A new liquid membrane electrode for the selective determination of perrhenate

A new perrhenate ion-selective electrode has been developed, incorporating a nitrobenzene solution of nitron perrhenate as a liquid membrane. The electrode gives near-Nernstian response to 3 x 10(-5)-10(-2)M perrhenate over the pH range 3-8. Most common anions (except for periodate and perchlorate) give little interference. The electrode has been satisfactory for direct potentiometric determination of as little as 10 mu/ml rhenium. The average recovery and standard deviation were 99% and 2.1%, respectively. Measurements of the solubility products of some sparingly soluble perrhenates gave results that agreed closely with those recorded in the literature and obtained by other procedures.     

Determination of rhenium in gold-containing ores by X-ray fluorescence spectrometry

A procedure is developed for determining rhenium in gold-containing ores by X-ray fluorescence spectrometry. The adsorption preconcentration of perrhenate ions on activated charcoal is studied. It is found that the pH of the solution, the time of exposing the adsorbent to the solution, UV irradiation, and the presence of associate elements (tungsten, gold, silver, and copper) affect the adsorption. The procedure is applied to the X-ray fluorescence determination of rhenium in gold-containing ores from different deposits.     

A new catalytic reaction of rhenium and its analytical application

Small amounts of perrhenate in fairly concentrated sulphuric acid media and in the presence of tin(II) chloride are found to catalyse the acid hydrolysis of alpha-furildioxime, with production of a new absorption peak at 320 nm, due to the di-alpha-furildiketone produced. The catalytically active species is a sulphate complex of rhenium(IV). The catalytic action of rhenium is promoted by citric acid. Rhenium can be determined in the range 0.0005-0.5 mug/ml. Interferences are eliminated by a preliminary extraction. The method has been applied to the determination of rhenium in copper concentrates of low rhenium content, copper ores and rocks. On the basis of the inhibitory effect of molybdenum the reaction can be used for determination of this element as well.     

In Process Citation

The sample (< 1 mg) is burnt in an oxygen flask for the determination of rhenium. It is destroyed by a wet process in a Kjeldahl flask for the determination of rhodium or tellurium (sample <4-5 mg) or zirconium (sample <1.5 mg). These elements are determined spectrophotometrically. The following reactions are used: reduction of perrhenate by tin(II) chloride in the presence of 2,2'-furildioxime or thiourea, complexation of rhodium(III) by sodium hypochlorite, formation of iodotellurite, complexation of zirconium(IV) with Xylenol Orange.     

Neutron activation analysis of rhenium in rocks and sediments by extraction chromatography on a pyridine-Kel-F column

A simple method for the determination of rhenium in rocks and sediments has been established. After a neutron-irradiated sample was decomposed by NaOH−Na₂O₂ fusion, the alkaline solution was fed onto a column of the mixed solvent pyridine-benzene (7:3 v/v) supported on Kel-F powder. By passage through the column of 4, 5N NaOH solution which had been equilibrated with the solvent mixture, perrhenate ion remained on the column but other nuclides were eluted. Subsequently, the perrhenate ion on the column could be eluted with a small amount of distilled water, and precipitated as tetraphenylarsonium perrhenate for counting the γ-activity of¹⁸⁶Re. By the present method 0.1 ng of rhenium could be determined with a recovery of 90–95% and an error of ±10%. A part of this work was performed at the Research Reactor Institute, Kyoto University.     

Gravimetric determination of rhenium as 2,4,6-triphenylpyrylium perrhenate

A gravimetric method for determination of rhenium is based on formation of sparingly soluble 2,4,6-triphenylpyrylium perrhenate. The conditional solubility product in O.1N sulphuric acid medium was found to be (3.72 +/- 0.08) x 10(-9). The interference of foreign anions (simple or complex) is eliminated by preliminary extraction of perrhenate with acetone from strongly alkaline medium. The method is applied to the determination of rhenium in perrhenates and rhenium alloys.     

