Ultramikrobestimmung von Selen(IV) mit Hilfe der Chlorat-Chlorid-Hydrazin-Reaktion

Zusammenfassung Zum katalytischen Nachweis von Selen(IV) wird das Chlorat-Chlorid-Hydrazin-System empfohlen. Die Grenzkonzentration beträgt 0,004g Se/ml, die Grenzverdünnung 1 2,5 · 10^–8.In Ultramikrokonzentration kann Selen(IV) mit der Simultankomparationsmethode oder chronometrisch auf Grund des LandoltEffektes bestimmt werden. V(V), Os(VIII) Cu(II), Mo(VI) und Te(IV) wirken in diesem System ebenfalls katalytisch.

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Ultramicrodetermination of selenium(IV) by use of the chlorate-chloridehydrazine system

Summary Selenium(IV) may be catalytically detected by use of the chlorate-chloride-hydrazine system. This reagent is recommended. The limiting concentration is 0.004g Se/ml, the limiting dilution is 1 2.5 · 10^–8. Ultramicro amounts of selenium(IV) may be determined with the simultaneous comparison method or chronometrically on the basis of the Landolt effect. V(V), Os(VIII), Cu(II), Mo(VI) and Te(IV) likewise have a catalytic effect in this system.

     

One-electron oxidation of organic substrates by oxochloride complex of rhenium(VI) in hydrochloric acid solutions

Photoreduction reactions of Re(VII) in the presence of an electron donor — diphenylamine (DPA) and hydroquinone (HQ) in concentrated hydrochloric acid solutions — were studied using the pulse photolysis method. The short-lived complex of rhenium(VI) ReOCL₅ undergoes one-electron oxidation reactions with both DPA to form a cation-radical DPA^+. and with HQ to form a semiquinone radical. The decay of the cation-radicals DPA^+. proceeds by a second order reaction with the formation of a stable product (_max=590 nm)Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 3, pp. 365–368, May–June, 1987.     

Spectrophotometric and ESR methods of rhenium determination based on one electron photoreduction of Re(VII)

A possibility of photochemical reduction of Re(VII) to Re(VI) in mixture of concentrated sulfuric and hydrochloric acids has been demonstrated. The reaction mechanisms of Re(VII) photoreduction and Re^VIOCl₅ ^– complex decay have been considered from view point of acids and water content. The optimal conditions of Re^VIOCl₅ ^– stability have been found.Spectrophotometric and ESR methods of rhenium determination based on photochemical production of Re^VIOCl₅ ^– complex with the detection limit of 1g/ml have been proposed. Rhenium concentration in industrial sulfuric acid has been determined.     

Separation of rhenium by thin-layer chromatography with polyethyleneimine cellulose in hydrochloric acid media

Summary The thin-layer chromatographic behavior of 49 inorganic ions on polyethyleneimine (PEI) cellulose has been investigated in hydrochloric acid media (0.01–1.0 mol dm⁻³). The sorption on the cellulose decreases with increasing acid concentration for most of the ions, but As(III), Ti(IV) and Te(VI) do not exhibit any R_f variation with the acid concentration. The R_f spectra of TI(I), Cd(II), Pb(II) and Zn(II) have a maximum. Ag(I), Bi(III), Nb(V), Ta(V), Mo(VI) and W(VI) are retained tightly on the layer, due to either insoluble salt formation or extensive hydrolysis. The extremely low R_f values of Hg(II), Pd(II), Au(III), Ru(III) and Pt(IV) are accounted for by stability of their chlorocomplexes. Re(VII) distributes chromatographically, having moderate R_f values between 0.3 and 0.6, so that the selective separation of Re(VII) from the other ions is feasible.     

