PVC membranes

PVC) membrane, eliminating the need for a reservoir containing di-(n-decyl) phosphate. 

The properties of several representative liquid-based ion-selective electrodes are presented in Table 11.3. An electrode using a liquid reservoir can be stored in a dilute solution of analyte and needs no additional conditioning before use. The lifetime of an electrode with a PVC membrane, however, is proportional to its exposure to aqueous solutions. For this reason these electrodes are best stored by covering the membrane with a cap containing a small amount of wetted gauze to... 

Creager and colleagues designed a salicylate ion-selective electrode using a PVC membrane impregnated with tetraalkylammonium salicylate. To determine the ion-selective electrode s selectivity coefficient for benzoate,... 

This experiment describes the preparation of a flow-through potentiometric electrode assembly incorporating a valinomycin-PVC membrane in the transport tubing. The... 

The greater portion of PVC is installed in the mechanically fastened roofing system a lesser portion is installed in fully adhered appHcations. Although PVC was once heavily used in ballasted roofing systems, there are only a small number installed in the 1990s. Fleece-back membrane is popular in the PVC constmction for both fully adhered appHcations as well as in appHcations where a separator sheet is needed. PVCs ate resistant to vafious weather conditions, bactefial growth, and industfial chemicals. These membranes ate chemically incompatible with bituminous materials. PVCs ate offered in a variety of colors. The physical characteristics of a PVC membrane have been described (15). 

Caleadered PVC has approximately 55% of the PVC/PVC alloy segmeat, PVC dispersioa coatiags usiag a reinforcement are 40%, and PVC extmsion with width limitations is about 5%. Almost all PVC membranes are reiaforced or supported with thicknesses from 1.2—2.4 mm (47—96) mils. Converters typically purchase roUstock ia 5—6 ft widths (1.5—1.8 m). Colors and designs are not common most manufacturers offer a soHd white, gray, or tan sheet. 

Fig. 10. Response of an ammonium ion-selective electrode which was made from nonactin dissolved in a PVC membrane mounted in a Phillips electrode body (ISE-561, Glasblaserie Mitller, Zurich) referenced against an SCE to a spHt-stream EIA system, (a) EIA response to injected standards containing both glutamine and ammonium chloride lines A—E contain both glutamine and ammonium chloride E—G contain only glutamine, (b) Strip-chart...

FIGURE 5-11 The recognition process occurring at the TDMAC/PVC membrane/sample interface used for measurements of heparin. (Reproduced with permission from reference 26.)... 

Fig. 7. Schematic diagram of digoxin antibody sensing electrode (a) PVC membrane containing digoxin-carrier conjugate (b) inner filling solution, 0.01 M KCI (c) plasticizer, dibutyl sebacate (d) digoxin antibodies. (From 152, with permission)...

Applicability in biological ion assay is an important factor for biocompatible potentio-metric ion sensors. Attempts were made to determine Na" " concentrations in human blood sera by using silicone-rubber membrane Na+-ISFETs based on (5) [Fig. 17(a)] [29]. The found values for Na concentration in undiluted, 10-fold diluted, and 100-fold diluted serum samples are in good agreement with the Na" " calibration plots. Even in the undiluted serum samples, only a slight potential shift was observed from the calibration. This indicates that the calixarene-based silicone-rubber-membrane Na+-ISFETs are reliable on serum Na assay. For comparison with the silicone-rubber membrane, Na -ISFETs with corresponding plasticized-PVC membrane containing (2) or (5) were also tested for the Na assay. The found values of Na" " concentration... 

The design of bioeompatible (blood compatible) potentiometric ion sensors was described in this chapter. Sensing membranes fabricated by crosslinked poly(dimethylsiloxane) (silicone rubber) and sol gel-derived materials are excellent for potentiometric ion sensors. Their sensor membrane properties are comparable to conventional plasticized-PVC membranes, and their thrombogenic properties are superior to the PVC-based membranes. Specifically, membranes modified chemically by neutral carriers and anion excluders are very promising, because the toxicity is alleviated drastically. The sensor properties are still excellent in spite of the chemical bonding of neutral carriers on membranes. 

PVC membranes have been used as a subslab membrane during radon mitigation work in existing houses. They are usually sealed with solvents and were developed as roofing membranes. 

Sun et al. [13] developed a selective electrode for the determination of OTC hydrochloride. The electrode is constructed of a plasticized PVC membrane... 

