Solution pH Conditions Research Articles

Detection of cytochrome c using a conducting polymer mediator containing electrode

AbstractIn this work, we have demonstrated the feasibility of cytochrome c detection using a novel mediator‐incorporated conducting polypyrrole‐based electrode. The mediator used was Fe(CN). The effect of buffer solution pH and electrochemical conditions on the voltammetric responses of cytochrome c have been investigated. The analytical utility of this electrode has been demonstrated using flow injection analysis.

Electrospray mass spectrometric investigation of the chaperone SecB.

Electrospray ionization mass spectrometry was used to investigate the structure of the Escherichia coli chaperone protein SecB. It was determined that the N-terminal methionine of SecB has been removed and that more than half of all SecB monomers are additionally modified, most likely by acetylation of the N-terminus or a lysine. The use of gentle mass spectrometer interface conditions showed that the predominant, oligomeric form of SecB is a tetramer that is stable over a range of solution pH conditions and mass spectrometer interface heating (i.e., inlet capillary temperatures). At very high pH, SecB dimers are observed. SecB contains a region that is hypersensitive to cleavage by proteinase K and is thought to be involved in conformational changes that are crucial to the function of SecB. We identified the primary site of cleavage to be between Leu 141 and Gln 142. Fourteen amino acids are removed, but the truncated form remains a tetramer with stability similar to that of the intact form.

Influence of processing conditions on the release of sodium fluoride from oligomeric l-lactic acid matrices

Matrices were prepared in the shape of rods with a diameter of 4 mm and a length of 10 mm. They were composed of oligomers of l-lactic acid ( M w 2550–11730 Daltons) and micronized sodium fluoride particles. Sodium fluoride concentration was kept in the range 5–60%. Matrices were prepared by melting the mixture of l-lactic acid oligomer and sodium fluoride. Two types of products according to the applied cooling rate were prepared and evaluated for release characteristics in vitro. Sink conditions of isotonic phosphate buffer solution pH = 7.4 at 37 °C were maintained throughout the experiment. The concentration of dissolved sodium fluoride was determined by ion-selective electrode. It was documented that the release rate of sodium fluoride is strongly dependent on the molecular weight of oligomer. The effects of sodium fluoride concentration and cooling rate of melted mixture were evaluated by ANOVA, separately for each oligomer. The effect of sodium fluoride concentration was significant at each oligomer studied, while the influence of cooling rate was significant with higher molecular weight oligomers. Moreover, this effect is ambiguous and dependent on the capability of oligomers to form crystalline phases and on the form and geometric arrangement of this phase.

Photodecomposition of 2,4-dichlorophenol in aqueous solution catalyzed by cadmium sulfide particles

In this paper the degradation of 2,4-dichlorophenol in the presence of cadmium sulfide suspensions by ultraviolet illumination is studied under various solution pH conditions, reaction times, and CdS loadings. The increase in the 2,4-dichlorophenol removal at alkaline condition by photocatalysis is possibly attributed to the distribution of protonated and deprotonated species at different solution pH conditions. The degradation and demineralization of 2,4-dichlorophenol by the photocatalytic process can be described fairly well by a simplified two step consecutive reaction scheme based on carbon balance.

Aqueous alteration on the hydrous asteroids: Results of EQ3/6 computer simulations

In order to understand the course of aqueous alteration of the hydrous asteroids we constructed two models for carbonaceous chondrite precursor material, one (model A) based upon the anhydrous mineralogy of the abundant CM chondrites and the other (model B) based upon that of the equally abundant CV chondrites. We then proceeded to calculate the likely course of aqueous alteration on asteroids composed of these materials through the use of the EQ3/6 computer algorithm. We find that the alteration mineralogy of the CM chondrites (and by extension the CM parent asteroids) may best be produced by starting with the anhydrous mineralogy of the same CM chondrites, at temperatures of 1 to approximately 25°C, and at total solution carbon concentrations which vary from as little as 10 −8 m up to at least 10 −2 m. A wide range of rock/fluid ratios is permitted by this alteration mineralogy. Under these conditions solution pH is calculated to vary from 7 to just above 12. Solution Eh is calculated to vary from −0.5 to −0.75 V. We calculate that the mineralogy of the important CI chondrites can be well-reproduced by alteration of either CM or CV anhydrous material. This alteration is calculated to occur best for temperatures of 50 to (at least) 150°C, total solution carbon concentrations varying from approximately 10 −3 to (at least) 10 −2 m, and a wide range of rock/fluid ratios. Under these conditions solution pH is calculated to vary from 7 to between 9 and 10, and Eh from −0.3 to −0.8 V, in the direction of increasing alteration. We therefore conclude that these were the principal conditions of aqueous alteration on the CI parent asteroids. The alteration assemblage observed for the CM chondrites is not produced by alteration of the CV chondrites under the modeling conditions imposed by this study, which suggests that the CM chondrites do not necessarily share the same parent asteroids with the CV chondrites. On a purely mineralogical basis, howerver, the CI chondrites could have been produced from either (or both) CM or CV chondrite material, and therefore be present on either type of parent asteroid.

