Academic literature on the topic 'PVC membrane ISE'

The effect of PVC (Polyvinylchloride)-Based Membrane Composition to Ion Selective Electrode (ISE)-Hg(II) Performance using Ionophore DBA218C6 (N,N'-Dibenzyl-1,4,10,13-tetraoxa-7,16-diazacyclo octadecane), Plasticizer NPOE (Nitrophenyl Octhyl Ether), Anionic Site KTCPB (Potassium Tetrakis (4-chloro phenyl) borate) have been performed. Membrane compositions used were:(a) PVC (30 mg), NPOE (60 mg), DBA218C6(6 mg) and KTCPB (4 mg); (b) PVC(30 mg), NPOE (60 mg), DBA218C6(7 mg) and KTCPB (3 mg); (c) PVC (30 mg), NPOE (59 mg), DBA218C6 (8 mg) and KTCPB( 3 mg). The concentration range of interference ions Zn(II), Cd(II) and Pb(II) were 1.0 x 10-3 - 1.0 x 10-1 M. ISE-Hg(II) performance for membrane composition of 30 : 60 : 6 : 4 was 26.34 mV per decade (Nernstian Slope value) on Hg(II) concentration range of 1.0x10-6 - 1.0 x 10-1 M , membrane composition of 30 : 60 : 7 : 3 was 27.71 mV per decade on Hg(II) concentration range of 1.0 x10-6 - 1.0 x10-1 M, and membrane composition of 30 : 59 : 8 : 3 was 28.52 mV per decade on Hg(II) concentration range of 1.0 x10-6 - 1.0 x10-1 M with activity between pH 1.0-3.0. The concentration of interference ions : Zn(II), Cd(II) and Pb(II) in the range of 1.0 x 10-3 - 1.0 x 10-1 M with the ratio of the primary ion to interference ions of 4 : 1 gave real effect. As results, selectivities and sensitivities between ISE-Hg(II) and Ionophore DBA218C6 could be determined by PVC-Based Membrane Composition and the effect of Zn(II), Cd(II) and Pb(II) interference ions was observed in the concentration of 1,0 x10-3 - 1,0 x10-1 M. Keywords: membrane composition effect, ionophore DBA218C6, ISE-Hg(II)

Thirty years of ion-selective electrode (ISE) researches at the University of Wales, Cardiff are outlined. They summarize developments of PVC membrane ISEs, first for calcium and then of other systems, including the improved calcium dioctyl-phenyl-phosphate sensor for calcium and those of ion-exchangers, polyalkoxylates, and cyclic and acyclic polyethers for various anions and cations. Electrodes based on polyalkoxylates have interesting properties toward the polyethers themselves. Some ISE failure causes are discussed. Attention is given to applications, including analysis of wash liquors and nonionic surfactants, biomedical roles, and studies of sulfate-reducing bacteria activity. Coated-wire ISEs and ion-selective field effect transistors (ISFETs) are mentioned, as are other modes of ISE deployment. The review concludes with some fundamental features of PVC electrode membranes as determined by radiotracer, applied potential, and potentiostatic approaches.

The amide compound derived from humic acid has been applied as ionophore in ion selective electrode (ISE) measurement based on poly vinyl chloride (PVC) membrane. The carboxylic acid group of the humic acid was first modified to the corresponding amide and is expected to form complex with the target cation. This work aims at obtaining selectivity coefficient towards Ni2+ ion. The products of the reactions were observed using infra red (IR) spectrometer. The amide compound derived from humic acid was immobilized into the membrane with composition percentage (w/w) as the following 32% of PVC, 64% of plasticizer of either [orto-nitrophenil octyl ether (NPOE) or dioctylpthalate (DOP) or dibenzyl ether (DBE)], 2% of lipophilic anion [sodiumtetraphenylborate (NaTPB), and oleic acid], and 2% of ionophore the humic amide, respectively. The results show that ISE membrane give selective response to the Ni2+ ion at pH of 4,5 with response time of approximately 80 seconds. Among many others, the cations that give strong emf interference include Cu2+,Li+, K+, Pb2+, Na+, Zn2+, and Ca2+. The Nernstian factor of ISE membrane is close to +28 mV per decade with linear range of concentration of pNi2+ of 1-6, with composition PVC membrane, DBE as plasticizer, oleic acid as lipophilic anion, and humic amide as ionophore, respectively.

