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Abstract  

Isothermal titration calorimetry has been used to determine the stoichiometry, formation constants and thermodynamic parameters (ΔG o, ΔH, ΔS) for the formation of the citrate complexes with the Mn2+, Co2+, Ni2+ and Zn2+ ions. The measurements were run in Cacodylate, Pipes and Mes buffer solutions with a pH of 6, at 298.15 K. A constant ionic strength of 100 mM was maintained with NaClO4. The influence of a metal ion on its interaction energy with the citrate ions and the stability of the resulting complexes have been discussed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Y. Suzuki, T. Nankawa, T. Yoshida, T. Ozaki, T. Ohnuki, A. J. Francis, S. Tsushima, Y. Enokida, and I. Yamamoto

Summary  

We have investigated the structure of Eu(III)-citrate complexes in aqueous solution and their degradability by Pseudomonas fluorescens. Analysis of 1:1, 1:2, and 1:5 Eu(III):citrate solutions at pH 7 by electrospray ionization mass spectrometry (ESI-MS) showed that the 2:2 Eu(III)-citrate complex is the predominant complex species at a low citrate/Eu(III) ratio, while at a high ratio, a 1:2 Eu(III)-citrate complex is formed preferably. Studies on the biodegradation of Eu(III)-citrate complex by P. fluorescens have shown that a 2:2 Eu(III)-citrate complex is resistent to degradation while a 1:2 complex transforms to a 2:2 complex with the degradation of excess citric acid.

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Abstract  

By using the isothermal titration calorimetry (ITC) technique, thermodynamic parameters have been determined for reactions of the Mg2+, Ca2+, Sr2+, and Ba2+ ions with the citrate anion. The measurements were run in the Cacodylate, Pipes and Mes buffer solutions of a pH of 6, at 298.15 K, as well as in the Tricine, Tapso, and Tris–HCl buffer solutions of a pH of 8. Further, based on the results of potentiometric titration, the conditional stability constants were determined for the citrate complexes at both pH values. The effect of the reaction environment and the metal ion identity on the interaction energy with the citrate ligand and the stability of the resulting compounds have been discussed.

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Abstract  

A method for preparing99mTc-citrate complex, using instantly formed cuprous ions for the reduction of pertechnetate is described. The labelling kinetics, formation rate and stability of99mTc-Cu-citrate complex were studied. Gel filtration using column scanning technique has been found to be a reliable and unique tool for determining the amount of99mTc-fractions as a function of time in the preparation. The kidney uptake and excretion characteristics suggest a potential usefulness of99mTc-Cu-citrate complex for renal function studies. The safety measures for the amount of the complex to be injected in man have been estimated.

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Abstract  

Cobalt ferrite was synthesised by the thermal decomposition of a citrate precursor through a novel self-propagating combustion reaction (SPCR) and the progress of this reaction is explained. Cobalt ferrite obtained by this reaction is compared with the products obtained by heat treatment of the citrate complex. The thermal behaviour and structures of the precursor, the synthesised ferrite, and the other decomposition products are investigated.

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A strain of Saccharomyces cerevisiae used in the food industry was propagated in the presence of zirconium ascorbate or zirconium citrate complex. The propagation of the yeast was slightly inhibited by zirconium (Zr) in a complex form, but it was not toxic. The Zr content in the fermentation medium decreased faster when using ascorbate complex than the citrate complex. The ascorbate complex was better accumulated by the yeast (4300 mg Zr g-1 dry mass) than the citrate complex (1600 mg Zr g-1 dry mass). The total amino acid content of the yeast cells decreased in the presence of both complexes. The concentration of some amino acids [threonine (Thr), proline (Pro), phenylalanine and cysteine (Cys)] was increased by 10-39% in the medium containing Zr ascorbate, while that of other amino acids [arginine (Arg), serine (Ser), methionine (Met) and glutamic acid (Glu)] decreased by 18-60%. As a result of the presence of zirconium citrate the concentration of Glu, aspartic acid (Asp), leucine (Leu), Thr, valine (Val), Ser, Arg, Pro and Met decreased by 19-32%, and the concentration of Cys increased by 59%.

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Abstract  

A procedure developed for separating and quantifying non protein and protein fractions of aluminum species in urine was applied to four consecutive 24 hr collections of five healthy subjects. The total Al content of urine was determined by a chemical neutron activation analysis technique reported elsewhere. Results from the analysis of all subjects indicate that the majority of aluminum is bound to protein (>88%) with minor fractions as citrate complexes. These data are comparable with other speciation experiments with blood plasma indicating 90% of the aluminum was bound to plasma proteins.

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Abstract  

Dependence upon pH of Ac and Th distribution coefficients between the cation exchange resin and buffer citrate solutions had been investigated; the optimal conditions are suggested for effective separation of the elements in this system. These results are in successful accordance with such conditions calculated on the basement of Ac and Th citrate complex formation constants.The generator method for225 Ac periodical separation from229 Th samples is developed.229 Th storage in solution between separations excludes the contamination of actinium final solution with radiolysis products and provides 100-% yield of this isotope and its high radiochemical purity. The parent nuclide loss after continuous use of the generator does not take place.

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Abstract

In this article, the role of the preparation route and calcinations temperature on the thermal expansion and conductivity of BaCe0.8Y0.2O3−δ (BCY) has been studied. In particular, the samples were synthesized by means of the solid-state reaction and by a sol–gel route. BCY has been suggested as proton conducting electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Proton conductivity strongly depends on the densification of the material as well as the crystal structure, which is generally influenced by the preparation procedure. It was found that a single phase material could be achieved at 1000 °C for the samples prepared through the sol–gel route with ~96% packing density. In case of ceramic route, single phase could be obtained at higher temperatures (1200 °C) and does not lead to good density values. The ceramic synthesis produces BCY material in cubic symmetry where as the gel–citrate complexation route leads to homogenous orthorhombic BCY. The conductivity measurements of sample synthesized by two different routes were investigated by means of impedance spectroscopy and electron microscopy. A comparative study of thermal expansion behavior of BCY synthesized by different route was carried out.

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Abstract  

We reported the synthesis and labeling of one tetradentate and two pentadentate amino-phenol ligands with technetium-99m by the direct pertechnetate addition and by ligand exchange methods. Labeling by direct pertechnetate addition was attended by adding pertechnetate eluate to the ethanolic solution of the amino-phenol ligands at pH 9. Stannous chloride dihydrate was used as reducing agent. Exchange studies were carried out via the use of the following 99mTc-chelates: 99mTc-DTPA, 99mTc-gluconate, 99mTc-tartrate and 99mTc-citrate complexes. Ligand exchange method was achieved by incubation the ligand solutions with 99mTc-co-ligands complexes in 0.05M bicarbonate buffer pH 9. At this pH value the 99mTc-co-ligands dissociated and the more stable new 99mTc-ligands were formed with high radiochemical yield 95%. The radiochemical yield of 99mTc-labeled amino-phenol ligands were estimated by solvent extraction, electrophoresis and HPLC methods. The produced technetium-99m amino-phenol complexes were neutral, lipophilic and stable during the period of 24 hours.

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