Sensors ion-selective electrodes

The potentiometry sensor (ion-selective electrode) controls application for determination of polymeric surface-active substances now gets the increasing value. Potentiometry sensor controls are actively used due to simple instmment registration, a wide range of determined concentrations, and opportunity of continuous substances contents definition. That less, the ionometry application for the cation polymeric SAS analysis in a solution is limited by complexity of polycation charge determination and ion-exchanger synthesis. 

Sensors (ion-selective electrodes) incorporating these receptors are typically based on lipophilic membranes made from highly plasticized... 

How analytical methods deal with interferences is one of the more ad hoc aspects of method validation. There is a variety of approaches to studying interference, from adding arbitrary amounts of a single interferent in the absence of the analyte to establish the response of the instrument to that species, to multivariate methods in which several interferents are added in a statistical protocol to reveal both main and interaction effects. The first question that needs to be answered is to what extent interferences are expected and how likely they are to affect the measurement. In testing blood for glucose by an enzyme electrode, other electroactive species that may be present are ascorbic acid (vitamin C), uric acid, and paracetamol (if this drug has been taken). However, electroactive metals (e.g., copper and silver) are unlikely to be present in blood in great quantities. Potentiometric membrane electrode sensors (ion selective electrodes), of which the pH electrode is the... 

Potentiometric sensors (ion-selective electrodes) These sensors are able to directly determine the activity of the ion of interest in the sample. In the following section, their behaviour is described in more detail. 

Any book must leave something out, and this one has left out a good deal it does not cover membranes used in packaging materials, sensors, ion-selective electrodes, fuel cells, battery separators, electrophoresis and thermal diffusion. In this final chapter, five processes that come under the general title of other are covered briefly. 

In a typical facilitated IT reaction an ion (most often, a cation, M+) is transferred from aqueous solution into the organic phase. A complex species formed by this ion and a ligand (L, initially present in organic phase) is easier to transfer than M+ itself. Reactions of this type are widely used in chemical sensors [ion-selective electrodes, liquid ion-exchangers (50)]. For SECM experiments, an aqueous solution of M+ is placed inside a micropipet, which serves as a tip electrode. The facilitated IT reaction at the micropipet tip is... 

Figure 2.6. Schematic representation of the construction of a crystal-sensor ion-selective electrode.

Owing to the popularity and vast modularity of the copper(l)-catalyzed azide-alkyne cycloaddition (CuAAC) [4,5], so-called click chemistry [24] (Fig. 1), many more 1,2,3-triazole-based anion receptors have been reported during the past 3 years (2008-2011). Reviews [25, 26] have been published to cover this new moiety in anion receptor chemistry. Therefore, this chapter will focus on triazole-based anion receptors that have not been reviewed to date. In addition, applications including sensors, ion-selective electrodes, catalysis, anion transport, and anion regulation, as well as their use in interlocked molecules, will be discussed. 

The ability of 1,2,3-triazole to bind anions with a C-H hydrogen bond is covered in Chap. 3, Binding Anions in Rigid and Reconfigurable Triazole Receptors by Lee and Hood. Applications including sensors, ion-selective electrodes, catalysis, anion transport and anion regulation, as well as their use in interlocked molecules, are discussed. 

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. 

Sources of Error. pH electrodes are subject to fewer iaterfereaces and other types of error than most potentiometric ionic-activity sensors, ie, ion-selective electrodes (see Electro analytical techniques). However, pH electrodes must be used with an awareness of their particular response characteristics, as weU as the potential sources of error that may affect other components of the measurement system, especially the reference electrode. Several common causes of measurement problems are electrode iaterferences and/or fouling of the pH sensor, sample matrix effects, reference electrode iastabiHty, and improper caHbration of the measurement system (12). 

The majoiity of the various analyte measurements made in automated clinical chemistry analyzers involve optical techniques such as absorbance, reflectance, luminescence, and turbidimetric and nephelometric detection means. Some of these ate illustrated in Figure 3. The measurement of electrolytes such as sodium and potassium have generally been accomphshed by flame photometry or ion-selective electrode sensors (qv). However, the development of chromogenic ionophores permits these measurements to be done by absorbance photometry also. 

Ion-selective electrodes can also become sensors (qv) for gases such as carbon dioxide (qv), ammonia (qv), and hydrogen sulfide by isolating the gas in buffered solutions protected from the sample atmosphere by gas-permeable membranes. Typically, pH glass electrodes are used, but electrodes selective to carbonate or sulfide may be more selective. 

Kimura and coworkers [17], Diamond [18], and Damien et al. [19] have described that the polymeric calix-[4]arenes have been used as ionophores in ion selective electrodes for Na (based on calixarene esters and amides) and for Na and Cs (based on p-alkylcalixarene acetates). The electrodes are stated to function as poten-tiometric sensors as well, having good selectivity for primary ion, virtually no response to divalent cations, and being stable over a wide pH range. 

The sensor is an ammonium ion-selective electrode surrounded by a gel impregnated with the enzyme mease (Figme 6-11) (22). The generated ammonium ions are detected after 30-60 s to reach a steady-state potential. Alternately, the changes in the proton concentration can be probed with glass pH or other pH-sensitive electrodes. As expected for potentiometric probes, the potential is a linear function of the logarithm of the urea concentration in the sample solution. 

Legin AV, Vlasov YG, Rudnitskaya AM, Bychkov EA (1996) Cross-sensitivity of chalcogenide glass sensors in solutions of heavy metal ions. Sens Actuators B 34 456 61 De Marco R, Shackleton J (1999) Cahbration of the Hg chalcogenide glass membrane ion-selective electrode in seawater media. Talanta 49 385-391... 

Y. Yamamoto. Studies on Amperometric Ion-Selective Electrode Sensors. PhD Thesis, Kyoto University, Kyoto 1991. 

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