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Chemical ionophores

Chemical modification of monensin, polyether ionophoric antibiotic with bound tetrahydropyran, two tetrahydrofuran, and octahydrospiro-2,2 -furopyran fragments 97YZ583. [Pg.229]

Design and synthesis of crown ethers and other macroheterocycles as highly selective ionophores for chemical ion sensors 98YGK291. [Pg.269]

It was found in later work that it is precisely the idea of ionic hydration that is able to explain the physical nature of electrolytic dissociation. The energy of interaction between the solvent molecules and the ions that are formed is high enough to break up the lattices of ionophors or the chemical bonds in ionogens (for more details, see Section 7.2). The significance of ionic hydration for the dissociation of electrolytes had first been pointed out by Ivan A. Kablukov in 1891. [Pg.105]

The rate of the ion transfer is governed by the complexation reaction, whose rate constant should not depend on potential since it is a purely chemical reaction. However, the concentrations of the reactant change with potential. Typically, the ionophore is uncharged, so that a change in the potential drop affects only the concentration of the ions at the interface. If the thickness X of the interface is neglected, the concentration of the ion at the interface is given by ... [Pg.181]

Various types of research are carried out on ITIESs nowadays. These studies are modeled on electrochemical techniques, theories, and systems. Studies of ion transfer across ITIESs are especially interesting and important because these are the only studies on ITIESs. Many complex ion transfers assisted by some chemical reactions have been studied, to say nothing of single ion transfers. In the world of nature, many types of ion transfer play important roles such as selective ion transfer through biological membranes. Therefore, there are quite a few studies that get ideas from those systems, while many interests from analytical applications motivate those too. Since the ion transfer at an ITIES is closely related with the fields of solvent extraction and ion-selective electrodes, these studies mainly deal with facilitated ion transfer by various kinds of ionophores. Since crown ethers as ionophores show interesting selectivity, a lot of derivatives are synthesized and their selectivities are evaluated in solvent extraction, ion-selective systems, etc. Of course electrochemical studies on ITIESs are also suitable for the systems of ion transfer facilitated by crown ethers and have thrown new light on the mechanisms of selectivity exhibited by crown ethers. [Pg.629]

Solvent polymeric membranes, conventionally prepared from a polymer that is highly plasticized with lipophilic organic esters or ethers, are the scope of the present chapter. Such membranes commonly contain various constituents such as an ionophore (or ion carrier), a highly selective complexing agent, and ionic additives (ion exchangers and lipophilic salts). The variety and chemical versatility of the available membrane components allow one to tune the membrane properties, ensuring the desired analytical characteristics. [Pg.101]

Ion-selective electrode research for biomedical analysis is no longer the relatively narrow, focused field of identifying and synthesizing ionophores for improved selectivity and the integration of ion-selective electrodes into clinical analyzers and portable instruments. These efforts have matured now to such an extent that they can teach valuable lessons to other chemical sensing fields that are just emerging technologies. [Pg.131]

Fig. 18a.8. Chemical structures of some commonly known cation ionophores used in the design of ion-selective electrodes. Fig. 18a.8. Chemical structures of some commonly known cation ionophores used in the design of ion-selective electrodes.
Gad, S.C., Reilly, C., Siino, K.M. and Gavigan, F.A. (1985). Thirteen cationic ionophores Neurobehavioral and membrane effects. Drug Chemical Toxicol. 8 (6)451-468. [Pg.966]

FSIS laboratories also use chemical techniques and instrumentation to identify select antibiotic residues. The tetracyclines of interest are identified by thin layer chromatography. Sulfonamides are detected and quantified by fluorescence thin lay chromatography and confirmed by gas chromatography/mass spectrometry. Amoxicillin and gentamycin are identified and/or quantified by high pressure liquid chromatography. Similar techniques are used to identify ionophores and other antimicrobials of interest. [Pg.141]

Figure 5.23 — Flow-through ionophore-based sensor for the determination of lithium in serum. (A) Mechanism involved in the sensor response (symbol meanings as in Fig. 5.20). (B) Diffuse reflectance flow-cell (a) upper stainless steel cell body (A) silicon rubber packing (c) quartz glass window (d) Teflon spacer (0.05 mm thickness) (e) hydrophobic surface mirror (/) lower stainless steel cell body. For details, see text. (Reproduced from [90] with permission of the American Chemical Society). Figure 5.23 — Flow-through ionophore-based sensor for the determination of lithium in serum. (A) Mechanism involved in the sensor response (symbol meanings as in Fig. 5.20). (B) Diffuse reflectance flow-cell (a) upper stainless steel cell body (A) silicon rubber packing (c) quartz glass window (d) Teflon spacer (0.05 mm thickness) (e) hydrophobic surface mirror (/) lower stainless steel cell body. For details, see text. (Reproduced from [90] with permission of the American Chemical Society).
Another chemical class of sedative-hypnotic drugs, the barbiturates, also binds to receptors associated with the GABA-chloride ionophore, but these drugs appear to prolong rather than intensify GABA s effects. Fig. 24.4 shows the presumed drug receptor-GABA-chloride ionophore relationship. [Pg.357]

Figure 22. (a) Square root of the SHG intensity (V/(2w)) and (b) observed membrane potential as a function of the concentration of K ion in the adjacent aqueous solution containing KCI (o) and KSCN ( ), respectively. The composition of the PVC matrix liquid membrane containing ionophore 80 is the same as in Figure 21 b (reprinted with permission from Ana/. Chem. 1995, 67, 574. Copyright 1995 American Chemical Society). [Pg.254]

Glasses exist that fnnction as selective electrodes for many different monovalent and some divalent cations. Alternatively, a hydrophobic membrane can be made semiper-meable if a hydrophobic molecnle called an ionophore that selectively binds an ion is dissolved in it. The selectivity of the membrane is determined by the structnre of the ionophore. Some ionophores are natnral products, such as gramicidin, which is highly specific for K+, whereas others such as crown ethers and cryptands are synthetic. Ions such as, 1, Br, and N03 can be detected using quaternary ammonium cationic surfactants as a lipid-soluble counterion. ISEs are generally sensitive in the 10 to 10 M range, but are not perfectly selective. The most typical membrane material used in ISEs is polyvinyl chloride plasticized with dialkylsebacate or other hydrophobic chemicals. [Pg.598]


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See also in sourсe #XX -- [ Pg.162 ]




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