The selective determination of Cu(II) was accomplished by making use of pyrocatechol violet indicator, dissolved in plasticized PVC membrane as a... 

Among all the polymers used in preparing ion-selective membranes, poly(vinylchloride) (PVC) is the most widely used matrix due to its simplicity of membrane preparation [32, 70], In order to ensure the mobility of the trapped ionophore, a large amount of plasticizer (approximately 66%) is used to modify the PVC membrane matrix (approximately 33%). Such a membrane is quite similar to the liquid phase, because diffusion coefficients for dissolved low molecular weight ionophores are high, on the order of 10 7-10 8cm2/s [59],... 

Polymer-based pH sensors are not suitable for continuous in-vivo measurements due to the poor biocompatibility of plasticizers used in the polymer membrane. To minimize such a problem, surface treatment or using a reduced amount of plasticizers has been proposed [71]. In order to improve stability and adhesion, polyurethane has been used as an alternative to PVC membranes in the construction of pH sensing membranes [72, 73],... 

J.E. Zachara, R. Toczylowska, R. Pokrop, M. Zagorska, A. Dybko, and W. Wroblewski, Miniaturised all-solid-state potentiometric ion sensors based on PVC-membranes containing conducting polymers. Sens. Actuators B. 101, 207-212 (2004). 

Another aspect of tin as a constituent of electrode material is shown by tin(IV)TPP complexes incorporated into PVC membrane electrodes. These increase the selectivity to salicylate over anions such as Cl-, Br- I-, I()4, Cl()4, citrate, lactate and acetate. The specificity is attributed to the oxophilic character of the Sn ion in TPP at the axial coordination sites. Indeed, carboxyl groups incorporated into the membrane polymer compete for these binding sites. The complete complex structure is important. Substitution of TPP with octaethylporphirine results in loss of salicylate selectivity231. Preparation and analytical evaluation of a lead-selective membrane electrode, containing lead diethyldithiocarbamate chelate, has also been described232. 

Figure 3. Components of an ion-selective electrode chemical sensor (left) and photographs of electrode body (right) showing electrode barrel with silver-silver chloride electrode, and screw-on electrode tip with end-clip for attaching the PVC membrane containing immobilised molecular receptors that will selectively bind specific target species.

The fourth type of mediator-based cation optical sensing is using potential sensitive dye and a cation selective ionophore doped in polymer membrane. Strong fluorophores, e.g. Rhodamine-B C-18 ester exhibits differences in fluorescence intensity because of the concentration redistribution in membranes. PVC membranes doped with a potassium ionophore, can selectively extract potassium into the membrane, and therefore produce a potential at the membrane/solu-tion interface. This potential will cause the fluorescent dye to redistribute within the membrane and therefore changes its fluorescence intensity. Here, the ionophore and the fluorescence have no interaction, therefore it can be applied to develop other cation sensors with a selective neutral ionophore. 

Although not strictly relevant to amperometric sensor technology, various metalloporphyrins [Co(III), Mn(III), Fe(III) Fig. 45] have been shown to sense anions potentiometrically with selectivity sequences dependent on the centrally bound metal (Amman et al., 1986 De et al., 1994). For example the anti-Hofmeister selectivity sequence SCN" > I" > CIO4 > N02 > Br > Cl- > NOJ was exhibited by PVC membrane electrodes containing [87]. 

The sensor reported by Shirai(69) used a natural carboxylic polyether antibiotic (Aem = 481 nm) for the detection of magnesium and calcium. Detection limits of I0 5 and KT4 M, respectively, were reported but, interference from other metals was difficult to overcome. Ishibashi(69) used a bulkier hexadecyl-acridine orange dye (Xem = 525 nm) plasticized in a PVC membrane for the fluorescent detection of ammonium ions. Signal interference due to superfluous ions and poor detection limits of KT5 M restricted the use of the probe. 

The function of an immuno-electrode [28] containing a model antibody (Concanavalin A) fixed in a polymeric film on a platinum electrode is probably based on other effects than those utilized in ISEs. Immuno-electrodes suitable for direct determination of antibodies were prepared by fixing a conjugate of an ionophore and an immunogen (for example the compound of dibenzo-18-crown-6 with dinitrophenol) in a PVC membrane. This system responded to the antibody against dinitrophenol [52, 53]. 

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