Electrokinetic studies on testosterone/aqueous electrolyte interface : Part 1. Electro-osmosis,electrophoresis, streaming potential and streaming current

The electrical properties of testosterone interfaces were investigated. For this purpose, measurements of electro-osmosis, hydrodynamic permeation, streaming potential and streaming currents of metabolically important solutions of the electrolytes NaCl, KCl and MgCl₂ (in the concentration range 10^?4?10^?3 mol/l) across a testosterone plug were carried out. Electrophoretic mobility of testosterone particles suspended in these electrolyte solutions was also studied. The data were analysed from the viewpoint of nonequilibrium thermodynamics. Phenomenological coefficients were evaluated from the linear transport equations and Saxen's relationship was verified. Dependence of phenomenological coefficients on electrolyte concentration was examined. Electro-osmotic and electrophoretic transport coefficients were found to vary linearly with concentration, whereas hydrodynamic permeation and membrane conductance coefficients show non-linear variation. The results are explained on the basis of structural modifications occurring during the passage of the permeating species through the membrane. The nature of the electrical double layer formed at the testosterone/solution interface was ascertained on the basis of the direction of electro-osmotic permeation and electrophoretic migration of testosterone particles.Zeta potentials were estimated in order to obtain a plausible picture of the electrical double layer at the testosterone/solution interfaces. Dependence of zeta potentials on concentration was examined and membrane parameters calculated. The double layer thickness was estimated, which reveals that the diffuse double layer is more compact in the case of MgCl₂ than in that of KCl.     

Extraction studies of thorium(IV) with triphenylphosphine oxide

A simple method is described for the solvent extraction of thorium. Thorium is extracted quantitatively from 5·10^–3M sodium salicylate solution at pH 2.5–3.25 using 2.16·10^–2M triphenylphosphine oxide as an extractant dissolved in toluene. The extracted metal ion is stripped with hydrochloric acid (0.1M) and determined spectrophotometrically with Thoron-1 at 540 nm. The method permits separation of thorium from lanthanum, cerium, neodymium, samarium and uranium from binary mixtures and is applicable to the analysis of monazite sand. The method is precise, accurate and selective.     

Electrokinetic sorting and collection of fractions for preparative capillary electrophoresis on a chip

A microfabricated device capable of selecting and collecting multiple components from a mixture separated by capillary electrophoresis (CE) is described. This collection is automated and can be easily controlled by a set of rules defined by an operator, enabling fast and consistent operation. The device consists of an electrokinetically steered fluidic network that can be divided into three sections: a CE part, a fractions distribution region and a set of storage channels. Sample fractions leave the CE channel and are detected in the interfacial region by fluorescence intensity measurements. If an upcoming peak is detected, separation is withheld and the potentials are reconfigured to force the fraction into one of the collection channels, where they become available for further processing or analysis. The sequence of separation and collection is repeated until all the bands of interest are captured. A mixture of three fluorescent dyes (Rhodamine 6G, Rhodamine B and Fluorescein) was used to demonstrate the principle. The components were repeatedly separated by means of CE and pooled in their respective storage channels. In comparison to previous developments, the system presented in this paper offers automatic collection of all fractions in a single run. Furthermore, it is possible to run the system in a repetitive mode for accumulative pooling if more fractionated sample is required.     

Matrix infrared spectra and theoretical studies of thorium oxide species: ThOx and Th2Oy

Infrared spectra of three new thorium oxide species have been obtained in argon and neon matrixes. All of the products are experimentally characterized using isotopic oxygen samples with the aid of electronic structure calculations. Ground state thorium atoms react with O(2) to form the ThO(2) molecules, which can dimerize to give Th(2)O(4) products. Th(2)O(4) is predicted to have nonplanar C(2h) symmetry for its closed shell singlet ground state. The rhombus-shaped Th(2)O(2) molecule in the (1)A(g) (D(2h)) ground state is also observed and its formation is proposed via the reaction of Th(2) with O(2). In addition, electron capture of neutral thorium dioxide results in the formation of the ThO(2)(-) anion. It is predicted to have a doublet ground state with a geometry similar to that of the neutral ThO(2) molecule. Electronic structure calculations on the unobserved Th(2)O and Th(2)O(3) molecules are also provided.     

