Neutralizer, membrane based

To evaluate the contribution of the SHG active oriented cation complexes to the ISE potential, the SHG responses were analyzed on the basis of a space-charge model [30,31]. This model, which was proposed to explain the permselectivity behavior of electrically neutral ionophore-based liquid membranes, assumes that a space charge region exists at the membrane boundary the primary function of lipophilic ionophores is to solubilize cations in the boundary region of the membrane, whereas hydrophilic counteranions are excluded from the membrane phase. Theoretical treatments of this model reported so far were essentially based on the assumption of a double-diffuse layer at the organic-aqueous solution interface and used a description of the diffuse double layer based on the classical Gouy-Chapman theory [31,34]. 

Simple encapsulation or dispersion of neutral carriers in silicone rubber is an easy way to fabricate silicone-rubber ion-sensing membranes based on neutral carriers. 

W., Lifetime of neutral-carrier-based liquid membranes in aqueous samples and blood and the lipophilicity of membrane components, Anal. Chem. 1991 63 596-603. 

Seiler K., Wang K., Bakker E., Morf W.E., Rusterholz B., Spichiger U.E., Simon W., Characterization of sodium-selective optode membranes based on neutral ionophores and assay of sodium in plasma, Clinical Chemistry 1991 37 1350-1355. 

R. Eugster, P.M. Gehrig, W.E. Morf, U.E. Spichiger, and W. Simon, Selectivity-modifying influence of anionic sites in neutral-carrier-based membrane electrodes. Anal. Chem. 63, 2285-2289 (1991). 

E. Bakker and E. Pretsch, Lipophilicity of tetraphenylborate derivatives as anionic sites in neutral carrier-based solvent polymeric membranes and lifetime of corresponding ion-selective electrochemical and optical sensors. Anal. Chim. Acta 309, 7-17 (1995). 

W.E. Morf, K. Seiler, B. Rusterholz and W. Simon, Design of a calcium-selective optode membrane based on neutral ionophores, Anal. Chem., 62 (1990) 738-742. 

They are classified by membrane material into glass membrane electrodes, crystalline (or solid-state) membrane electrodes, and liquid membrane electrodes. Liquid membrane electrodes are further classified into liquid ion-exchange membrane electrodes and neutral carrier-based liquid membrane electrodes. Some examples are shown in Fig. 5.36 and Table 5.3. If the membrane is sensitive to ion i of charge Z and the activities of i in the sample and internal solutions are equal to (i) and a2(i), respectively, the membrane potential, m, which is developed across the membrane, is... 

The most widely used sensor for chloride ions in clinical analyzers is based on an ion-exchanger, a quaternary alkylammonium chloride, dispersed in a plastic membrane. It is not an ideal sensor due to the interference of lipophilic anions (e.g., salicylates, bromides) and lip-ophylic cations (e.g., bacteriostatic agents, anesthetics) and a relatively poor selectivity towards hydrogen carbonates (bicarbonates). However, compared to charged anion- and neutral carrier-based membranes that have been tested, it is still the best-suited for automated analyzers. 

The electrocatalytic oxygen reduction in DMFC systems requires the development of highly selective electrodes in the presence of methanol. Present electrolyte membranes based on Nafion 117 are permeable to methanol (crossover effect), which depolarizes the platinum cathode [81,82]. For this reason, our strategy, some years ago, was to produce electrocatalytic materials from the thermal decomposition of some neutral transition-metal carbonyl compounds in the presence... 

Lee HJ, Yoon IJ, Yoo CL, Pyun HJ, Cha GS, Nam H. Potentiometric evaluation of solvent polymeric carbonate-selective membranes based on molecular tweezer-type neutral carriers. Anal Chem 2000 72 4694-9. 

Eugster R, Spichiger UE, Simon W, Membrane model for neutral-camer-based membrane electrodes containing ionic sites. Anal. Chem. 1993 65, 689-695. 

Ionized calcium and total calcium measurements are both performed with PVC-type electrodes. Membranes based on lipophilic alkyl phosphates with phosphonate plasticizers have only marginal selectivity over magnesium but have been used in the past to determine ionized calcium (i.e., free calcium) in undiluted blood samples (M8). Interference from protons at low pHs prevents such membranes from being employed for total calcium determinations on samples diluted with acid. Use of ionophore ETH 1001 (see Fig. 2) overcomes any concerns about selectivity, whether from magnesium or pH, and is now the neutral carrier system most often utilized within analyzers to detect ionized or total calcium. 

Liquid membrane electrodes (1) classical ion-exchangers (with mobile positively and negatively charged sites as hydrophobic cations or hydrophobic anions), for example K+, Cl selective electrodes, (2) liquid ion-exchanger based electrodes (with positively or negatively charged carriers, ionophores), for example Ca2+, NOJ selective electrodes, (3) neutral ionophore based liquid membrane electrodes (with electrically neutral carriers, ionophores), for example Na+, K+, NI I), Ca2+, Cl selective electrodes. 

Liquid membrane electrodes are three (or four) component membrane based devices with positively charged, negatively charged, or electrically neutral ionophores. The main component of the liquid membrane is the ionophore, or mobile carrier—a compound with binding properties to different ions and responsible for the ion selectivity. The carriers are incorporated into membrane matrices, most commonly into plasticized poly(vinyl chloride). Liquid membranes often contain lipophilic salt additives also to enhance the permselectivity of hte membrane. 

The major problem in developing neutral carrier-based membrane solution (cocktail) is to produce ion-selective microelectrodes of relatively low resistance. In order to keep the microelectrode resistance low, the membrane... 

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