Enhancement of organic phase controlled extraction of copper by activated carbon

The addition of activated carbon particles (Darco-G, average size 4.3,μm) is shown to enhance the initial rate of extraction of copper in a Lewis cell by a mixture of α- and β-hydroxyoximes, when the rate of extraction is controlled by resistances in the organic phase. It is likely that the copper complex is adsorbed by carbon near the interace and partially released in the bulk. The enhancing effect of carbon vanishes when toluene is used as a diluent instead of heptane, presumably because toluene preferentially adsorbs on its surface.

Differing estrogen activities in the organic phase of air particulate matter collected during sunny and foggy weather in a Chinese city detected by a recombinant yeast bioassay

Total air suspended particles (PM 100) collected from an urban location near a traffic line in Wuhan, China, were examined for estrogen using a recombinant yeast bioassay. Wuhan, located at the central part of China, is the fourth biggest city in China with 7 million populations. Today, Wuhan has developed into the biggest city and the largest traveling center of central China, becoming one of the important bases of industry, education and research. Wuhan is right at the confluent point of Yangzi River, the third longest river in the world, and its largest distributary Hanjiang, with mountains and more than 100 takes in downtown area. Therefore, by its unique landscape, Wuhan has formed clear four seasons with relatively long winter and summer and short spring and autumn. Foggy weather usually happen in early spring. The yeast line used in this assay stably expresses human estrogen receptor-alpha. Weak but clear estrogenic activities were detected in the organic phase of crude extracts of air particle materials (APM) in both sunny and foggy weather by 0.19-0.79 mug E2/gPM(100) which were statistically significantly elevated relative to the blank control responding from 20% to 50% of the maximum E2 response, and the estrogenic activity was much higher in foggy weather than in sunny weather. The estrogenic activities in the sub-fractions from chromatographic separation of APM sampled in foggy days were also determined. The results indicated that the responses of the fractions were obviously higher than the crude extracts. Since there is no other large pollution source nearby, the estrogenic material was most likely from vehicle emissions, house heating sources and oil fumes of house cooking. The GC/MS analysis of the PM100 collected under foggy weather showed that there were many phenol derivatives, oxy-PAHs and resin acids which have been reported as environmental estrogens. These results of the analysis of estrogenic potency in sunny and foggy weather in a subtropical city of China indicate that further studies are required to investigate the actual risks for the associated health and atmospheric system. (C) 2004 Elsevier Ltd. All rights reserved.

Organic-phase enzyme electrode for phenolic determination based on a functionalized sol-gel composite

An amperometric biosensor for monitoring phenols in the organic phase was constructed by the silica sol-gel immobilization of tyrosinase on a glassy carbon electrode. The organic-inorganic hybrid materials with different sol-gel precursors and polymers were optimized, and the experimental conditions, such as the effect of the solvent, operational potential and enzyme loading were explored for the optimum analytical performance of the enzyme electrode. The biosensor can reach 95% of steady-state current in about 18 s, and the trend in the sensitivity of different phenols is as follows: catechol > phenol >p-cresol. In addition, the apparent Michaelis-Menten constants (K-m(app)) and the stability of the enzyme electrode were discussed. (C) 2000 Elsevier Science S.A. All rights reserved.

The effect of substrate and solvent properties on the response of an organic phase tyrosinase electrode

The responses of a cryohydrogel tyrosinase enzyme electrode to four substrates in three pure water immiscible organic solvents were investigated. Kinetic parameters, the maximum kinetic current, I-max, the apparent Michaelis-Menten constant, K-m(app), and I-max/K-m(app), were calculated. The I-max/K-m(app) value was taken as an indicator of the catalytic efficiency of the sensor. The effect of the substrate hydrophobicity on I-max/K-m(app) and response time of the sensor were discussed. The effects of both hydrophobicity (log P) and dielectric constant (epsilon) of the organic solvent on the catalytic efficiency of the enzyme in the organic phase were studied. (C) 1997 Elsevier Science S.A.