The development of fluoride-sensitive membrane electrodes : Part I. Membranes containing thorium,lanthanum or calcium fluoride

Fluoride-sensitivc membrane electrodes of the Pungor type are described. In these electrodes, a fluoride precipitate is incorporated in a silicone rubber membrane; fluorides of thorium, lanthanum and other rare earths, and calcium have been examined. The method of preparing the precipitate is important; an excess of metal is vital for correct functioning of the final electrode. The most reliable results were obtained with calcium fluoride electrodes, though their sensitivity was less than that of the best lanthanum fluoride electrodes. With these electrodes, linear responses are obtained in the l0^-2–10^-4M fluoride range.     

Electrokinetic studies of cellulosic fibres I. Zeta potential of fibres dyed with reactive dyes

Summary The influence of reaction between a reactive dye molecule and cotton cellulose on the zeta potential of the cellulosic fibres has been studied by streaming potential method. As a result of such a reaction the negative value of zeta potential was decreased and the extent of this decrease was proportional to the amount of dye entered into the reaction. With respect to the influence of various structural features of a reactive dye molecule on the zeta potential of dyed fibres, it was observed that the zeta potential was independent of the type of reactive system but was very much dependent on the number of –SO₃H groups in the dye molecule and the chemical constitution of the chromophoric system in the dye structure.A bifunctional reactive dye (Remazol Black B —C. I. Reactive Black 5) has been shown to form crosslinks between cellulose chains and bring about considerable lowering of negative zeta potential of the dyed fibres as compared to the equivalent amount of same dye but in the modified form to act as a monofunctional reactive dye. This bifunctional dye was also observed to induce H-bonding in the vicinity of the sites of cross-links. Trichloropyrimidine type of dyes have been found to be neither completely monofunctional nor fully bifunctional but seem to lie in between the monofunctional and bifunctional types of dyes.

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Zusammenfassung Der Einfluß der Reaktion zwischen einem reaktiven Farbstoffmolekül und Baumwollzellulose auf das-Potential der Zellulosefasern wurde mit der Strömungspotential-Methode untersucht. Als Ergebnis einer solchen Reaktion sank der negative-Potentialwert ab, und die Abnahme war proportional dem Betrag an Farbstoff, der in Reaktion trat. Im Hinblick auf den Einfluß verschiedener struktureller Eigenschaften eines reaktiven Farbstoffmoleküls auf das-Potential der gefärbten Faser wurde festgestellt, daß letzteres unabhängig vom Typ des Reaktions-systems war, abet sehr abhängig von der Zahl der –SO₃H-Gruppen im Farbstoffmolekül und der Konstitution des chromophoren Systems.Ein zweifunktionaler reaktiver Farbstoff (Remazol Black B — C. I. Reactive Black 5) bildet Vernetzungen zwischen Zelluloseketten und erniedrigt beträchtlich das negative-Potential der gefärbten Fasern, verglichen mit einem Farbstoff in modifizierter Form, so daß er als monofunktioneller Farbstoff wirkt. Dieset zweifunktionale Farbstoff induziert auch Wasserstoffbrücken in der Nachbarschaft der Vernetzungsstellen. Farbstoffe von Trichlorpyrimidin-Typ sind weder streng monofunktionell noch voll bifunktionell. Sie liegen in der Mitte.

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With 11 figures     

Effect of the thorium oxide content on the leaching of a mixed thorium-uranium oxide fuel

Journal of Radioanalytical and Nuclear Chemistry - Leaching of uranium from uranium oxide fuel in contact with water can be a radiation hazard problem in the case of fuel cladding failure, either...     

Solvent extraction studies on thorium sulphate and halides

The effect of water-miscible alcohols, acetone and haloacids in the aqueous phase of sulphuric acid solutions has been studied on the extraction of thorium sulphate and halides by bis(2-ethylhexyl) phosphoric acid (HDEHP) and tri-n-butyl phosphate (TBP). The partition coefficient (E) is greatly affected by these additives, and this gives useful separations from many other elements. Besides, the log-log relationship between the E values and solvent concentration leads to some suggestions on the extraction mechanisms of this mixed system.     

