ... 

The various chapters in this book address the topics of material selection, characterization and evaluation as well as membrane preparation, characterization and evaluation. At the expense of neglecting membranes for applications such as controlled release and impermeable barriers, this book focuses on synthetic membranes for separation processes as well as active membranes and conductive membranes. While many of the concepts developed herein can be extrapolated to other applications, the Interested reader is referred elsewhere for specific details (for example, controlled release (25-30), coating and packaging barriers (31-33), contact lenses (34,35), devolatilization (36), ion-selective membrane electrodes (37-42) and membranes in electrochemical power sources (43)). 

H5. Hopirtean, E., and Kormos, F., Ion-selective membrane electrodes for organic analysis—codeine selective liquid membrane electrode. Chem. Anal. (Warsaw) 25, 209-213 (1980). 

R2. Rechnitz, G. A., Nogle, G. J., Bellinger, M. R., and Lees, H., Determination of total carbon dioxide in serum and plasma using a carbonate ion-selective membrane electrode. Clin. Chim. Acta 76, 295-307 (1977). 

Histamine has been determined with an ion selective membrane electrode based on p-fluorophenyl borate (Katsu et al., 1986). 

Ion-selective membrane electrodes as amperometric and potentiometric biosensors cannot be successfully used for ion monitoring in water. Their main characteristic is detection of an ion in the sample continuously and without any prior separation. The sampling process for a solid sample is reduced at its dissolution in distilled water. Due to the complexity of the matrix for wastewater or for seawater samples, there are a number of interfering inorganic and organic ions. Using biosensors for water analysis, one can obtain the total quantity of organic substances that are contained in a class it is practically impossible to discriminate the content of every compound from within the same class. 

Because of the complexity of the matrix, air, water, and soil samples require a very ardous sampling process, whose most important step is separation. The strong connection between the reliability of the sampling process and the reliability of the analytical process requires a reliable sampling process that obtains optimum reliability for the analytical information as long as the analytical method chosen is the best for the components that must be assayed. Thus, the reliability is also connected with the analytical method used for components assay. For air, water, and soil samples, the best reliability of the analytical information is obtained using spectrometric methods. The electrometric techniques, especially the ion-selective membrane electrodes or biosensors, cannot be used for determination of components in environmental samples with good results because of the low selectivity of the methods. 

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