Determination Of Trace Uranium Research Articles

Determination of U(VI) by differential pulse stripping voltammetry using a polydopamine/reduced graphene oxide nanocomposite modified glassy carbon electrode

A novel mercury-free electrochemical sensor for uranium has been fabricated with two-dimensional polydopamine-reduced graphene oxide (PDA-rGO) composites, which is obtained through a simple self-polymerization of dopamine monomers on GO surface. Morphological characterization displayed that PDA was well coated on the rGO and the PDA-rGO composites exhibited a rougher structure. Furthermore, the introduction of PDA greatly increased the amount of functional groups, and PDA-rGO showed significantly enhanced detection activity for uranium. The influence of several experimental parameters such as pH of supporting electrolyte, accumulation time and PDA-rGO amount on the sensitivity of uranium measurement were studied. Under the best conditions, the PDA-rGO electrode could detect U(VI) concentration from 0.1 to 50 μmol L−1 with a detection limit of 0.05 μmol L−1. Besides, the developed sensor exhibited higher selectivity and stability, suggesting that the proposed uranium sensor has broad application prospects in the determination of trace uranium.

Determination of trace uranium in waste using a gamma-ray measurement system

Much metal waste of various shapes is generated during decommissioning of uranium processing facilities. If these uranium concentrations are confirmed to be below the clearance level, the generation of radioactive waste can be reduced. In this paper, measurement tests were performed on a mock-up of typical metal waste generated by the decommissioning using the clearance measurement device equipped with NaI detectors, and the results were compared with the simulation results by the MCNP code. Investigation results showed the proper placement of dismantled materials in a drum can be estimated by evaluating the detection efficiency of each waste placement by simulation in advance. Moreover, it was confirmed that the discrepancy ratios between simulation and measurement results were within 35% at a total uranium activity concentration of 0.1 Bq g−1. From the above, it was found that the uranium concentration below the clearance level can be confirmed even if the error is included, and the clearance level can be safely verified by considering the discrepancy ratios between the simulation result and the experimental result.

Determination of trace uranium in thorium matrix by laser induced fluorimetry after separation of thorium by its fluoride precipitation using NH4HF2

Abstract Thorium, a major element in thorium matrix, quenches uranium fluorescence when it is present above the ratio (Th/U) of 2000 in conventional pellet fluorimetry determination of uranium. A single step ‘sample digestion cum thorium fluoride precipitation’ with NH4HF2 has been developed for separation of bulk thorium as hydrated thorium fluoride precipitates. Uranium in aqueous solution is extracted into ethyl acetate and stripped into pyrophosphate medium (pH ∼ 7), prior to its laser induced fluorimetry determination. Optimizations of certain parameters such as the effects of fluoride flux, mineral acid, temperature and time, stripping solution, diverse ions etc. are discussed in detail. The method has been validated by analyzing a set of synthetic mixtures and certified reference materials of rock samples such as SY-2, SY-3, GSP-2, NKT-1 and CG-2 doped with a large excess of thorium. This method has been applied for the determination of microgram to nanogram uranium in thorium rich rocks and synthetic nuclear grade ThO2 with high degree of accuracy and precision. This is the improvement of the existing method which involves two liquid-liquid solvent extraction separation of thorium and uranium using the chelating agent 2,3-dihydroxynaphthalene at the different pH, compared to one solvent extraction separation of uranium in the present method, because separation of thorium by precipitation as its fluoride has already been carried out during sample digestion step itself. The proposed method involving ammonium hydrogen fluoride in combination with laser induced fluorimetry is simple, rapid, cost effective and more eco-friendly.

Determination of Trace Uranium in Nuclear Grade Sponge Zirconium by Inductively Coupled Plasma Mass Spectrometry

In order to ensure the quantify control of the nuclear grade zirconium sponge, the inductively coupled plasma mass spectrometry(ICP-MS) was used to determine the trace uranium in the nuclear grade sponge zirconium. The sample was dissolved quickly by HNO3-HF solution. The analysis of the choices of isotope mass number and internal standard isotope, and the influence of matrix showed that the effective correction of matrix effect and the interference caused by the instrument drift can be accomplished, while 232Th was used as an internal standard. When the uranium standard stock solution with concentrations of 0.20 μg/g, 1.00 μg/g and 1.50 μg/g were respectively added to the samples, the recovery rates were between 94% and 99%, with corresponding maximum Relative Standard Deviation(RSD) of 5.1%, relative standard uncertainty of 5.9%. The detection limit was 0.001 μg/g. This method was employed to determine the actual sample, and the results meet the requirement of the uranium content in the nuclear grade sponge zirconium.

