Chemical separation of molybdenum from uranium and fission product nuclides

A very rapid method for the separation of molybdenum(VI) from neutron irradiated uranium and its fission products is described. The procedure is based on the selective extraction of molybdenum(VI) by a 0.1M solution of 2-hexylpyridine in benzene from 4M HCl+0.04M KSCN. Decontamination factors were estimated to be >10⁴ for the radionuclides of niobium, zirconium, ruthenium, lanthanum, cerium, promethium, yttrium, strontium and barium.     

On the mechanism of trivalent actinide extraction in the system HDEHP—Lactic acid with DTPA

The dependence of the distribution coefficients on the hydrogen ion concentration and HDEHP concentration in the process of extraction from lactic acid solutions in the presence of DTPA and without it has been investigated. It has been shown that when the lactate ion concentration is higher than 0.01M, Cm is extracted predominantly as the first lactate complex. The presence of DTPA does not change the extraction mechanism. Similarity of the observed regularities for trivalent actinides and lanthanides is confirmed by the extraction of Bk(III), Ce(III), and Eu(III). It is suggested that the nature of carbonic acid used in TALSPEAK-process greatly influences the efficiency of group separation of TPE and lanthanides. It is supported by some experimental data. The extraction and stability constants of the first lactate complex (Cm Lact²⁺) have been found to be: K_e=2, β ₁ ⁰ = 7,7 · 10³. In the practical lactic acid concentration range (1 M) the unextractable complex, Cm Lact₃, is also formed in the aqueous phase. The stability constant of this complex has been found to be β ₃ ⁰ = 1.2 · 10⁷.     

Tracer scale solvent extraction separation of tantalum from niobium using di-(2-ethylhexyl)-phosphoric acid as extractant

A simple solvent extraction procedure for the efficient separation of the radioactive tracers⁹⁵Nb and¹⁸²Ta from each other in a mixture using di-(2-ethylhexyl)phosphoric acid (HDEHP) as extractant is described. Tantalum was found to be quantitatively extracted from an aqueous madium, which is 1.6N in HCl and 10^?2 M in oxalic acid, with a HDEHP solution of 0.1 M concentration. Extractabilities of both niobium and tantalum in mineral acids like HCl, H₂SO₄ and HNO₃ and in some organic acids like oxalic, citric, etc., in HDEHP under the experimental conditions were also studied. The reliability of the separation procedure was verified further by γ-ray spectrometry.     

The impact of immobilized metal affinity chromatography (IMAC) resins on DNA aptamer selection

DNA aptamers are single-stranded oligonucleotides which can form various secondary and tertiary structures. They can recognize a broad range of targets ranging from small molecules, such as ions, vitamins, antibiotics, to high molecular weight structures, including enzymes and antibodies. DNA aptamers are extensively studied as a potential source of new pharmaceutical drugs due to their inexpensive synthesis, low immunogenicity, and high specificity. The commonly used aptamer selection procedure is systematic evolution of ligands by exponential enrichment (SELEX) where the target molecule is immobilized on an appropriate chromatography resin. For peptide/protein targets, immobilized metal affinity chromatography (IMAC) resins are frequently used. There is a broad range of commercially available resins which can be used for IMAC. They are characterized by different metal ions, linker types, and bead materials. In this study, we tested the impact of different IMAC resins on the DNA aptamer selection process during eight SELEX cycles. A histidine-tagged 29 amino acid peptide corresponding to the interdomain connecting loop of human proliferating cell nuclear antigen was used as a selection target. Different resin materials containing the same metal ion (Co²⁺) were tested. Simultaneously, agarose resins containing identical linkers, but different metal ions (Co²⁺, Cu²⁺, Ni²⁺, and Zn²⁺) were analyzed. The results of this study clearly demonstrated the impact of the metal ion and resin material on the DNA aptamer selection progress. The presented data indicate that for successful IMAC resin-based SELEX, the determination of the optimal resin might be crucial.     

