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Abstract

TG-DTG-DTA has been used to characterize various isomers of CoCl2·2(CH3C6H4NH2). Thermal analysis is further used to analyse the binary mixtures of these isomers. DTA recorded after different elapsed times follows the progress of reaction between cobalt chloride and benzocaine where progressively small endotherms are associated with starting materials. The application of thermal analysis to following the solid-solid reactions between metal acetates and 8-hydroxyquinoline was highlighted. The stoichiometry of such reactions was confirmed from the decrease in intensity of an endotherm as one increases the stoichiometry.

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Abstract  

A rapid radiochemical procedure based on the removal of mercury, selenium, arsenic and antimony by columns of C18-bonded silica gel or activated carbon after their selective complexation in sulphate/nitrate media by ammonium pyrrolidine-dithiocarbamate, diethylammonium diethyldithiocarbamate, potassium ethyl xanthate, bismuthiol II or 8-hydroxyquinoline, was examined. Comparisons were made of the ability of the two ion retention media to remove these metal ions and to allow their regeneration and recycling. The effectiveness of this technique was demonstrated by analysis of horse kidney and human diet, International Atomic Energy Agency biological reference materials, for mercury and selenium.

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A particularly rapid HPTLC method has been established for chromatographic separation and quantification of p -aminobenzoic acid (PABA) in complex dietary supplement tablets. After chromatography, PABA was determined by spectrodensitometry at 270 nm. PABA spots were then visualized by a novel staining procedure involving the Bratton-Marshall coupling reaction after spraying with 8-hydroxyquinoline in situ on the chromatographic plates. After visualization, spectrodensitometric analysis was repeated at 500 nm. Linearity, intermediate precision, sensitivity, accuracy, and precision were compared for both methods. Results from tablet analysis were verified with the modified Bratton-Marshall spectrophotometric procedure.

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Abstract  

We studied the preparation of some specific adsorbers capable of isolating and concentrating actinides. Bases of the 8-hydroxyquinoline family, diphosphineamine and tribenzylamine, salted by benzohydroxamic, benzylic or phthalic acid, are able to complex actinides in different oxidation states. As a result of the presence of the benzene rings, all the compounds are easily incorporated into active charcoal to obtain adsorbers with a highly specific surface. The adsorption behaviors of uranyl U(VI) ion, thorium(IV) and Eu(III) were studied by evaluating their distribution coefficients, K d. Results show that all the prepared salts can adsorb the ions in the III and IV oxidation state from weak acid solutions, whereas uranyl ion is adsorbed mainly from weak basic solutions. The prepared compounds can be used successfully to absorb and concentrate actinides from nearly neutral solutions, such as natural waters. The 8-hydroxyquinoline salt of the benzylic anion showed the highest adsorption values and thus seems to be the most appropriate salt to use in the analysis of actinides in water.

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Abstract  

The adsorption conditions of uranium, neptunium, thorium, europium on the adsorbers containing the benzylate salts of the 8-hydroxyquinoline (adsorber B), and of 2-methyl- 8-hydroxyquinoline (adsorber R), were prepared, supported onto charcoal and compared with an adsorber, containing the benzylic acid, (G), stabilized with d-glucoseamine, and adsorbed onto charcoal as well. Thorium, protoactinium, and europium are adsorbed nearly completely from aqueous solutions at a large pH range, even in low acid medium, whereas uranium and neptunium are completely adsorbed only from basic solutions of pH 9. The actinides are preferentially adsorbed with respect to other ions, which are present in natural waters, such as calcium or magnesium. This feature make the analysis of most actinides in natural waters easily to be performed without changing the pH of the original system. The uranium (neptunium) analysis indeed may be accomplished after adjusting the original pH to a fairly basic value (about to 9). The adsorption experiments from real samples showed that the analysis of the actinides dispersed in natural water systems may be successfully performed after previous concentration on the adsorbers prepare.