The Study of Various Rhenium Compounds by Capillary Electrophoresis

The conditions for the synthesis of rhenium compounds (pH, reaction time, concentration of reducing agent) have been determined previously by thin-layer chromatography. A Britton-Robinson buffer solution has been selected as a carrier electrolyte due to its possible use in a wide interval of pH, mainly at optimal pH for the formation of the complexes studied. The same electrolyte has been previously applied also in case of the study of rhenium and technetium complexes by polarography. The electrophoretic experiments have been carried out under both standard and reverse polarities with direct UV detection at the wavelength 214 nm and 20 °C. The signal of perrhenate has been observed at the reverse polarity (outlet+, inlet–), of reduced rhenium [probably Re(IV)] under normal polarity. The formation of rhenium complexes with EDTA has been shown by lowering of the cationic rhenium signal due to the addition of the ligand. The rhenium complexes with EDTA are observable at reverse mode of CE. The formation of rhenium complexes with HEDP (hydroxyethylidenediphosphonic acid) has been studied in two different carrier electrolytes — 40 mM Britton-Robinson buffer solution and 50 mM phosphate buffer with 20 mM HEDP. The mechanism of perrhenate reduction by stannous chloride and of the formation of rhenium complexes with EDTA has been determined. The necessity of the presence of ascorbic acid as an antioxidant in the reaction mixture at different pH values has been described as well.     

Photoelectron Spectroscopy (XPS) and Thermogravimetry (TG) of Pure and Supported Rhenium Oxides. 2. Rhenium Oxides on Titanium Dioxide

Ammonium perrhenate supported on titanium dioxide has been investigated in order to elucidate the interaction between the carrier and the dispersed species. The samples, containing up to 14% by weight of rhenium, have been prepared by impregnation with an ammonium perrhenate solution. The study, performed using X-ray photoelectron spectroscopy and thermogravimetric techniques, demonstrates that a different situation is present depending on the starting rhenium content and gas environment. At low rhenium content (0–2.5%), rhenium is mainly atomically dispersed as per-rhenate-like surface compound; on heating in H₂ up to 500°C, the surface compound is reduced to metal which is still in a dispersed form. In the range 2.5–10% in addition to the perrhenate-like surface compound, small crystallites of NH₄ReO₄ are initially present on the surface. During the heat treatment in hydrogen these crystallites are reduced to ReO₂. The incorporation of Re(IV) in the TiO₂ structure preserves it from further reduction. At higher rhenium content large crystallites of ammonium perrhenate are present on the titanium dioxide surface. They show the reduction behaviour expected for this compound. The data also indicate that when metallic rhenium is heated in air, the heptoxide formed reacts with the free surface of the support and is not lost by volatilization.     

Chromatographic and electromigration analysis of rhenium compounds used in radiopharmacy

A large group of radiopharmaceuticals includes complex radionuclide-ligand compounds which are very sensitive to the preparation conditions, as for example pH of reaction mixture, incubation time, temperature, molar ratio of reagents, etc. It is necessary to find the optimum condition for the formation of the radionuclide-ligand complex and to select the convenient analytical methods to determine the purity of the product. The preparation of radiopharmaceuticals labeled by rhenium-186 or rhenium-188 requires the addition of a reducing agent (commonly stannous chloride) to the reaction mixture in order to reduce perrhenate to a lower oxidation state which is capable of complex formation. For rhenium concentration up to approximately 10^-5 mol/l, the molar excess of reduction agent over perrhenate is usually higher than 800 to reach the optimum yield of reduction and complexation (between 80-95%). Because of the potentially toxic effect of SnCl₂ the reduction of perrhenate by stannous chloride was studied in detail to find the way for decreasing the concentration of reducing agent in the reaction mixture without significant lowering of the yield of perrhenate reduction. The reduction of perrhenate was determined by electromigration methods, i.e., capillary electrophoresis (CZE) and isotachophoresis (ITP), and thin-layer chromatography (TLC) with radiometric detection. The highest degree of reduction of perrhenate was obtained at pH 2 at perrhenate concentration ranging from 10^-4 to 10^-3 mol/l. The stability of reduced rhenium against a pH change from 2 to 5.5 (which corresponds to the pH close to physiological values) was tested as well. The influence of the presence of ascorbic acid as an antioxidant in the reaction mixture on the stability of the preparation against the pH change was determined. The stability of reduced rhenium against dilution of rhenium in the reaction mixture to the concentration suitable for the application in radiotherapy was also found out. The data acquired by capillary electrophoresis, isotachophoresis and thin-layer chromatography are comparable. Results obtained in these experiments were applied for the study of rhenium complexes with hydroxyethylidenediphosphonic acid (HEDP).     

Extraction et dosage de traces de rhénium,en particulier dans les molybdénites

A simple solution to the difficult problem of the separation and determination of traces of rhenium contained in molybdenites is suggested. After the preliminary attack of the cres, rhenium is extracted quantitatively between, pH 8 and pH 9 by chloroform in the form of tetraphenylarsonium perrhenate. In this pH region the molybdenum remains in the aqueous phase.Calculation has allowed the determination of favourable conditions for the extraction of perrhenates by tetraphenylarsonium chloride and chloroform. Practical results are in satisfactory agreement with theory.The extracted rhenium, after conversion to the ions ReO₄^- in acid solution, is determined colorimetrically by reaction with thiocyanate and stannous chloride.By applying the method described it is possible to isolate and determine rhenium in molybdenites when the weight ratio rhenium/ore ecxeeds 10^-7.     