Behavior of fatty acid during the incubation of bovine serum albumin. Entity of the serum albumin resistant to heat

The solution of bovine serum albumin, incubated at pH 9 (0.1 M Tris-EDTA-boric acid buffer in which 0.15 M KCl was contained) and 65 °C for 60 min, gave zones of undenatured monomer (component 1) and aggregates in the pattern of gel electrophoresis. The component 1, isolated from this solution, contained more fatty acids than the original albumin and than the mixture of aggregates. The aggregates contained substantially no fatty acids. This means that fatty acids are released, when the bovine albumin is denatured accompanying with intra- and intermolecular SH/S-S exchange reactions. Taking palmitic acid as a representative of the long chain fatty acid, a model experiment was performed. The bovine albumin, to which 6 palmitic acids were bound, did not cause the SH/S-S exchange reaction and was not denatured on incubation at pH 9 (0.1 M Tris-EDTA-boric acid buffer) and 65 °C. When the solution of “crystalline bovine albumin” (AF_0.9, A: albumin, F: long chain fatty acid) was incubated at pH 9 (0.1 M Tris-EDTA-boric acid buffer) and 65 °C, 20% of the albumin was not denatured even after prolonged incubation. Further, when the component 1 (AF_3.8), isolated from pre-incubated albumin solution, was incubated again at pH 9 and 65 °C, 58% of the albumin was not denatured even after sufficient time of incubation. Quantitative analysis reveals that the bovine albumin containing 6 fatty acids (AF₆) is not denatured at all, and is the entity of the albumin resistant to heat.     

Plutonium-244 dating

Re-examination of all known xenon isotopic data for ordinary chondrites reveals that²⁴⁴Pu fission xenon can be resolved in about one-fourth of the meteorites of this class. The amounts of²⁴⁴Pu fission xenon found in these meteorites range from ca. 1–2 up to 6–8·10^?12 ccSTP/g. These meteorites started to retain their xenon some 200–500 million years later than did the carbonaceous chondrites Allende, Groznaya, Mokoia, Murchison, Murray, and Renazzo which began to retain their xenon over 4800 million years ago.     

The effects of reaction conditions on porous chelating polymers designed for the decontamination of nuclear waste

The effect of a number of synthetic variables on the affinities of resorcinol-formaldehyde-iminodiacetic acid resins for¹³⁷Cs and⁹⁰Sr was determined. Porosity was introduced into the resins by inclusion of CaCO₃ as a solid template during the synthesis. Among the variables examined were reaction temperature, reactant ratio, choice of basic catalyst, and amount of added template. Only reaction temperature was found to have a clearly defined influence on affinity. Cesium-137 affinity increased with increasing reaction temperature. Affinity for⁹⁰Sr was independent of reaction temperature below reflux temperature, but dropped drastically for resins synthesized at reflux. These results are explained mechanistically. The reproducibility of the resin synthesis is also examined.     

Experimental Design Approach for Selective Separation of Vilazodone HCl and Its Degradants by LC-PDA and Characterization of Major Degradants by LC/QTOF–MS/MS

A selective, rapid, accurate and precise stability-indicating RP-HPLC method was developed for monitoring vilazodone in the presence of its degradation products (DPs) in API and pharmaceutical dosages. Chromatographic separation was achieved using a Grace phenyl C₁₈ column (250 × 4.6 mm, 5 µm particle size) at a flow rate of 1.0 mL min^?1 with a linear gradient elution of ammonium acetate buffer (10 mM, pH 5.0 adjusted by acetic acid) with acetonitrile as the mobile phase. Detection was performed at 240 nm. The chromatographic conditions were optimized by the design of experiments to obtain the best possible separation with a minimum number of trials. A face-centered central composite design (three levels for each factor) was employed for optimization, and an interaction of the independent variables (pH of mobile phase, column temperature and  % of organic modifier) on the resolution of critical pairs was studied. The drug was subjected to the stress conditions of hydrolytic (acid, base and neutral), oxidative, thermal and photolytic degradation. It was found to be degraded significantly in hydrolytic (basic and acid) and oxidative conditions, while it was stable in neutral hydrolytic, thermal and photolytic conditions. LC-QTOF/MS/MS studies were carried out to characterize the major DPs. The method was fully validated for selectivity, linearity, accuracy, precision and robustness in compliance with ICH guideline Q2 (R1).     