3-Hydroxy-2-(2-thienyl)-4H-chromen-4-one as a new reagent for the extraction and trace determination of molybdenum(VI)

A simple, sensitive and selective method for the extraction and trace determination of molybdenum(VI) has been developed; it is based on its reaction with 3-hydroxy-2-(2-thienyl)-4H-chromen-4-one (HTC) in sulphuric acid medium. The 1:2 Mo (VI)-HTC yellow complex is quantitatively extractable into chloroform (_max 420 nm) and is stable for more than 4 h. The procedure eliminates the interference of a large number of metal ions and complexing agents. Beer's law is obeyed in the range of 0–2.85 g Mo/mL with a molar absorptivity, Sandell's sensitivity and standard deviation of 5.28×10⁴ L mol^–1 cm^–1, 0.0018 g Mo/cm² and ±0.0054, respectively. The method has successfully been used for the spectrophotometric determination of molybdenum in steel samples.     

Preliminary study of quality control of99m Tc from99Mo generators

The separation of Tc(VII) from Mo(VI) by thin-layer and paper-chromatography is discussed. Some aspects concerning the formation and identification of lower oxidation states of Tc(VII) are also mentioned. Finally, a spot test is recommended for the determination of Mo(VI) and Al, which can be contaminants in the Tc(VII) solution eluted from the⁹⁹Mo column, filled with Al₂O₃.     

HPLC analysis of Cr, V and Mo using pre- in combination with on-column derivatisation by oxine, bipyridine and H2O2

Summary The HPLC behaviours of Cr(VI), Mo(VI) and V(V) peroxo complexes in a H₂O₂-8-hydroxyquinolinebipyridine system were studied by using pre-column in combination with on-column derivatisation. The chromatograms of Cr(VI), Mo(VI) and V(V) show them to be CrO^2– ₄, oxine-Mo peroxo and oxine-V-bipyridine peroxo complexes, respectively, and were used for the separation, identification and determination of Cr(VI), Mo(VI) and V(V) using acetonitrile-water as mobile phase. The calibration curves obtained for 20 l injections were linear for 1.4–7.0 mg/l Cr, 1.3–6.5 mg/l Mo and 0.7–3.4 mg/l V. The relative standard deviations were between 6 and 10%.

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HPLC-Analyse von Cr, V und Mo unter Verwendung von Vorsäulen- in Kombination mit Säulenderivatisierung durch Oxin, Bipyridin und H₂O₂

     

Reduction of Ruthenium(IV) to Ruthenium(III) in Aqueous Alcohol Solutions of Hydrochloric Acid under Microwave Radiation

The behavior of a kinetically inert form of ruthenium(IV), the -oxo-bis-[pentachlororuthenate(IV)] ion [Ru₂OCl₁₀]^4–, was studied in aqueous alcohol solutions of hydrochloric acid under microwave radiation and upon the heating of the solutions. The conditions were selected for the quantitative reduction of ruthenium(IV) to ruthenium(III) with alcohols in 0.6–10 M HCl solutions in a microwave field. The maximum time it takes to reduce ruthenium(IV) under microwave radiation (30 min) was an order of magnitude shorter than that for heating the solutions in a boiling water bath. Regardless of the type of alcohol, the most rapid reduction of ruthenium(IV) was observed at the boundaries of the studied range of hydrochloric acid concentrations. It was found that, under microwave radiation, thermal effects were the driving force of the process in a 0.6 M HCl solution at 98°C, whereas, in 8–10 M HCl solutions, the contributions of nonthermal and thermal effects were comparable. It was shown that the reducing ability of saturated monoatomic C₁–C₄ alcohols increases with the number of carbon atoms and is also due to specific features of microwave radiation.     

Interaction of Aluminium (III) with the f-Family Ions Np(VI), Pu(VI), Np(V), Np(IV), Pu(IV), Nd(III), and Am(III) in the Course of Simultaneous Hydrolysis