Organic phase enzyme electrodes based on organohydrogel

A dimethylformamide-polyhydroxyl cellulose organo-hydrogel has been prepared, and its applications for enzyme immobilization in construction of organic phase biosensors have been exploited. With horseradish peroxidase, tyrosinase, and bilirubin oxidase immobilized in the organohydrogel, enzyme electrodes can be operated in various situations, including aqueous buffer, oil/water mixtures, and anhydrous organic solvents, and even in dimethylformamide, to determine analytes of different solubilities, e.g., organic peroxides, phenolic compounds and bilirubin. Biosensing has no restrictions in terms of measuring media and solubilities of analytes.

Amperometric biosensor for tyrosinase inhibitors in a pure organic phase

The determination of benzoic acid, thiourea and 2-mercaptoethanol in three pure organic solvents, viz., chloroform, chlorobenzene and 1,2-dichlorobenzene, by using an amperometric cryohydrogel tyrosinase biosensor is described. Measurements were carried out with phenol as the enzyme substrate. Kinetic parameters (K-i and I-50) were determined in the three solvents for various inhibitors. The sensor showed the most sensitive measurements to these inhibitors in pure chloroform. The solvent-induced deviation of the biosensor to thiourea was evaluated by means of Hill coefficients. The smallest deviation as observed in 1,2-dichlorobenzene, owing to the high hydrophobicity of this solvent. The nature of the inhibition process and its reversibility mere also examined.

CONSTRUCTION OF A TYROSINASE-BASED BIOSENSOR IN PURE ORGANIC-PHASE

A novel immobilization method for construction of a tyrosinase-based biosensor applied in pure organic phase is described. This method gives the enzyme a hydrated shell which allows the enzyme to maintain its biocatalytic activity in a pure organic solvent The enzyme electrode was used to determine several phenols and o-diphenols in pure chloroform and chlorobenzene. The biosensor can be stored in dry state for more than 3 months without any loss of the activity. The kinetic parameters have also been calculated and are presented herein.

AN ORGANIC-PHASE ENZYME ELECTRODE BASED ON AN APPARENT DIRECT ELECTRON-TRANSFER BETWEEN A GRAPHITE ELECTRODE AND IMMOBILIZED HORSERADISH-PEROXIDASE

A mediatorless horseradish peroxidase (HRP) enzyme electrode operated in nonaqueous media is constructed by cryohydrogel immobilization.

ORGANIC-PHASE ENZYME ELECTRODE OPERATED IN WATER-FREE SOLVENTS

A new material, polyhydroxyl cellulose, and a refrigerating immobilization method were used to construct HRP-mediator electrode for determination of hydrogen peroxide in water-free organic solvents. Rapid and sensitive response was obtained. The enzyme el

Influence of cerium (IV) ions on the inorganic and organic phase for preparation of a siloxane-PMMA based film on tin plate substrate

Tinplate is one of the most widely used food canning materials, however, there are significant problems related to the use of tinplate cans, such as alterations in sensory features affecting food quality and corrosion phenomena of the canning material. To avoid corrosion problems different methods have been used for the passivation of tinplate such protective lacquers or different kinds of corrosion inhibitors (chromate and dichromate). However, chromates and dichromates are extremely harmful to the environment and can cause carcinogenic tumors to humans. An option, protective coatings obtained by the sol-gel process, act as a physical barrier, which isolates the surface of metal protecting from the corrosive agents. The aim of this work is to study the influence of addition of cerium (IV) ions in the inorganic and organic part of sol-gel processing in the formation of hybrid coatings based on siloxane-PMMA on tin plate. The coatings were obtained by dip-coating technique and evaluated by open circuit and impedance measurements, linear polarization and polarization curves obtained in 3.5% NaCl solution. The results have clearly shown the improvement on the protective properties of the Ce 4+ modified film when added into the organic phase, which can be due to the formation of a more uniform and densely reticulated siloxane-PMMA film. © 2009 by NACE International.