Determination of traces of uranium in tungsten and molybdenum by radiochemical neutron activation analysis via the fission product140Ba

A radiochemical separation procedure has been developed to determine traces of uranium in tungsten and molybdenum. In this procedure the fission product¹⁴⁰Ba, as indicator nuclide for uranium, is selectively separated from the matrix activities and from all other long-lived activation and fission products and obtained at high purity. The radionuclide in the final fraction is sufficiently pure so that it can be measured with high counting efficiency by -counting. The separation procedure consists of two steps: a cation-exchange separation to separate barium from the anionic matrix tungste or molybdate, and many other elements. In the second step the Ba-fraction is further purified by precipitation of barium as barium chloride in 8M hydrochloric acid. The precipitate is then dissolved in water for -counting via the Cerenkov effect. The chemical yield for barium is 94.6±2.6%. When samples of 0.1 g, a thermal neutron flux of 2·10¹³ n·cm^–2·s^–1, an irradiation time of 10 hours and a measuring time of 2 hours were applied, then the detection limit of uranium was 4 ng/g.Presented at the 3rd Intern. Conf. on Nuclear and Radiochemistry, Vienna, September 7–11, 1992.     

Extraction of Ag(I), Cd(II), In(III), Sn(II), Sn(IV), Sb(III), and U(VI) from aqueous solutions by ketone solutions using single-step batch and continuous SISAK methods1,2

The extraction properties of Ag(I), Cd(II), In(III), Sn(II), Sn(IV), Sb(III), and U(VI) from aqueous KI/H₂SO₄ solution into a mixture of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK) and cyclohexanone (CHO) were studied. Both single-step batch and SISAK² methods were used. The oxidation of Sn(II) to Sn(IV) by iodine and complexation of Sn(IV) by 2,3-dimercapto-propanol-1 (BAL) were also investigated. A method for rapid and continuous separation of indium from tin was developed for investigation of short-lived indium fission products.     

Simple and rapid methods for labelling of human IgG by four radionuclides

Labelling of DTPA bicyclic anhydride coupled antibodies were investigated by determining the effect of DTPA: antibodies, DTPA: Sn molar ratios, pH, dimer and polymer formation of antibodies coupled with DTPA, using three different radionuclides, [¹¹¹In,⁹⁰Y and^99mTc]. Analyses were performed with by Whatman No. 1 paper strips. Under optimal conditions we have achieved specific activities of¹¹¹In or⁹⁰Y labelled antibodies of about 37 kBq/1 g for IgG coupled with about 2 DTPA groups per molecule and protein concentration of 15 mg/ml.     

4-(5-nonyl)pyridine extraction of platinum from different aqueous solutions

The partition of tracer-level (<10^?7 mole/l) platinum between various 4-(5-nonyl)-pyridine phases and aqueous nitric, hydrochloric, and sulphuric acid phases has been studied radiometrically as a function of the amine and acid concentrations. The effects of saltingout agents and some anions on the extraction of the metal are reported. The extraction data is compared with that of gold and conditions are established for the separation of daughter¹⁹⁹Au from neutron irradiated platinum. The distribution coefficients of various metal ions are given for the 4-(5-nonyl)pyridine-10M HCl system and their factors for separation from platinum estimated.     