The interaction of Np(VI), Pu(VI), Np(V), Np(IV), Pu(IV), Nd(III), and Am(III) with Al(III) in solutions at pH 0–4 was studied by the spectrophotometric method. It was shown that, in the range of pH 3–4, the hydrolyzed forms of neptunyl and plutonyl react with the hydrolyzed forms of aluminium. In the case of Pu(VI), the mixed hydroxoaqua complexes (H₂O)₃PuO₂(-OH)₂Al(OH)(H₂O)₃ ²⁺ or (H₂O)₄PuO₂OAl(OH)(H₂O)₄ ²⁺ are formed at the first stage of hydrolysis. Np(VI) also forms similar hydroxoaqua complexes with Al(III). The formation of the mixed hydroxoaqua complexes was also observed when Np(IV) or Pu(IV) was simultaneously hydrolyzed with Al(III) at pH 1.5–2.5. The Np(IV) complex with Al(III) has, most likely, the formula (H₂O) _n (OH)Np(-OH)₂Al(OH)(H₂O)₃ ³⁺. At pH from 2 to 4.1 (when aluminium hydroxide precipitates), the Np(V) or Nd(III) ions exist in solutions with or without Al(III) in similar forms. When pH is increased to 5–5.5, these ions are almost not captured by the aluminium hydroxide precipitate.     

Sorption of Tc(IV) and Tc(VII) on Soils: Influence of Humic Substances

The technetium sorption behaviour in different samples of soils was studied under aerobic conditions. Tc(VII) was reduced to Tc(IV) by Sn²⁺ ions. About 99% of reduced technetium is absorbed by the soils under investigation. Sorption of TcO₄ ^– was studied in short-term (1-hour) and long-term (1-month) experiments. Sorption of TcO₄ ^– in presence of sodium humate (Aldrich) was generally lower than from pure water (from 99% to 12%) and depends on the depth of origin of the ground. Immobilisation of TcO₄ ^– after sorption on superficial sample of soils was studied by paper chromatography. Oxidation of Tc(IV) in presence of NO₃ ^– and NO₂ ^– (concentration range 10^–1–10^–5 mol·dm^–3) ions was studied as a function of time and concentration of NO₃ ^– and NO₂ ^– ions. The content of Tc(IV) in NO₃ ^– and NO₂ ^– solutions decreases with time (46 hours) relatively slowly.     

Heterocyclic analogs of pleiadiene

The behavior of N-methyl derivatives of perimidine (I), aceperimidine (VI), aceperimidylene (VII), naphth[2,3-d]imidazole (V), benzimidazole (II), and 1H- and 3H-naphth[1,2-d]imidazoles (III, IV) with respect to n-butyllithium was studied. Compounds I and V–VII add n-butyllithium to the C=N bond to give 2-n-butyl-2,3-dihydro derivatives, whereas II–IV are metallated to give 2-lithio derivatives. The different reactivities of I, V–VII, and II–IV are explained by the reduced aromatic character and high polarization of the C=N bond in I and V–VII. The investigated compounds are arranged in the following order with respect to the ease of undergoing basic deuterium exchange at the C-H bond V>II>III>IV>VII>I>VI. There is no correlation between the rate of deuterium exchange and the behavior of I–VII with respect to butyllithium.See [1] for communication XXX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1544–1548, November, 1977.     

Technetium-99m generator based on 12-molybdocerate —99Mo precipitate as column matrix

The preparation of insoluble 12-molybdocerate(IV) from⁹⁹Mo of low specific activity, produced by thermal neutron irradiation of MoO₃, is described. Samples of the material are dried at 50, 100 and 200°C and used as column matrices from which the generated^99mTc activity is periodically eluted with saline solution or saline solution containing 5·10^–5M K₂CrO₄ as an oxidant. The elution yields of^99mTc are high and reproducible (95–81%) with radionuclidic purity 99.98%. Both chemical and radiochemical purity (as TcO ₄ ^– ) of the eluates decrease with increasing drying temperature of the column matrix. Using chromated saline solution as eluent improves the radiochemical purity of the^99mTc eluate.     