An extractive pellet fluorimetric determination of trace uranium in thorium rich samples

An extractive pellet fluorimetry determination of trace uranium in thorium rich samples has been developed. This is based upon a solvent extraction system which completely separates both the elements uranium and thorium from each other. Thorium as a neutral complex with 2,3-dihydroxynaphthalene at pH 4–6 is extracted into ethylacetate and then uranium-2,3-dihydroxynaphthalene anionic complex is extracted into another batch of ethylacetate at pH 11–12 under the influence of a counter cation, cetyltrimethylammonium ion. This method has been applied for the determination of trace uranium in synthetic nuclear grade thorium oxide and thorium rich mineralized rock with high degree of accuracy and precision.

Determination of trace uranium (VI) using its self-assembly with a tetradentate–monodentate ditopic ligand by resonance light scattering

ABSTRACTWe describe here a resonance light scattering (RLS) method for uranium (VI) detection by using phosphorylethanol-amido-salophen (PAS) as optical probe. PAS is a tetradentate–monodentate ditopic ligand in which the tetradentate and monodentate ligands are salophen moiety and phosphate group, respectively. PAS can chelate uranyl with its salophen moiety. The chelated uranyl can connect phosphate group in another PAS through coordination reaction. This causes the self-assembly of PAS with uranyl to form a metallo-supramolecular polymer, resulting in a production of strong RLS signal. The RLS method was established based on the self-assemble. The RLS intensity is linearly related to the concentration of uranium (VI) in the 0.8–32 ng mL−1 range, with a detection limit of 0.24 ng mL−1 detection limit under optimal conditions. The method was successfully applied to determine uranium (VI) in environmental water samples with the recoveries between 97.1% and 102.6%.

Determination of trace uranium by a photo-catalytic resonance fluorescence method coupled with dual cloud point extraction

(1) Extracting and purifying uranium in complex samples by dCPE with [UO22+–SA1]. (2) Detecting uranium super sensitively by a photocatalytic RF method with [UO22+–SA2]. (3) Coupling with separation, purification and analysis procedures exhibited a number of advantages, including high selectivity, high sensitivity and low cost.

Separation and determination of trace uranium using a double-receptor sandwich supramolecule method based on immobilized salophen and fluorescence labeled oligonucleotide

A double-receptor sandwich supramolecule method for the separation and determination of trace uranium was proposed in this paper. One receptor is a salophen which can react with uranyl to form a uranyl-salophen complex, and another receptor is an oligonucleotide which can bind uranyl to form oligonucleotide-uranyl-salophen supramolecule. The salophen was immobilized on the surface of silica gel particles and used as the solid phase receptor for separating uranium from solution. The oligonucleotide was labeled with a fluorescent group and used as the labeled receptor for quantitatively analyzing uranium. In the procedure of separation and determination, uranyl ion was first combined with the solid phase receptor and then conjugated with the labeled receptor to form the sandwich-type supramolecule. The labeled receptor in the sandwich supramolecule was then eluted and determined by fluorescence analysis. The experimental results demonstrate that this method has a number of advantages such as high selectivity, excellent pre-concentration capability, high sensitivity, good stability and low cost. Under optimal conditions, the linear range for the detection of uranium is 0.5–30.0ngmL−1 with a detection limit of 0.2ngmL−1. The proposed method was successfully applied for the separation and determination of uranium in real samples with the recoveries of 95.0–105.5%.

Pre-concentration and determination of trace uranium (VI) in environments using ion-imprinted chitosan resin via solid phase extraction

The uranyl-ion-imprinted and non-imprinted cross-linked chitosan resins possessing quinoline-8-ol moiety have been prepared. In all the cases, a significant imprinting effect was noticed on comparing percent extraction of uranium (VI). The resulting ion-imprinted resin was used for solid phase extractive preconcentration of uranium (VI) prior to its determination by spectrophotometry. Experimental variables that influence the quantitative extraction of uranium (VI) were optimized by both static and column methods. The retention capacity found for uranium (VI) was 218 mg g-1 of resin which is higher than the corresponding non-imprinted resins and other solid phase extraction sorbents possessing quinoline-8-ol moiety. The optimum pH range was 4.5-7.0. Uranium adsorbed was easily and quantitatively eluted with 1 mol L-1 HCl (10 mL) at a flow rate of 2 mL min-1. Interference studies showed a high tolerance of diverse ions and electrolyte species. The limit of detection was 2 µg L-1 and the dynamic linear range was 5-100 µg L-1. The accuracy of the developed method was tested with one uranium ore standard reference material. Furthermore, the proposed method was successfully applied for the determination of uranium in contaminated soil and sediment samples.