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Abstract  

Solvent extractions of thorium(IV) and uranium(VI) by a commercially available chelating extractant LIX-26 (an alkylated 8-hydroxyquinoline) or 8-hydroxyquinoline, benzoic or salicylic acid, dipentyl sulphoxide (DPSO) and their mixtures with butanol as modifier in benzene/methylisobutyl ketone (MIBK) as the diluent have been studied. Extraction of uranium(VI) by 10% LIX-26 and 10% butanol in benzene becomes quantitative at pH 5.0. The pH 0.5 values for the extraction of thorium(IV) and uranium(VI) are 4.95 and 3.35, respectively. Quantitative extraction of thorium(IV) by the mixture of 0.1 M oxine and 0.1 M salicylic acid in methylisobutyl ketone was observed at pH 5.0. The influence of concentration of various anions on the extraction of Th4+ by mixtures of LIX-26 and benzoic acid has been studied. Studies on extraction of thorium(IV) and uranium(VI) by mixtures of LIX-26 (HQ) and DPSO show that the extracted species are possibly of the type [ThQ2/DPSO/2/SCN/2] and [UO2Q2/DPSO/], respectively.

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Abstract  

The ultrafiltration preconcentration of Cd2+ using micellar extraction with 8-hydroxyquinoline (8-HQ), solubilized in anionic micelles of sodium dodecylsulphate (SDS)) were studied. The n-butanol was used as a co-surfactant. Ultrafiltration yields (R, %) on cellulose acetate membranes (wet, 20000 MW-CO) under 400 kPa pressure were determined. Distribution ratios (D) of cadmium between bulk liquid phase and micellar pseudophase were estimated. The constants (app.) for the cadmium-sodium exchange on SDS micelles surface at pH values of 4.8 and 5.3 (3.36 and 3.86, respectively) were determined. It was found, that the values of ultrafiltration yields of the cadmium (at constant concentration of 8-HQ) are influenced not only by the pH and by the concentration values, but also by the ratio of the concentrations of the metal and the anionic surfactant.

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Abstract  

The extraction of bismuth has been investigated in dependence of dilution and stoichiometry, using the reagents 8-hydroxyquinoline, N-benzyl-N-phenylhydroxylamine, diphenylthiocarbazone and substituted carbamates. Stripping of bismuth from organic solutions of the respective chelates using ligands such as EGTA, thioglycollic acid and 2,3-dimercaptopropane-1-sulfonate was also studied. It has been demonstrated that the equations proposed for determining the range of quantitative substoichiometric extraction are valid in the case of bismuth only at concentrations above 10−5 M Bi. At further dilutions (10−6–10−8 M), which would be of major interest in devising analytical methods based on the substoichiometric radioisotope dilution technique for determining bismuth at the trace level, the equilibria are shifted in favour of the competing hydrolytic reactions, so that the extraction is quantitative only with ammonium tetramethylenedithiocarbamate present in excess.

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Abstract  

Magnesium ion was reacted with 5,7-dibromo-, 5,7-dichloro-, 7-iodo-and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium hydroxide medium under constant stirring to obtain (I) Mg[(C9H4ONBr2)2]2H2O; (II) Mg[(C9H4ONCl2)2]3H2O; (III) Mg[(C9H5ONI)2]2H2O and (IV)Mg[(C9H4ONICl)2]2.5H2O complexes. The compounds were characterized by elemental analysis, IR spectra, ICP, TG-DTA and DSC. Through thermal decomposition residues were obtained and characterized, by X-ray diffractometry, as a mixture of hexagonal MgBr2 and cubic MgO to the (I) compound at 850C; cubic MgO to the (II), (III) and (IV) compounds at750, 800 and 700C, respectively.

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Abstract  

A novel combustion method of employing poly(ethylene glycol) with the precursor in a fixed ratio for the synthesis of ultrafine γ-Fe2O3 through a self-propagating combustion synthesis is reported. Four different precursors viz. ferrous hydroxide, ferrous oxalate dihydrate, ferric 8-hydroxyquinoline and ferric acetylacetonate are employed in this study for the conversion of these precursors to ultrafine g-Fe2O3 particles. The as synthesized γ-Fe2O3 samples are characterized by XRD, SEM and thermal techniques. A case study for the synthesis of γ-Fe2O3 employing ferric acetyl acetonate as precursor is reported. The importance of employing thermal analysis techniques in understanding the combustion synthesis is envisaged.

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