Stripping voltammetric determination of traces of technetium with a glassy carbon electrode coated with tri-n-octylphosphine oxide

Technetium(VII) and Tc(IV) are concentrated from 3 M hydrochloric acid media by complexing with tri-n-octylphosphine oxide applied as a thin layer to a glassy carbon electrode. Differential-pulse cathodic stripping voltammetry from 0 V provides a stripping peak for Tc(VII) at ?350 mV (vs. Ag/AgCl). The detection limit after an enrichment time of 10 min is about 1.8×10^?8 M Tc(VII). Technetium(IV) produces a stripping peak near the Tc(VII) peak which can be used for rough estimates of the Tc(VII)/Tc(IV) ratio within limited ranges. Uranium(VI) in equimolar concentrations interferes.     

Ion exchange studies of U(VI) from aqueous Arsenazo-III solutions using AG-2X8, Dowex-50WX8 and Chelex-100 resins

The distribution of U(VI) between the anion exchanger AG-2X8, the cation exchanger Dowex-50WX8 and the chelating resin Chelex-100 and aqueous solutions of Arsenazo-III at different pH values was studied. The concentration of Arsenazo-III was in the range of 1.53·10^–4–1.23·10^–3M. Equilibrium pH was varied from 1.0 to 8.78 while U(VI) original concentration was held constant at 3.39·10^–4M. The effect of Arsenazo-III concentration and the variation of hydrogen ion concentration on U(VI) species formed in solution as well as the sorbed species was discussed. Use was made of IR spectroscopy to investigate the sorption behavior. The sorption of some interfering ions such as Th(IV), Zr(IV) and Ce(III) on the resins used at optimum conditions for the sorption of U(VI) was also investigated.     

Rapid and sensitive determination of pertechnetate in99Mo/99mTc generator eluates by reversed-phase high-performance liquid chromatography

Reversed-phase high-performance liquid chromatography with u.v. detection was applied for rapid and sensitive determination of pertechnetate in⁹⁹Mo/^99mTc generator eluates, using a mixture solvent of acetonitrile and 0.04M aqueous acetate buffer (1/1) containing a few volume percentage of 0.5 M tetra-n-butylammonium hydroxide as the mobile phase. Employing a -bondapak C₁₃ column, the TcO ₄ ^– species was separated, monitored with absorbance at 254 nm, and observed at the retention time of 3.5 min. The detection limit was found to be 5.2·10^–10 g of Tc for each injection. Total Tc contents in the^99mTc eluates from clinically-used⁹⁹Mo/^99mTc generator were analyzed by this technique. The^99mTc (⁹⁹Tc) species was separated from the contaminant⁹⁹Mo. This method was found to be useful for the purification of^99mTc (⁹⁹Tc) as well as the determination of total Tc content.     

Investigation of the structure and stability of α-substituted cyclopropyl carbanions by semiempirical quantum-chemical methods

The cyclopropyl carbanions C₃H₄X^– (X=H (I), F (II), Cl (III), CF₃ (IV), COCH₃ (V), CN (VI), NO₂ (VII), which are formed by the removal of a proton at the position, were calculated by the semiempirical MINDO/3 and MNDO methods with full optimization of the geometry. The MINDO/3 method, in agreement with the results from nonempirical methods and experimental data, leads to a nonplanar configuration at the anionic center; the angle between the CX bond and the CCC plane was 58–62°. In all probability the conclusion about a planar structure for all the investigated carbanions except (II), which emerges from the MNDO calculations, is unreliable. By calculation of the change of energies in the isodesmic reactions C₃H₅ ^– + C₃H₅X C₃H₄X^– + C₃H₆ it was found that substitution of hydrogen by the polar substituent X stabilizes the carbanion. On the basis of an analysis of the changes in the length of the cyclic and extracyclic bonds in the transition from the neutral molecule to the carbanion it was established that the introduction of substituents N0₂, COCH₃, and CN into the carbanion gives rise to predominant donation of electron density along the system through the ring to the substituent while the introduction of a halogen leads to transfer of electron density from the substituent to the anionic center.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 5, pp. 590–594, September–October, 1985.     