In this study, the new sulphite sensitive ion-selective electrode (ISE) was prepared. The ISE was prepared from a combination of 5% perfluorooctanesulfonic acid (PFOS), 40% PVC and 55% dibutylphthalate (DBF).The sensitivity of the ISE to 1.0x10- 7-1.0x10-1 M sulphite concentration was 58 and#177; 4 mV. Electrode sensitivity was characterized. The response time of this electrode is short and 30 s. The lifetime of ISE was approximately 210 days when used five times a day. It was determined that it can work at any pH value. It is not sensitive to anions and cations that may be present in the determination medium. The detection limit of the electrode against the sulfide concentration was measured as 1.2x10-8 M. The amount of sulfites in dried apricots in Turkey, was measured with electrodes. Sulfite amount in dried apricot was determined as 2.328 and#177; 0.2417 mg / kg according to the average of 5 experiments and 95% confidence interval. The same sample was measured with DPP as 2.521 and#177; 0.2785.The validation of the obtained results in each case was proved by statistical “t” and “F” tests.

In this study, the new sulphite sensitive ion-selective electrode (ISE) was prepared. The ISE was prepared from a combination of 5% perfluorooctanesulfonic acid (PFOS), 40% PVC and 55% dibutylphthalate (DBF).The sensitivity of the ISE to 1.0x10- 7-1.0x10-1 M sulphite concentration was 58 and#177; 4 mV. Electrode sensitivity was characterized. The response time of this electrode is short and 30 s. The lifetime of ISE was approximately 210 days when used five times a day. It was determined that it can work at any pH value. It is not sensitive to anions and cations that may be present in the determination medium. The detection limit of the electrode against the sulfide concentration was measured as 1.2x10-8 M. The amount of sulfites in dried apricots in Turkey, was measured with electrodes. Sulfite amount in dried apricot was determined as 2.328 and#177; 0.2417 mg / kg according to the average of 5 experiments and 95% confidence interval. The same sample was measured with DPP as 2.521 and#177; 0.2785.The validation of the obtained results in each case was proved by statistical “t” and “F” tests.

Research on the Ion-Selective Electrode (ISE) of coated wire-type tartrazine using chitosan as an ionophore has been developed. The variables used in the manufacture of ISE are membrane composition and immersion time. Meanwhile, the basic characteristics of ISE measured are Nernst value, measurement concentration range, detection limit, and measurement response time. The results showed that ISE tartrazine coated wire type had an optimum membrane composition in a mixture of chitosan: PVC: DOP of 3: 34: 63 (% w/w) and a membrane immersion time 20 minutes. The basic characteristics of ISE produce a Nernst value of 20.976 mV/decade. The measurement concentration range is 1×10-7-1×10-2 M with a detection limit of 2.749×10-7 M or 0.1469 ppm. The response time ranges from 10-60 seconds, with an average of 40 seconds.

In this work, we report the study of functionalized platinum (Pt) electrodes based on a polymeric membrane (PVC) including an ionophore (ethyln diamin tetracetic EDTA) sensitive for mercury ions Hg2+. The optimised working conditions of the sensors have been studied with regard to the sensitivity performances; in particular, the polarisation was adjusted to - 0.2V/SCE. Ion sensitivity of sensors have been tested for Hg(II) via Cd(II) in aqueous solution. A layer of EDTA deposited on platinum electrode has been characterised by impedance spectroscopy and cyclic voltammetry methods.

