Separation of rhenium(vii) from molybdenum(vi) and many other elements by anion exchange

A method is described for the selective separation of μg and mg amounts of rhenium(VII) from molybdenum (VI) and many other metal ions by means of the strongly basic anion-exchange resin Dowex 1-X8. The separation is based on the preferential elution of molybdenum by a 90% (v/v) methanol-10% 6 M nitric acid mixture; rhenium and a few other elements are retained while molybdenum and most other metal ions including Fe(III), Ca, Mg, Mn, U, Cu, V, etc., are practically unadsorbed. After elution of the adsorbed rhenium with 70% (v/v) tetrahydrofuran-30% 9 M hydrochloric acid, the rhenium is determined spectrophotometrically by a modified thiocyanate method.     

Neutron activation of traces in electrolytic zinc sulphate solutions : Simultaneous determination of mercury,uranium and ytterbium

A neutron activation determination of traces of mercury, uranium and ytterblum in electrolytic zinc sulphate solutions has been devised The isotope ¹⁹⁷Hg was measured by means of its 68-and 77-keV photopeaks Uranium was determined by measurements of the 106-keV photopeak of the ²³⁹Np daughter activity The 50- and 53-keV X-rays of ytterbium isotopes ¹⁹⁹Yb and ¹⁷⁵Yb were counted using a 1-mm thick Nal(Tl) wafer crystal The chemical separation was performed on anion-exchange resin. The matrix activities were eliminated in 185N hydrofluoric acid while the neptunium and ytterbium activities were desorbed with 5N hydrochloric acid Mercury was eluted from the column with 0.5 M thourea-0.005 N hydrochloric acid and precipitated as sulpinde     

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.     

Determination of rhenium in molybdenites by neutron activation analysis

A thermal neutron activation method for the determination of rhenium in molybdenites is described. The rhenium is separated from the matrix after irradiation by pyridine extraction from 4 N sodium hydroxide solution; γ- and β-spectrometry are applicable. For a neutron flux of 4 · 10¹¹ n/cm².sec, an irradiation of 2 h and a sample of ca. 50 mg, β-counting allows determinations in the p.p.b. range.     

Flow-injection catalytic spectrophotometic determination of molybdenum(VI) in plants using bromate oxidative coupling of p-hydrazinobensenesulfonic acid with N-(1-naphthyl)ethylenediamine

A novel flow-injection spectrophotometry has been developed for the determination of molybdenum(VI) at nanograms per milliliter levels. The method is based on the catalytic effect of molybdenum(VI) on the bromate oxidative coupling of p-hydrazinobenzenesulfonic acid with N-(1-naphthyl)ethylenediamine to form an azo dye (λ_max = 530 nm). Chromotropic acid (4,5-dihydroxy-2,7-naphthalenedisulfonic acid) acted as an effective activator for the molybdenum(VI)-catalyzed reaction and increased the sensitivity of the method. The reaction was monitored by measuring the change in absorbance of the dye produced. The proposed method allowed the determination of molybdenum(VI) in the range 1.0-20 ng mL⁻¹ with sample throughput of 15 h⁻¹. The limit of detection was 0.5 ng mL⁻¹ and a relative standard deviation for 10 ng mL⁻¹ molybdenum(VI) (n = 10) was 2.5%. The interfering ions were eliminated by using the combination of a masking agent and on-line minicolumn packed with cation exchanger. The present method was successfully applied to the determination of molybdenum(VI) in plant foodstuffs.     

Spectrophotometric Determination of Rhenium(IV) with Thiocyanate,TX-100 and N,N′-Diphenylbenzamidine

A spectrophotometric method to determine rhenium(IV) at trace level is based on the extraction of Re(IV)-SCN^? complex in sulphuric acid media with N,N′-diphenylbenzamidine(DPBA) in presence of a non-ionic surfactant triton X-100 (TX-100) in chloroform. The complex shows maximum absorbance at 435 nm with amolar absorptivity value of 4.24 × 10⁴ L mol^?1 cm^?1 at an acidity range 3.5-6.5 M H₂SO₄. The method followed Beer's Law for the system Re(IV)-SCN^?(TX-100)-DPBA upto 4.0 μg Re(IV) mL^?1. The detection limit of the method is 5 ppb. None of the tested foreign ions, except molybdenum(VI), interfere with the determination of rhenium. The interference due to molybdenum could effectively be removed by prior precipitation with oxine. The effect of various analytical parameters on the extraction of the metal are discussed.     

Methods for the separation of rhenium, osmium and molybdenum applicable to isotope geochemistry

Effective methods are described for the chemical separation of rhenium, osmium and molybdenum. The methods are based on distillation and anion-exchange chromatography, and have been the basis for rhenium-osmium isotope studies of ore deposits and meteorites. Successful anion-exchange separation of osmium requires both recognition and careful control of the osmium species in solution; thus, distillation of osmium tetroxide from a mixture of sulfuric acid and hydrogen peroxide is preferred to anion-exchange. Distribution coefficients measured for perrhenate in sulfuric acid media are sufficiently high (K(d) > 500) for rhenium to be directly loaded onto an ion-exchange column from a distillation residue and subsequently eluted with nitric acid. Polymerization of molybdenum species during elution is prevented by use of a solution that is 1M in hydrochloric acid and 1M in sodium chloride.     