The reuse of reactive dye liquors using charged ultrafiltration membrane technology

A closed-loop recycle system using a charged ultrafiltration membrane to decolourise reactive dye effluents from a textile yarn and fabric dyeing process is described. The economics of the process depend on the value of the electrolyte ($5 to $10 per M 3). Conventional reactive dyeing technology was examined and modified to facilitate dye liquor reuse. The performance of the membrane was examined in terms of electrolyte rejection, colour rejection and permeate flux under varying conditions of solution pH, ionic strength and operating pressure.

Synthesis and characterization of a new type of heteropolyanion: pentamolybdobis(n-propylarsonate), having two types of crystals under the same pH conditions in the same solution

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTSynthesis and characterization of a new type of heteropolyanion: pentamolybdobis(n-propylarsonate), having two types of crystals under the same pH conditions in the same solutionBenyao Liu, Yihtong Ku, Ming Wang, and Peiju ZhengCite this: Inorg. Chem. 1988, 27, 21, 3868–3871Publication Date (Print):October 1, 1988Publication History Published online1 May 2002Published inissue 1 October 1988https://doi.org/10.1021/ic00294a040RIGHTS & PERMISSIONSArticle Views79Altmetric-Citations29LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (487 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Mechanisms of aluminum tolerance in Triticum aestivum (wheat). V. Nitrogen nutrition, plant-induced pH, and tolerance to aluminum; correlation without causality?

An aluminum-tolerant cultivar ('Atlas-66') and an aluminum-sensitive cultivar ('Scout-66') of Triticum aestivum L. were grown in solution culture under conditions of varying [Formula: see text] and [Formula: see text] supply with or without 75 μM aluminum. Plants grown with a low [Formula: see text] ratio in solution maintained a higher solution pH than plants grown with a high [Formula: see text] ratio. Although root growth of 'Scout-66' was greater under high [Formula: see text], high solution pH conditions, the relative tolerance of the cultivars to Al was unaffected by the [Formula: see text] ratio and by solution pH. The superior Al tolerance of 'Atlas-66' could not be explained solely by its ability to maintain a high solution pH in mixed nitrogen solutions.

Adsorption of Arsenic on Activated Charcoal

This study explores the adsorption behavior of As(III) and As(V) on activated charcoal under the various conditions of solution pH and temperature. The adsorption loading of As(III) remains constant in the pH range from 0.16 to 3.5, while that of As(V) shows a maximum value at pH2.35 when the pH varies from 0.86 to 6.33. The isosteric heat of adsorption for As(III) varies from 4 to 0.75 Kcal/mole and that for As(V), from 4 to 2 Kcal/mole with varying surface loading. The magnitude of these values suggests that the adsorption of arsenic is by physisorption and due to weak forces such as Van der Waals forces. Activated charcoal adsorbs As(V) by 2.5% of its own weight while it absorbs As(III) by 1.2% of its own weight when the equilibrium concentration of each species is 22 × 10−2 molar. Since arsenic has appreciable adsorbability on activated charcoal, this adsorbent may be a viable candidate to be used for removing arsenic from solution. Further studies to determine more information on the selectivity of arsenic over other valuable metal ions and the ones to determine the effects of other cations such as, ferric, calcium, and magnesium ions are suggested as a next step.

Investigation of electrode glass membranes: Proposal of a dissociation mechanism for pH-glass electrodes

Leached surface layers of pH-glass electrode membranes formed in aqueous solutions were investigated by an ion-sputtering method. Reversible formation of steady-state lithium concentration profiles was observed on changing temperature, pH and hydrodynamic conditions of the leaching solution. While new steady-state profiles were reached within periods comparable with times necessary for generating the corresponding layers on fresh membranes, temperature decreases were followed by extremely slow profile changes depending on the temperature difference. The formation of reproducible, thermodynamically defined, pH-dependent Galvani tensions between solutions and pH-electrode membranes, despite the non-equilibrium and non-steady state of their leached surface layers, is explained by the dissociation of ⩾ SiOH groups at the interface between layer and solution which should be an equilibrium independent of layer structure and state.