<p>The research on the highly selective and sensitive determination of Hg(II) ions using ion-selective electrodes (ISE) coated with the BEC4ND1 ionophore as a membrane has been successfully carried out. ISE was designed using the membrane composition of the [(BEC4ND1 ionophore : PTCPB : DOS : PVC) (3 : 2 : 60 : 35 % w/w)]. The ESI-BEC4ND1 ionophore has good characteristics where it shows a sensitivity value of 29.933 mV/decade in the Hg(II) ion concentration range of 10^-9 - 10^-1 M with a limit of detection (LoD) of 10^-7 M. The response time obtained is in the range of 4 - 8 minutes with a relative standard deviation (RSD) of 0.548. The ESI-BEC4ND1 ionophore also shows the average value of selectivity coefficient (K_ij) &lt; 1. These results indicate that the presence of Zn(II), Cd(II), and Pb(II) ions as interfering ions in the analyte solution does not affect the performance of the ESI-BEC4ND1 ionophore in detecting Hg(II) ions. The ESI-BEC4ND1 ionophore that has been developed shows good selectivity, sensitivity, stability, and reproducibility, so the ESI-BEC4ND1 ionophore is promising to be used as a Hg(II) ion detector in the environment.</p>

A novel single-piece all-solid-state ion-selective electrode (SC/ISE) based on carbon-screen printed is introduced. Polyaniline (PANI) is dissolved in a membrane cocktail that contains the same components used for making a conventional ion-selective polyvinyl chloride (PVC) matrix membrane. The membrane, having the PANI, is directly drop-casted on a carbon substrate (screen-printed-carbon electrode). PANI was added to act as an intermediary between the substrate and the membrane for the charge transfer process. Under non-equilibrium sensing mechanism, the sensors revealed high sensitivity towards 2,4-dichlorophenol (DCP) over the linearity range 0.47 to 13 µM and a detection limit 0.13 µm. The selectivity was measured by the modified separate solution method (MSSM) and showed good selectivity towards 2,4-DCP over the most commonly studied ions. All measurements were done in 30 mm Tris buffer solution at a pH 5.0. Using constant-current chronopotentiometry, the potential drift for the proposed electrodes was checked. Improvement in the potential stability of the SPE was observed after the addition of PANI in the sensing membrane as compared to the corresponding coated-wire electrode (membrane without PANI). The applicability of the sensor has been checked by measuring 2,4-DCP in different water samples and the results were compared with the standard HPLC method.

Screen-printed ion-selective electrodes were designed and characterized for the assessment of cyromazine (CYR) pesticide. A novel approach is to design tailor-made specific recognition sites in polymeric membranes using molecularly imprinted polymers for cyromazine (CR) determination (sensor I). Another sensor (sensor II) is the plasticized PVC membrane incorporating cyromazine/tetraphenyl borate ion association complex. The charge-transfer resistance and water layer reached its minimal by incorporating Polyaniline (PANI) solid-contact ISE. The designed electrodes demonstrated Nernstain response over a linear range 1.0 × 10−2–5.2 × 10−6 and 1.0 × 10−2–5.7 × 10−5 M with a detection limit 2.2 × 10−6 and 8.1 × 10−6 M for sensors I and II, respectively. The obtained slopes were 28.1 ± 2.1 (r2 = 0.9999) and 36.4 ± 1.6 (r2 = 0.9991) mV/decade, respectively. The results showed that the proposed electrodes have a fast and stable response, good reproducibility, and applicability for direct measurement of CYR content in commercial pesticide preparations and soil samples sprayed with CYR pesticide. The results obtained from the proposed method are fairly in accordance with those using the standard official method.

The monograph provides the basics of technology for the production of general construction and finishing works performed during the reconstruction of existing industrial and civil facilities: strengthening and restoration of exploited structures, as well as the construction of new buildings and structures designed at the reconstructed facility. The issues of conducting field surveys of operated buildings and structures in order to prepare a conclusion on the technical condition of load-bearing and enclosing structures are considered. The main design solutions and technology of work during the reconstruction (repair, reinforcement) of load-bearing and enclosing structures of operated facilities made of the following materials are given: monolithic and precast reinforced concrete; metal structures; brickwork; elements of wooden structures. The technology of rehabilitation (repair) of finishing coatings is given: monolithic plaster, wall and floor cladding with ceramic tiles and synthetic coatings, as well as repair of surfaces lined with slabs made of natural materials (granite, marble). The effective technology of construction of building structures of shallow foundations, double-layer insulated brick walls, buildings with a monolithic reinforced concrete supporting frame; the device of a waterproof carpet made of PVC membranes, etc. are described. For civil engineers. It can be useful for students, postgraduates and teachers of technical universities.