Separation of alkaline earth elements by cation-exchange chromatography in ammonium malonate media

Be(II), Mg(II), Ca(II), Sr(II) and Ba(II) can be separated by elution from a cation-exchange column in the ammonium form with increasing concentrations of ammonium malonate. A typical elution sequence for a 60-ml column (volume in H⁺-form) of AG₅₀-X8 resin is: 200 ml of 0.20 N ammonium malonate plus 0.10 N malonic acid for Be(II); 300 ml of 0.50 N, 450 ml of 0.70 N, 350 ml of 1.10 N ammonium malonate for Mg(II), Ca(II) and Sr(II), respectively, and 200 ml of 3.0 N nitric acid for Ba(II). Separations are sharp and quantitative for element pairs in weight ratios from 1:1000 to 1000:1. Distribution coefficients, elution curves and quantitative separations are presented.     

Molybdenum determination in iron matrices by ICP-AES after separation and preconcentration using polyurethane foam

A procedure is proposed for the separation and determination of molybdenum in iron matrices by a batch process. It is based on the solid-phase extraction of the molybdenum(V) ion as thiocyanate complex on polyurethane (PU) foam. The extraction parameters were optimized. Using 0.20 mol L^–1 hydrochloric acid, a thiocyanate concentration of 0.10 mol L^–1, 100 mg of polyurethane foam and shaking time of 10 min, molybdenum (5–400 μg) can be separated and preconcentrated from large amounts of iron (10 mg). Desorption was carried out instantaneously by conc. nitric acid or acetone. Distribution coefficients, sorption capacity of the PU foam and coefficients of variation were also evaluated. The effect of some ions on the separation procedure was assessed. Iron(III) should be reduced to iron(II). The proposed procedure was used to determine molybdenum in standard iron matrices such as steel and pure iron. The achieved results did not show significant differences with certified values.     

Rhenium(I) and technetium-99m(I) fac-tricarbonyl complexes with 4-(imidazolin-2-yl)-3-thiabutanoic acid derivatives as tridentate ligands: Synthesis and structural characterization

Two rhenium(I) tricarbonyl complexes, with the monoanionic tridentate NSO type ligand, 4-(imidazolin-2-yl)-3-thiabutanoic acid and 4-(N-ethylimidazolin-2-yl)-3-thiabutanoic acid were synthesized and isolated in pure form. Both complexes were characterized by spectroscopic methods and elemental analysis. The solid-state structure of 4-(imidazolin-2-yl)-3-thiabutanoic acid and of both complexes was established by X-ray crystallography. The geometry about the rhenium is octahedral. The analogous technetium-99m complexes were also prepared quantitatively by the reaction of both ligands with the fac-[^99mTc(CO)₃(H₂O)₃]⁺ synthon and their identity was established by chromatographic comparison to their rhenium congeners.     

Determination of five nucleosides by LC‐MS/MS and the application of the method to quantify N6‐methyladenosine level in liver messenger ribonucleic acid of an acetaminophen‐induced hepatotoxicity mouse model

Ribonucleic acid N⁶‐methyladenosine methylation plays an important role in a variety of biological processes and diseases. Acetaminophen‐induced hepatotoxicity is one of the major challenges faced by clinicians. To date, the link between N⁶‐methyladenosine and acetaminophen‐induced hepatotoxicity has not been studied. In this study, a simple ultra high performance liquid chromatography with tandem mass spectrometry method was developed for the simultaneous determination of five nucleosides (adenosine, uridine, cytidine, guanosine, and N⁶‐methyladenosine) in messenger ribonucleic acid. After enzymatic digestion of messenger ribonucleic acid, the nucleosides sample was separated on an Acquity UPLC column with gradient elution using methanol and 0.02% formic acid water, and detected by a Qtrap 4500 mass spectrometer with an electrospray ionization mode. The method was validated over the concentration ranges of 4–800 ng/mL for adenosine, uridine, cytidine, and guanosine and 0.1–20 ng/mL for N⁶‐methyladenosine. It was successfully applied to the determination of N⁶‐methyladenosine levels in liver messenger ribonucleic acid in an acetaminophen‐induced hepatotoxicity mouse model and a control group. This study offers a method for the determination of nucleoside contents in epigenetic studies and constitutes the first step toward the investigation of ribonucleic acid methylation in acetaminophen‐induced hepatotoxicity, which will facilitate the elucidation of its mechanism.     

Determination of molybdenum in biological materials by neutron activation

A method of the determination of molybdenum in biological materials by neutron activation is described. The method is based on the γ-spectrometric measurement of^99mTc after radiochemical separation of the latter by substoichiometric extraction with tetraphenylarsonium chloride using rhenium as inactive carrier. The method has been tested with reference materials.     