Extraction studies of trivalent ions from TALSPEAK medium using phsophonic acid-TBP solvent mixture

Indigenously synthesized extractant, phenyl (octyl) phosphonic acid (POPA) in tri-n-butylphosphate (TBP) and dodecane, has been investigated for the separation of americium from trivalent lanthanides in nitric acid medium as well as diethylene triaminepentaacetic acid (DTPA) and lactic acid mixture (TALSPEAK medium). Various experimental parameters like concentration of DTPA, lactic acid, TBP, nitrate ions and pH of the aqueous feed solution have been optimized to obtain the highest separation factor between americium and europium. Bulk actinide–lanthanide separation reagent, tetra (ethylhexyl) diglycolamide (TEHDGA), was equilibrated with simulated solution of americium and lanthanides, equivalent in concentration to the reprocessing waste originating from PHWR spent fuel. DTPA/lactic acid mixture was used to strip the metal ions from the loaded organic phase and re-extracted into POPA in TBP/dodecane to evaluate the separation factor of individual lanthanides with respect to americium. Very good separation factors between americium and trivalent lanthanides were obtained.     

Photo-induced disproportionation of iodomalonic acid

The stoichiometry, equilibrium, and kinetics of the photo-induced disproportionation of iodomalonic acid to I^?, I₂, and tartronic acid have been studied by means of spectrophotometry and iodide selective electrode at 20.0 ± 0.2°C, pH 2.0–4.0. At pH > 2.9, only I^? and HOCH(COOH)₂ are detected as major products and the reaction reaches 100% conversion. At pH < 2.9, I₂ and malonic acid are also formed and the reaction stops at a conversion rate less than 100%. Both UV (band with a peak at 360 nm) and visible light (480 nm) have been found to be effective. Two primary photochemical processes are identified: While both reactions are sensitive to UV light, only (M2) can be affected by visible light. (M1) and (M2) are considered to initiate a chain reaction sequence in which I^· radicals oxidize iodomalonic acid. Dual effects of reaction products on the reaction rate have been observed: while iodine increases the efficiency of visible light and accelerates the reaction, malonic acid inhibits the photo-decomposition by mediating the recombination of I^· radicals to I₂. © 1995 John Wiley & Sons, Inc.     

Cu-based atom transfer radical polymerization of methyl methacrylate using a novel tridentate ligand with mixed donor atoms

This study is aimed at atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) using a novel catalyst. The bis-(2-dodecylsulfanyl-ethyl)-amine (SNS) tridentate ligand with mixed donor atoms was synthesized in high purity using inexpensive reagents and was reacted with copper(I) bromide to produce the CuBr/SNS catalyst. The catalyst mediated living polymerization of MMA yielding polymers with controlled molecular masses and narrow molecular mass distributions (PDI < 1.25). Also, the kinetic plot exhibited a linear increase of ln([M]₀/[M]) versus time, indicating constant concentration of propagating radicals during the polymerization. The products were characterized by ¹H NMR, ¹³C NMR, FT-IR, UV-VIS, GC and elemental analyses (CHNS) and by GPC.     

Separation of methyltin species from inorganic tin,and their interactions with humates in natural waters

Tin(II) and tin(IV) are absorbed from aqueous solutions by Sephadex G-25 gel, from which they can be eluted by humates or fulvates, with which they interact more strongly. Methyltin species are not absorbed by Sephadex G-25, and so can be separated from inorganic tin. Both inorganic tin and methyltin species in natural waters at pH 7.4 can be quantitatively retained by passing through small columns of Chelex-100 resin: the methyltin species can then be washed off the resin with 4M nitric acid. Trimethyltin chloride¹¹³Sn in water scarcely interacts with fulvates, humates, kaolinite or montmorillonite but is absorbed bySphagnum peat. Dimethyltin dichloride-¹¹³Sn reacts significantly with all the above materials after 2 hours equilibration. Methyltin trichloride-¹¹³Sn interacts weakly in alkaline solutions.     