Chromatographic study of186Re complexes with various ligands

Thin-layer and paper chromatography have been used for the determination of radiochemical yields of¹⁸⁶Re complexation with three selected ligands methylenediphosphonic acid (MDP), ethylenediamminotetraacetic acid (EDTA), and citrate convenient for the radiopharmaceutical applications. The combination of selected two chromatographic systems has been chosen due to the satisfactory separation of free perrhenate, corresponding complex with¹⁸⁶Re and reduced hydrolyzed rhenium. Rhenium complexes with studied ligands were prepared by reduction of perrhenate at presence of suitable ligand. Stannous chloride together with ascorbic acid (antioxidant) was used for perrhenate reduction. The effect of pH of reaction mixture, reaction time and concentration of reducing agent on the radiochemical yield of complexation is described and the optimal conditions for synthesis of rhenium complexes with MDP, EDTA and citrate have been found. Under optimal condition the radiochemical yield of complexation¹⁸⁶Re-MDP,¹⁸⁶Re-EDTA and¹⁸⁶Re-citrate reached more than 90%, 80%, and 80%, respectively.     

Recovery of perrhenate ions with a macrocellular anion exchanger based on epoxidized monoethanolamine vinyl ether, allyl glycidyl ether, and polyethyleneimine

Sorption of perrhenate ions by a new anion exchanger based on epoxidized monoethanolamine vinyl ether, allyl glycidyl ether, and polyethyleneimine was studied. It was found that the anion exchanger has a high sorption capacity for rhenium ions.     

Radiochemical separation of rhenium with crown ether for neutron activation analysis in rocks

The extraction behavior of perrhenate with crown ethers has been studied and methods for the separation and determination of rhenium have been developed. Perrhenate anion can be quantitatively extracted into nitrobenzene by benzo-15-crown-5 (B15C5) from 2M potassium hydroxide and back-extracted by sodium phosphate buffer solution. The molar ratio of B15C5 to KReO₄ in the extracted species is probably 21. Rhenium was satisfactorily determined by neutron activation method in rock samples.     

Applications of inductively coupled plasma mass spectrometry and laser ablation inductively coupled plasma mass spectrometry in materials science

Inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS (LA-ICP-MS) have been applied as the most important inorganic mass spectrometric techniques having multielemental capability for the characterization of solid samples in materials science. ICP-MS is used for the sensitive determination of trace and ultratrace elements in digested solutions of solid samples or of process chemicals (ultrapure water, acids and organic solutions) for the semiconductor industry with detection limits down to sub-picogram per liter levels. Whereas ICP-MS on solid samples (e.g. high-purity ceramics) sometimes requires time-consuming sample preparation for its application in materials science, and the risk of contamination is a serious drawback, a fast, direct determination of trace elements in solid materials without any sample preparation by LA-ICP-MS is possible. The detection limits for the direct analysis of solid samples by LA-ICP-MS have been determined for many elements down to the nanogram per gram range. A deterioration of detection limits was observed for elements where interferences with polyatomic ions occur. The inherent interference problem can often be solved by applying a double-focusing sector field mass spectrometer at higher mass resolution or by collision-induced reactions of polyatomic ions with a collision gas using an ICP-MS fitted with collision cell. The main problem of LA-ICP-MS is quantification if no suitable standard reference materials with a similar matrix composition are available. The calibration problem in LA-ICP-MS can be solved using on-line solution-based calibration, and different procedures, such as external calibration and standard addition, have been discussed with respect to their application in materials science. The application of isotope dilution in solution-based calibration for trace metal determination in small amounts of noble metals has been developed as a new calibration strategy. This review discusses new analytical developments and possible applications of ICP-MS and LA-ICP-MS for the quantitative determination of trace elements and in surface analysis for materials science.     