This research aimed to develop conceptually the pretensioned and stiffened membrane structures, using an experimental approach and computer simulation. The physical method of form finding included the pretensioned fabric with the glued grid made of the wooden sticks. Relaxation of the stressed membrane contributed to forming the specific anticlastic hyparic surface by energy release. The influence of the rigid elements pattern, intensity and direction of pretensioning on the final shape was investigated. The tensegrity structures were also built applying the same form finding way. These experiments led to the modelling of resulting samples with parametric design tools, namely Rhino and Grasshopper. Optimization of the final shape was carried out by changing parameters such as stiffenings configuration and membrane strength. This digital approach demonstrated successful simulation and rationalization of considered structures. Moreover, the final models can be used for further structural analysis and BIM. Considered membrane structures have very efficient load-bearing behavior. They are characterized by small weight, high light transmission and the ability to create large usable spaces free from columns. The most dangerous loads for membrane structures are wind and ponding. In practice, PTFE coated glass-fibre fabric and PVC coated polyester fabric are most suitable for pretensioned and stiffened membrane structures. The role of stiff elements can be played by steel profiles or metal tubes. The average time for the construction of a membrane structure is 6-15 months. Resulted pretensioned and stiffened membrane structures can be used as pavilions, roofs and awnings. They are distinguished by spectacular architectural view and very effective structural system. In addition, membrane tensile structures are characterized by high eco-efficiency and sustainability compared to other types of construction.

In order to be classified as a virus, certain criteria have to be fulfilled. Viruses must ● Be only capable of growth and multiplication within living cells, i.e. obligate intracellular parasite. Host cells could include humans, animals, insects, plants, protozoa, or even bacteria. ● Have a nucleic acid genome (either RNA or DNA, but not both) surrounded by a protein coat (capsid). ● Have no semipermeable membrane, though some have an envelope formed of phospholipids and proteins. ● Be inert outside of the host cell. Enveloped viruses are susceptible to inactivation by organic solvents such as alcohol. ● Perform replication by independent synthesis of components followed by assembly (c.f. binary fission in bacteria). Viruses are considered as a bundle of genetic programmes encoded in nucleic acids and packaged with a capsid +/ - envelope protein, which can be activated on entry into a host cell (compare this with computer viruses packaged in an enticing way in order to infect and take over control of your PC). Although they share some similarities in their properties, mycoplasma and chlamydia are true bacteria. The virion (assembled infectious particle) consists of viral nucleic acid and capsid. The nucleic acid of a virus can either be ribonucleic acid (RNA) or deoxyribonucleic acid (DNA), and the amount of genetic material varies widely, with some viruses able to encode a few proteins and others having genetic material that encodes hundreds of proteins. In association with the nucleic acid there may be non- structural viral proteins, such as a viral polymerase. The nucleic acid and non- structural proteins are protected by a surrounding layer of capsid proteins. The capsid includes proteins which can attach to host cell receptors. The proteins and the cell receptors to which they bind determine a virus’ tropism, i.e., the ability to bind to and enter different cell types. The term nucleocapsid refers to the nucleic acid core surrounded by capsid protein. Some viruses also have an envelope made up of phospholipids and proteins surrounding the nucleocapsid. This envelope can be formed by the host cell membrane during the process of a virus budding from a cell during replication.