Extraction studies of uranium(VI) and thorium(IV) with tributylphosphine oxide

Clay minerals occur widely in nature and play a very important role in agriculture, mineral recovery and chemical manufacturing. Among the many properties which affect clay behaviour, water binding and ion exchanging appear to be the most important. The study of the cation exchange capacity of soils is of great theoretical and practical importance since the CEC determines in many ways the behavior of nutrients, chemical amendments, and many toxic compounds entering the sols. Sorption interactions with montmorillonite and other clay minerals in soils are potantially important mechanisms for attenuating the mobility of heavy metal cations through the subsurface environment. In this work the cation exchange capacity (CEC) of montmorillonite from west Anatolia, and sorptions with montmorillonite for attenuating the mobility of uranium were studied. The CEC value was found to be 77 meq/100 g montmorillonite. The relative importance of test parameters e.g., contact time, particle size, pH and U(+6) aqueous speciation was determined. The results show that sorption on montmorillonite is a funtion of pH depending strongly on the aqueous U(+6) species. It reaches a maximum at near neutral pH(pH}7). At low and at high pH solutions the sorption values of uranium are poor. These sorption values were attributed to the formation of aqueous U(+6) carbonate complexes in alkaline conditions and the ionexchange process between UO₂ ⁺² species and interlayer cations on montmorillonite in acidic solutions.     

Electrokinetic characterization of a microporous non-commercial polysulfone membrane: phenomenological coefficients and transport parameters

Electrical and electrokinetic phenomena (electrical resistance, streaming potential and membrane potential) in a porous polysulfone membrane was studied in the framework of the linear thermodynamics of irreversible processes and the phenomenological coefficients were determined for different concentrations of NaCl and MgCl₂ solutions (10⁻³M<5×10⁻²M). From experimental values, other characteristic membrane parameters such as the concentration of fixed charge in the membrane (=−3×10⁻³M), the ionic transport numbers and permeabilities through the membrane (t(Na⁺)=0.392 and t(Mg⁺²)=0.363; P(Na⁺)=3.5×l0⁻⁸m/sec and P(Mg⁺²)=2.9×10⁻⁸m/sec) were also obtained. Membrane surface-electrolyte solution interface was characterized by zeta potential values. The effect of both salt concentration and pH on zeta potential results was also studied.     

The band structure of submonolayer thorium coatings on a silicon oxide surface

Data are reported on the electronic structure of thorium-containing clusters formed on the surface of natural silicon oxide via electrochemical deposition. The mutual arrangement of bands in the clusters and silicon oxide substrate is restored with the use of X-ray photoelectron spectroscopy and electron energy loss spectroscopy. It is concluded that the studied cluster/substrate system may be promising for investigating the low-lying isomeric nuclear transition in ²²⁹Th isotope.     

Electrokinetic migration of acidic drugs across a supported liquid membrane

Electrokinetic cross membrane extraction of acidic drugs was demonstrated for the first time. The acidic drugs were extracted from an alkaline aqueous donor solution (300 microl), through a thin supported liquid membrane of 1-heptanol sustained in the pores of the wall of a porous hollow fiber, and into an aqueous alkaline acceptor solution (30 microl) present inside the lumen of the hollow fiber by the application of a d.c. electrical potential. The negative electrode was placed in the donor solution, and the positive electrode was placed in the acceptor solution. Optimal extractions were accomplished with 1-heptanol as the supported liquid membrane, with 50 V as the driving force, and with pH 12.0 in both the donor and acceptor solutions, respectively (NaOH). Equilibrium extraction conditions were obtained after 5 min of operation with the whole assembly agitated at 1200 rpm. Eleven different acidic drugs were extracted with recovery values between 8 and 100%, and initial data supported that electrokinetic cross membrane extraction provided repeatable data and linear response between original donor concentration and final acceptor concentration of the acidic model compounds.     

Conductometric studies on the precipitation of thorium hydroxide

This paper presents the effect of age on the conductance of hydroxide precipitated from thorium chloride with progressive addition of alkali. The effect of age on reverse titration has also been studied. Conductance study on the aged samples reveals that in every case there is at first a decrease in the electrical conductance of mixture and then an increase on prolonged ageing. This phenomenon is more marked with the concentrated solutions where it is presumed that adsorption of ions is more marked resulting in the diminution of electrical conductance. With dilute solutions, the precipitated mass being very small in amount does not adsorb appreciable amount of electrolytes from the system. On prolonged ageing there is a decrease of the surface reactivity of the precipitated mass, resulting in the release of adsorbed electrolytes and hence the increase in conductance of the system.