氧化镁烧结-电感耦合等离子质谱法测定冰铜中的铼

本文建立了一种利用电感耦合等离子体质谱法（ICP-MS）测定冰铜中铼的方法。样品经氧化镁烧结,热水浸取法处理,溶液经732强酸型阳离子交换树脂处理交换去除干扰离子,实现了ICP-MS直接测定冰铜中的铼。实验结果表明,在最佳试验条件下,方法的检出限可低至0.010mg/t,加标回收率为92.00%~104.00%,测定结果的相对标准偏差（RSD,n=7）小于5%,测定结果令人满意。由此可见,该方法精密度高,准确度高,可用于冰铜中铼的测定。     

Electrochemical behavior of aqueous acid perrhenate-containing solutions on noble metals: critical review and new experimental evidence

The actual state of the art in the reduction of perrhenate ions on noble metals is reviewed and discussed. Also, with the aim of contributing to better knowledge of this process, results of several experiments are presented. For the first time, spectroscopic evidence on the nature of the deposited rhenium layer on Pt and Rh and the detection of an intermediate in the reduction pathway toward metallic rhenium is provided. The role of the substrate in the electroreduction of perrhenate ions in aqueous acid media is emphasized, because it is directly associated with the formation of different H-containing species as reducing agents. Thus, those metals capable of adsorbing H atoms are able to reduce ReO(4)(-) to ReO(2) by H(ad) at potentials more positive than that of the hydrogen evolution reaction. Moreover, H(ad) reacts with the ReO(2) layer previously deposited, resulting in the formation of Re(III)-soluble species, which subsequently undergo disproportionation to Re and ReO(2). For metals that are not capable of adsorbing H, i.e., Au, molecular hydrogen is the reducing agent, leading to the formation of metallic Re. In addition, ReO(4)(-) is chemically reduced to metallic Re by hydride.     

Separation of rhenium by extraction with crown ethers and flow-injection extraction—spectrophotometric determination with Brilliant Green

The extraction behavior of perrhenate with crown ethers was studied and methods for the separation and determination of rhenium were developed. The distribution ratio of perrhenate with dicyclohexano-18-crown-6 (DC18C6) increases with increases in the dielectric constant of organic solvents and in the potassium ion concentration of aqueous solution. The molar ratios of crown ether to KReO₄ in the extracted species are probably 1:1 for DC18C6, dibenzo-18-crown-6 and 18-crown-6 and 2:1 for benzo-15-crown-5 and 15-crown-5. Microgram amounts of rhenium were satisfactorily separated from large amounts of molbdenum(VI) by extraction with DC18C6 in 1,2-dichloroethane from 2 M potassium hydroxide solution containing tartrate and by back-extraction with sodium phosphate buffer solution after the addition of a twofold volume of hexane to the organic phase. Rhenium was determined by the flow-injection extraction-photometric method with Brilliant Green. Rhenium was satisfactory determined in molybdenite and other ore samples.     

Multielemental characterisation of cobalt by glow discharge quadrupole mass spectrometry

Multielemental determination and the assessment of purity of cobalt metal used in the preparation of Ni-based super-alloys have been carried out by glow discharge quadrupole mass spectrometry (GD-QMS). Relative sensitivity factors (RSF) generated from certified iron matrix reference samples (NIST 663 and 664 low alloy steel pin standards) could be used for the determination of different trace element constituents of the sample. Different wet chemical procedures were also carried out for the determination of the trace constituents in the sample. The GD-QMS results are in reasonably good agreement with those obtained from wet chemical procedures, validating the use of the RSF values generated on low alloy steel standards for the computation of trace element concentrations in cobalt metal. A variety of molecular ions formed through the reaction of cobalt (matrix) with the discharge gas (argon) were also detected.     

Study of perrhenate reduction by capillary electrophoresis

The influence of perrhenate concentration, the concentration of the reducing agent and pH of the reaction mixture on the yield of perrhenate reduction were studied to find a possibility to decrease the stannous chloride concentration in the reaction mixture without negative changes on the yield of perrhenate reduction. Britton-Robinson buffer solutions were selected as the background electrolytes because of their buffering capacity in a wide pH interval. The highest degree of perrhenate reduction was obtained at pH 2 at perrhenate concentrations ranging from 10(-4) to 10(-3) mol/L. The stability of reduced rhenium against pH change from 2 to 5.5 and against dilution of rhenium in the reaction mixture to the concentration suitable for the application in radiotherapy were studied as well. The results obtained by capillary electrophoresis and by thin-layer chromatography with radiometric detection were compared.     

Determination of rhenium in the URe2 binary compound by differential spectrophotometry

A differential spectrophotometric determination of rhenium in its binary compound with uranium is described; the method is based on the action of tin(II) chloride on perrhenate in the presence of dimethylglyoxime with measurement at 445 nm. Uranium does not interfere. For solutions containing about 1 mg of rhenium, the coefficient of variation was 0.08%.