Determination of <Emphasis Type="Italic">N</Emphasis>-acetylneuraminic acid in poultry eggs by ultra performance liquid chromatography–tandem mass spectrometry

N-acetylneuraminic acid is an important member of sialic acids which is a family of nine-carbon carboxylated sugars most frequently found in terminal position in glycoconjugates. It was widely distributed in different portions of organisms. In this study, a method of ultra performance liquid chromatography–tandem mass spectrometry was developed for the determination of N-acetylneuraminic acid in poultry eggs. The N-acetylneuraminic acid was freed by heating the materials in 0.1 M H₂SO₄ at 80°C for 2 h. Then, chloroform reagent was used to eliminate phospholipids, cholesterol and other organic impurities, meanwhile, it was able to precipitate protein. In the cleanup step, C18 solid phase extraction columns were used to purify the matrix. Determination of N-acetylneuraminic acid was performed with electrospray ionization in negative ion mode. Chromatographic separation was performed on a Waters Acquity UPLC BEH C18 (100 × 2.1 mm, 1.7 μm) analytical column. The gradient elution reagent was acetonitrile and water (containing 0.1% formic acid). The tandem spectrometer was operated in the Multiple Reaction Monitoring mode. The linearity over of sialic acids on-column had a correlation coefficient greater than 0.999. The detection method of N-acetylneuraminic acid in the poultry eggs had good precision and acceptable recovery.     

Separation of iodine produced from fission with a porous metal silver column in99Mo production

In Argentina, at the Ezeiza Atomic Center,¹³¹I is produced by wet distillation of natural tellurium dioxide irradiated with thermal neutrons in a pool-type reactor. In order to recover the¹³¹I present in the production process of fission⁹⁹Mo obtained by irradiation of UAL_x/Al targets (with 90% enriched uranium) a separation method was developed. Iodine isotopes can be separated from a sodium hydroxide solution containing fission products using a column filled with alternate beds of glass microspheres and porous metal silver. Tests with tracers were performed in radiochemical laboratory. Following this results, a series of tests with higher activities (3 TBq of⁹⁹Mo and 0.7 TBq of¹³¹I) were carried out in hot cells. Molybdenum passes through the silver column, while¹³¹I retention was 92–97% in tracer test and 90% in optimised hot cell tests. This result depends on several facts that are discussed. An initial separation of iodine isotopes diminishes radiation damage on ion-exchange resin used in the subsequent molybdenum purification, improving its retention and elution yield.     

Separations involving sulphides : Separation of bismuth,cadmium and indium from various other elements that form thiosalts

It has been shown that 2N sodium sulphide reagent can be successfully used in separating tellurium, molybdenum, antimony or rhenium from bismuth., platinum, gold, selenium, rhenium, arsenic, molybdenum or tellurium from cadmium; platinum, gold, selenium, rhenium, arsenic, molybdenum, tellurium or antimony from indium.It is not possible to separate quantitatively arsenic, platinum, gold or selenium from bismuth; antimony from cadmium; and tin from bismuth, cadmium or indium.     

Anion-exchange separation of cadmium in organic solvent-nitric acid media

The anion-exchange separation of cadmium from zinc and aluminium in organic solvent-nitric acid mixtures was studied. The distribution coefficients of the 3 elements in various 90% organic solvcnt-10% 5 N nitric acid media were determined for Dowex I-X8 resin. A 90% ethanol-10% 5 N nitric acid medium was most satisfactory for the quantitative separation of cadmium from zinc and aluminium. The method was applied to the analysis of some copper and aluminium base alloys. Methyl glycol or acetic acid could be used instead of ethanol. Both cadmium and zinc were strongly adsorbed from a 90% propionc acid-10% 5 N nitric acid medium; separation was then effected by gradient elution.     

Ion exchange resins in steel analysis

The metals vanadium, chromium and molybdenum may be separated from the other constituents of steel by passing an acetate buffered solution of the steel through a strongly basic onion exchanger and selectively eluting the above metals from the resin column with aqueous solutions of 0.6 N sodium hydroxide, 8 N hydrochloric acid and 1 N hydrochloric acid, respectively.     

Chromatographic retention of molybdenum,titanium and uranium complexes for removal of some interference in inductively-coupled plasma mass spectrometry

Complexes of molybdenum(CI) or titanium(IV) with N-mehylfurohydroxamic acid (N-MFHA) are retained on a column packed with polystyrene/divinylbenzene. At the pH values chosen, copper , zinc and cadmium are washed rapidly through the column and are detected by inductively-coupled plasma mass spectrometry (i.c.p./m.s.) without interference from metal oxide ions of titanium or molybdenum. Detections limits are 1 to 2 μg 1^?1, and analyte recoveries are essentially 100%. the resin capacity for the titanium and molybdenum complexes is sufficient for several hundred injections and the complexes can be radily washed from the column. Uranium(IV) also forms a stable complex with N-MFHA, and ionizatin interference caused by excess of uranium can be avoided by chromatographic removal of the uranium complex. Various other potentially interfering elements with aqueous oxidations states of ⁺4 or higher (e.g., Sn, W, Hf or Zr) could also be separated by this technique.     

Recent advances of rhenium separation and enrichment in China: Industrial processes and laboratory trials

The recent progresses in the separation and enrichment of rhenium were reviewed in this paper, especially, the advances in China.