Gas-liquid interfacial area in stirred vessels: The effect of an immiscible liquid phase

The presence of an inert immiscible organic phase in gas�liquid dispersions in stirred vessels influences the interfacial area in a more complex fashion than hitherto reported. As the organic phase fraction is increased, the interfacial area expressed on the basis of a unit volume of dispersion or aqueous phase, first increases, passes through a maximum and then decreases. This trend is observed irrespective of whether the area is determined by chemical means or by physical method. It is found that for low values of inert phase fraction, the average bubble size decreases whereas the gas holdup increases, resulting in increased interfacial area. The lower average bubble size is found to be due to partial prevention of coalescence as the bubbles size generated in the impeller region actually increases with the organic phase fraction. The actual values of interfacial areas depend on the nature of the organic phase. It is also found that the organic phase provides a parallel path for mass transfer to occur, when the solubility of gas in it is high.

Adsorption and Unfolding of Lysozyme at a Polarized Aqueous-Organic Liquid Interface

The adsorption of proteins at the interface between two immiscible electrolyte solutions has been found to be key to their bioelectroactivity at such interfaces. Combined with interfacial complexation of organic phase anions by cationic proteins, this adsorption process may be exploited to achieve nanomolar protein detection. In this study, replica exchange molecular dynamics simulations have been performed to elucidate for the first time the molecular mechanism of adsorption and subsequent unfolding of hen egg white lysozyme at low pH at a polarized 1,2-dichloroethane/water interface. The unfolding of lysozyme was observed to occur as soon as it reaches the organic−aqueous interface,which resulted in a number of distinct orientations at the interface. In all cases, lysozyme interacted with the organic phase through regions rich in nonpolar amino acids, such that the side chains are directed toward the organic phase, whereas charged and polar residues were oriented toward the aqueous phase. By contrast, as expected, lysozyme in neat water at low pH does not exhibit significant structural changes. These findings demonstrate the key influence of the organic phase upon adsorption of lysozyme under the influence of an electric field, which results in the unfolding of its structure.

On the Mechanism of Phase Transfer Catalysis in Brust-Schiffrin Synthesis of Metal Nanoparticles

The two-phase Brust-Schiffrin method (BSM) is used to synthesize highly stable nanoparticles of noble metals. A phase transfer catalyst (PTC) is used to bring in aqueous phase soluble precursors into the organic phase to enable particle synthesis there. Two different mechanisms for phase transfer are advanced in the literature. The first mechanism considers PTC to bring in an aqueous phase soluble precursor by complexing with it. The second mechanism considers the ionic species to be contained in inverse micelles of PTC, with a water core inside. A comprehensive experimental study involving measurement of interfacial tension, viscosity, water content by Karl-Fischer titration, static light scattering, H-1 NMR, and small-angle X-ray scattering is reported in this work to establish that the phase transfer catalyst tetraoctylammonium bromide transfers ions by complexing with them, instead of encapsulating them in inverse micelles. The findings have implications for particle synthesis in two-phase methods such as BSM and their modification to produce more monodispersed particles.

Molecular dynamics insight to phase transition in n-alkanes with carbon nanofillers

The present work aims to investigate the phase transition, dispersion and diffusion behavior of nanocomposites of carbon nanotube (CNT) and straight chain alkanes. These materials are potential candidates for organic phase change materials(PCMs) and have attracted flurry of research recently. Accurate experimental evaluation of the mass, thermal and transport properties of such composites is both difficult as well as economically taxing. Additionally it is crucial to understand the factors that results in modification or enhancement of their characteristic at atomic or molecular level. Classical molecular dynamics approach has been extended to elucidate the same. Bulk atomistic models have been generated and subjected to rigorous multistage equilibration. To reaffirm the approach, both canonical and constant-temperature, constant-pressure ensembles were employed to simulate the models under consideration. Explicit determination of kinetic, potential, non-bond and total energy assisted in understanding the enhanced thermal and transport property of the nanocomposites from molecular point of view. Crucial parameters including mean square displacement and simulated self diffusion coefficient precisely define the balance of the thermodynamic and hydrodynamic interactions. Radial distribution function also reflected the density variation, strength and mobility of the nanocomposites. It is expected that CNT functionalization could improve the dispersion within n-alkane matrix. This would further ameliorate the mass and thermal properties of the composite. Additionally, the determined density was in good agreement with experimental data. Thus, molecular dynamics can be utilized as a high throughput technique for theoretical investigation of nanocomposites PCMs. (C) 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.