A generator for preparation of carrier-free224Ra

The construction of a dynamic generator for the separation of carrier-free²²⁴Ra is described. The mother²²⁸Th was extracted on the top of the column with di-(2-ethylhexyl)phosphoric acid on hydrophobized Chromosorb W DMCS. The function of the generator was checked during 6 months by measuring the decontamination of²²⁴Ra from²²⁸Th. Simultaneously the yield of²²⁴Ra was determined as a function of the HCl concentration and of the means of milking. The best results were obtained with 0.01–0.1M HCl; the yield was about 75% of the theoretical value, and the²²⁴Ra contained less than 0.01% of²²⁸Th.     

Oxidation studies with peroxomonophosphoric acid. II. A kinetic and mechanistic study of dimethyl sulfoxide oxidation in acid and alkaline media

The kinetics of dimethyl sulfoxide (DMSO) oxidation by peroxomonophosphoric acid (PMPA) in aqueous medium at 308 K and I = 0.4 mol/dm³ follow the rate expressions In the pH range from 0 to 2, where k₁ and k₂ are 5.092 × 10^?1 dm³/mol sec and ? 0, respectively; in the pH range from 4 to 7, where k₂ = 8.127 × 10^?3 and k₃ = 2.90 × 10^?3 dm³/mol sec; and in the pH range from 10 to 13.6, where k₄ ? 0, and k₅ = 3.08 × 10^?2 dm³/mol sec. The reaction is interpreted in terms of mechanisms involving an electrophilic and a nucleophilic attack of the peroxomonophosphoric acid species, respectively, in acid and alkaline regions, on the sulfur atom of the sulfoxide molecule giving rise to S-type transition states followed by oxygen-oxygen bond fission to form the products.     

Separation and electrodeposition of226Ra

The chemical behavior of calcium, barium and radium in the ion exchange resins Dowex 50W-X8, AG 50W-X8 and Merk I in the presence of ammonium tartrate, EDTA, and citrate has been studied. No differences were observed in results while using any one of the three resins. Calcium, barium and radium were fixed to the exchange column at pH 4.8 EDTA solution. Calcium was eluted in an EDTA solution at pH 5.3, barium and radium between pH 8–11. Elution in citrate media for calcium was achieved at pH 6.1 and for radium at pH 10. In ammonium tartrate, calcium was eluted at pH 6, barium and radium at pH 11.5. Radium was also eluted from the ion exchange resins with a 2M nitric acid solution. The radium free of calcium was electrodeposited onto a stainless steel disc cathode using a 0.1 M potassium fluoride solution, pH 12–14, with a yield of >50%. The energies of²²⁶Ra were analyzed through high resolution -spectra. The²²⁶Ra utilized for these experiments was separated from Mexican carnotite.     

Hydrothermal treatment of microcrystalline cellulose under mild conditions: characterization of solid and liquid-phase products

Microcrystalline cellulose (MCC) particles were subjected to hydrothermal treatment using an autoclave with temperatures ranging from 200 to 250 °C and reaction times ranging from 20 to 100 min. The structure and chemical composition of the reacted solid phase was analyzed by X-ray diffraction, thermo-gravimetric analysis, FTIR spectroscopy and ¹³C-NMR spectroscopy. The relative composition of the water-soluble products was determined by one-dimensional ¹H-NMR and two-dimensional homo and hetero-nuclear NMR spectroscopy. Within the experimental temperature and treatment time ranges, the crystallinity of the reacted solid phase was found to be mostly dependent on the treatment temperature while the aqueous solution was found to change with both temperature and treatment time. At the maximum temperature employed in this study (250 °C), the solid products are similar to amorphous oxidized carbon with glucose as the main water-soluble product. At lower temperatures the particles are unconverted MCC and the liquid products are primarily levulinic acid, formic acid and acetic acid with smaller quantities of 5-hydroxymethyl-furfural and glucose. Heterogeneous and liquid phase reaction-schemes are proposed to explain the observed solid and water-soluble products as a function of temperature and treatment time.