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Zusammenfassung Diese Arbeit behandelt die Wirkung der Alterung auf die Leitfähigkeit von Hydroxid, ausgefällt aus Thoriumchlorid mit fortschreitender Zufügung von Alkali. Auch der Alterungseinfluß auf den umgekehrten Vorgang: Zufügung von Thoriumchlorid zu Alkali, wurde untersucht. Die Leitfähigkeitsmessungen an gealterten Proben zeigen, daß zunächst stets eine Abnahme der elektrischen Leitfähigkeit der Mischungen und später eine Zunahme mit fortschreitender Alterung stattfindet. Dieses Phänomen ist für konzentriertere Lösungen ausgeprägter, bei denen ja wohl auch die Adsorption der Ionen stärker ist und damit die Abnahme der elektrischen Leitfähigkeit. Bei verdünnten Lösungen adsorbiert die dem Betrag nach sehr kleine ausgefällte Masse keine wesentlichen Beträge von Elektrolyten aus dem System. Mit verlängerter Alterung findet eine Abnahme der Oberflächenreaktivität des Fällproduktes statt, was die Freigabe von adsorbierten Elektrolyten und damit eine Zunahme der Leitfähigkeit des Systems zur Folge hat.

     

Electrometric studies on the precipitation of thorium hydroxide

Summary On the ageing of thorium hydroxide, there is considerable change in the p_H of the system. Increase of p_H is a result of release of hydroxyl ions and decrease of p_H indicates the release of hydrogen ions from the adsorbent. Ageing before inflexion point especially with larger alkali leads to the coagulation of thorium hydroxide which eventually increases the p_H of the medium.

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Zusammenfassung Mit Alterung von Thoriumoxid treten betr?chtliche ?nderungen im p_H der Systeme auf. Der Anstieg des p_H ist ein Ergebnis des Freiwerdens von HydroxylIonen, die Abnahme zeigt das Freiwerden von Wasserstoff-Ionen vom Adsorbenten an. Alterung unterhalb des Inflexionspunktes, besonders mit gr?\erem Alkali-Gehalt, führt zur Koagulation des Thoriumhydroxids, was schlie\lich das p_H des Mediums vergr?\ert.

     

Free flow electrophoresis for the purification of proteins: I. Zone electrophoresis and isotachophoresis

The principles and some applications of free flow zone electrophoresis and isotachophoresis are described. The influence of (i) carrier electrolyte conductivity on the migration velocity and (ii) band shape on zone electrophoresis was investigated. The technique was found convenient for studying the effect of pH on the mobility of proteins to create a mobility curve. The purification of alcohol dehydrogenase from a crude yeast extract revealed the separation power of zone electrophoresis for complex protein mixtures. Without additional steps, a purification factor of 5.4, with a recovery of 97% alcohol dehydrogenase, was achieved. Free flow isotachophoresis was applied to the purification of immunoglobulins from human serum. Disadvantages of this technique are the time-consuming development of an optimized separation system and the empirical search for suitable spacers. Also, reaching of the steady state becomes increasingly difficult as the number of sample components increases.     

Conductometric studies on the precipitation of thorium hydroxide

The adsorption of stabilising ion H⁺ has been determined for a precipitate of hydrous ferric oxide and that of SO₄″ for the positively charged sol of hydrous ferric oxide during its coagulation as affected by potassium sulphate in presence of various non-electrolytes. The adsorption of both the stabilising and coagulating ions decreases in presence of ethyl alcohol and acetone, an increase is, however, observed in presence of glucose and urea. With gelatin at lower concentration the adsorption of both H⁺ and SO₄″ decreases whilst the reverse is noticed at higher concentrations. It is concluded that the cutting down of the adsorption of either the stabilising or the coagulating ion cannot explain sensitisation or stabilisation.     

Coated wire thorium ion selective electrode: Part I

Coated wire ion selective electrode for thorium ion selective potentiometry was developed. Thorium ion selective coated wire electrodes were prepared by depositing a membrane comprising of Aliquat-336 loaded with Th(NO₃)₆²⁻ ions and poly vinyl chloride in varying proportion. A linear near-Nernstian response with a slope of −29.5 ± 0.3 mV over thorium concentration range of 1 × 10⁻¹–3 × 10⁻⁵ M in constant total nitrate concentration of 6 M was obtained for the electrodes of almost all the composition studied. In spite of small drift in response potential from composition to composition, day to day as well as from electrode to electrode, the slope of potential response line was constant within experimental error. Moreover, the electrode once prepared could be conveniently used over a period of one and half month.     

Some phosphine oxide complexes of thorium and uranium tetrabromides

Trimethyl phosphine oxide (tmpo) complexes, MBr₄(tmpo)₆ (M = Th and U) have been prepared by reactions in non-aqueous solvents. Some chemical properties, i. r., and the u. v. visible spectra of uranium complex are reported.