Simultaneous determination of uranium(IV) and iron(II) with a stopped-flow inductive kinetic spectrophotometric method

A kinetic method for simultaneous determination of multielements is proposed, and a procedure for simultaneous determination of uranium(VI) and iron(II) is established based on their inductive effect on the chromium(VI)-iodide redox reaction in weak acidic medium. The reaction was monitored with the stopped-flow spectrophotometric technique by using I ₃ ^– -starch complex as indicator. The calibration graphs are linear for 0–3.6 g.cm^–3 U(IV), and 0–2.5 g.cm^–3 Fe(II), respectively. Most foreign ions, except for V(IV), Sb(III), do not interfere with the determination.     

A kinetic determination of ultramicro quantities of manganese(II), molybdenum(VI) and tungsten(VI) on the basis of their catalytic action on the oxidation of Azorubin S by hydrogen peroxide

Summary A study has been made of the kinetics of catalytic oxidation of Azorubin S by hydrogen peroxide in the presence of Mn(II), Mo(VI) and W(VI) in order to find optimal conditions for the kinetic catalytic determination of these elements. Manganese(II), molybdenum(VI) and tungsten(VI) were determined in the concentration ranges 5.5–33.0×10^–3, 1.3–8.1 and 5.9–44.1g/ml, respectively. Standard deviations were less than 11%. The effect of some foreign ions on these determinations was also investigated.

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Zusammenfassung Die Kinetik der katalytischen Oxydation von Azorubin S mit Wasserstoffperoxid in Anwesenheit von Mn(II), Mo(VI) und W(VI) wurde untersucht, um die optimalen Bedingungen für deren kinetisch-katalytische Bestimmung zu finden. Mn(II) wurde im Konzentrationsbereich von 5,5–33,0×10^–3, Mo(VI) von 1,3–8,1 und W(VI) von 5,9–44,1g/ml mit Standardabweichungen <11% bestimmt. Außerdem wurden einige der möglichen Störungen untersucht.

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This work was presented in part at the 20th Annual Meeting of the Serbian Chemical Society, Belgrade, January 17, 1977.     

Spectrophotometric determination of molybdenum by extraction of its thiosulphate complex

A simple and rapid spectrophotometric determination of molybdenum is described. The molybdenum thiosulphate complex is extracted into isoamyl alcohol from 1·0–1·5M hydrochloric acid containing 36–40 mg of Na₂S₂O₃·5H₂O per ml. The absorbance at λ_max = 475 nm obeys Beer's law over the range 0–32 μg of Mo per ml of solvent phase. Up to 5 mg/ml of Ti(IV), V(V), Cr(VI), Fe(III), Co(II), Ni(II), U(VI), W(VI), Sb(III), 1 mg/ml of Cu(II), Sn(II), Bi(V) and 10 μg/ml of Pt(IV) and Pd(II) do not interfere. Large amounts of complexing agents interfere. The method has been applied to analysis of synthetic and industrial samples.     

Determination of99Tc-DPD complex composition and valence states of technetium

DPD (2,3-dicarboxypropane-1,1-diphosphonic acid) forms two complexes with⁹⁹Tc, previously reduced by Sn(II): with _max at 410 nm (pH 3–7), and at 515 nm (pH 5–9.6). By Job's method, formation of complexes with DPD:Tc molar ratios of 21 and 23 was found in acidic medium (pH=3). In order to determine the valence states of Tc in the complex, taking into account that formation of⁹⁹Tc-DPD complex does not occur in absence of a reducing agent (here divalent tin), the redox potentiometric titration method was applied. In acidic medium (pH=3), Tc was reduced to Tc(III) by Sn(II), while in presence of DPD to Tc(IV). In strongly alkaline medium (pH>13) the situation was reverse: Tc(III) was formed in the DPD complex, while Tc(IV) in absence of the ligand. In slightly alkaline medium (pH about 8) in both cases (with or without the ligand) TC(III) was obtained at the titration end point. This phenomenon can explain the dependence of^99mTc-radiopharmaceutical complexes on the sequence of reagent addition. These conclusions are very important for^99mTc-DPD radiopharmaceutical solutions used in diagnostic nuclear medicine for skeletal imaging.