The aim of this research project was to obtain information on the role of the cytochrome b559 in the function of Photosystem-II (PSII) with special emphasis on the light induced photo inactivation of PSII and turnover of the photochemical reaction center II protein subunit RCII-D1. The major goals of this project were: 1) Isolation and sequencing of the Chlamydomonas chloroplast psbE and psbF genes encoding the cytochrome b559 a and b subunits respectively; 2) Generation of site directed mutants and testing the effect of such mutation on the function of PSII under various light conditions; 3) To obtain further information on the mechanism of the light induced degradation and replacement of the PSII core proteins. This information shall serve as a basis for the understanding of the role of the cytochrome b559 in the process of photoinhibition and recovery of photosynthetic activity as well as during low light induced turnover of the D1 protein. Unlike in other organisms in which the psbE and psbF genes encoding the a and b subunits of cytochrome b559, are part of an operon which also includes the psbL and psbJ genes, in Chlamydomonas these genes are transcribed from different regions of the chloroplast chromosome. The charge distribution of the derived amino-acid sequences of psbE and psbF gene products differs from that of the corresponding genes in other organisms as far as the rule of "positive charge in" is concerned relative to the process of the polypeptide insertion in the thylakoid membrane. However, the sum of the charges of both subunits corresponds to the above rule possibly indicating co-insertion of both subunits in the process of cytochrome b559 assembly. A plasmid designed for the introduction of site-specific mutations into the psbF gene of C. reinhardtii. was constructed. The vector consists of a DNA fragment from the chromosome of C. reinhardtii which spans the region of the psbF gene, upstream of which the spectinomycin-resistance-conferring aadA cassette was inserted. This vector was successfully used to transform wild type C. reinhardtii cells. The spectinomycin resistant strain thus obtained can grow autotrophically and does not show significant changes as compared to the wild-type strain in PSII activity. The following mutations have been introduced in the psbF gene: H23M; H23Y; W19L and W19. The replacement of H23 involved in the heme binding to M and Y was meant to permit heme binding but eventually alter some or all of the electron transport properties of the mutated cytochrome. Tryptophane W19, a strictly conserved residue, is proximal to the heme and may interact with the tetrapyrole ring. Therefore its replacement may effect the heme properties. A change to tyrosine may have a lesser affect on the potential or electron transfer rate while a replacement of W19 by leucine is meant to introduce a more prominent disturbance in these parameters. Two of the mutants, FW19L and FH23M have segregated already and are homoplasmic. The rest are still grown under selection conditions until complete segregation will be obtained. All mutants contain assembled and functional PSII exhibiting an increased sensitivity of PSII to the light. Work is still in progress for the detailed characterization of the mutants PSII properties. A tobacco mutant, S6, obtained by Maliga and coworkers harboring the F26S mutation in the b subunit was made available to us and was characterized. Measurements of PSII charge separation and recombination, polypeptide content and electron flow indicates that this mutation indeed results in light sensitivity. Presently further work is in progress in the detailed characterization of the properties of all the above mutants. Information was obtained demonstrating that photoinactivation of PSII in vivo initiates a series of progressive changes in the properties of RCII which result in an irreversible modification of the RCII-D1 protein leading to its degradation and replacement. The cleavage process of the modified RCII-D1 protein is regulated by the occupancy of the QB site of RCII by plastoquinone. Newly synthesized D1 protein is not accumulated in a stable form unless integrated in reassembled RCII. Thus the degradation of the irreversibly modified RCII-D1 protein is essential for the recovery process. The light induced degradation of the RCII-D1 protein is rapid in mutants lacking the pD1 processing protease such as in the LF-1 mutant of the unicellular alga Scenedesmus obliquus. In this case the Mn binding site of PSII is abolished, the water oxidation process is inhibited and harmful cation radicals are formed following light induced electron flow in PSII. In such mutants photo-inactivation of PSII is rapid, it is not protected by ligands binding at the QB site and the degradation of the inactivated RCII-D1 occurs rapidly also in the dark. Furthermore the degraded D1 protein can be replaced in the dark in absence of light driven redox controlled reactions. The replacement of the RCII-D1 protein involves the de novo synthesis of the precursor protein, pD1, and its processing at the C-terminus end by an unknown processing protease. In the frame of this work, a gene previously isolated and sequenced by Dr. Pakrasi's group has been identified as encoding the RCII-pD1 C-terminus processing protease in the cyanobacterium Synechocystis sp. PCC 6803. The deduced sequence of the ctpA protein shows significant similarity to the bovine, human and insect interphotoreceptor retinoid-binding proteins. Results obtained using C. reinhardtii cells exposes to low light or series of single turnover light flashes have been also obtained indicating that the process of RCII-D1 protein turnover under non-photoinactivating conditions (low light) may be related to charge recombination in RCII due to back electron flow from the semiquinone QB- to the oxidised S2,3 states of the Mn cluster involved in the water oxidation process.