Spectrochemical determination of trace uranium by an argon-stabilized U-shaped DC arc

An argon-stabilized U-shaped DC arc with the system for aerosol introduction was used for uranium determination. High uranium toxicity suggests the necessity of developing as sensitive methods as possible for U detection in various natural samples and complex matrices. By optimizing the operation conditions of U-shaped arc plasma and by applying an appropriate computer program that performs temporal integration of recorded signals, the measurement precision as well as the concentration sensitivity were improved, and the detection limit was lowered. Uranium detection limit, obtained by the application of U-shaped arc plasma during different integration times, decreases by increasing integration time. By increasing this time from 1 to 30 s, the detection limit was 37 times lower and the lowest detection limit is 0.07 μg/mL. The detection limit achieved by this method is comparable with the detection limits obtained by such methods as inductively coupled plasma-atomic emission spectroscopy (ICP-AES), direct coupled plasma-atomic emission spectroscopy (DCP-AES), and microwave induced plasma-atomic emission spectroscopy (MIP-AES).

Micelle‐Mediated Extraction for Direct Spectrophotometric Determination of Trace Uranium(VI) in Water Samples

The possibility of using Dibenzoylmethane (DBM) for uranium(VI) concentrating by the way of micellar extraction at cloud point temperature and later spectrophotometric determination was investigated. Under the optimum conditions, preconcentration of 50 mL of water samples in the presence of 0.2% (w/v) octylphenoxypolyethoxy ethanol (Triton X‐114), 2×10−4 mol L−1 DBM and 2×10−3 mol L−1 buffer solution (pH=9) gave a limit of detection 11 ng mL−1, and the calibration graph was linear in the range of 15–300 ng mL−1. The recovery under optimum working conditions was higher than 98%. The proposed method has been applied to the spectrophotometric determination of uranium(VI) in natural water samples after cloud point extraction with satisfactory results.

Simultaneous determination of trace uranium and vanadium in biological samples by radiochemical neutron activation analysis

A radiochemical neutron activation analysis (RNAA) for simultaneous determination of uranium and vanadium in a single sample at trace levels is described. The method is based on post-irradiation wet-ashing and solvent extraction of vanadium with N-benzoyl-N-phenyl-hydroxylamine reagent. From the remaining aqueous phase, uranium is extracted into a toluene solution of tri-n-butyl phosphate. The chemical yields are determined spectrophotometrically for vanadium and by gamma-counting of the added natural uranium carrier for uranium. The method was evaluated by the analysis of reference materials and the results showed a good agreement with the certified values. The method was applied to the determination of vanadium and uranium in five military total diet samples in Slovenia.

Selective determination of trace uranium by stripping voltammetry following adsorptive accumulation of the uranium—cupferron complex

Selective determination of trace uranium by stripping voltammetry following adsorptive accumulation of the uranium—cupferron complex

Trace uranium analysis of various waters by fission track technique

Abstract This paper has given by fission track technique the results of the determination of trace uranium in various waters which include Beijing tap water, river water, atmosphere precipitation, spring water and lake ( or reservoir ) water. In tap water, the uranium contents varied from 1.3 to 8.8μg/lit; in river water, it varied from 0.03 to 1.30μg/lit; in atmospheric precipitation, 0.008 to 1.5μg/lit; in spring water, 0.006 to 1.62μg/lit and in lake ( or reservoir ) water, 0.056 to 1.56μg/lit. The results of the method have been compared with those of neutron activation analysis and others. The variety of the uranium contents the various water source has been discussed briefly in the light of geographical environment. The standard deviation of the method is not greater than 10%.

Preparation of soluble ternary heteroazo dye complexes for the spectrophotometric determination of trace uranium(VI)

The complexing ability of typical pyridylazo, quinolylazo and thiazolylazo dyes with uranium(VI) in aqueous ethanol media are investigated in the presence and absence of aromatic carboxylic acid. Uranium(VI) forms solubilized ternary complexes with PAN, PAR, TAM, 5-Br-PADAP, 3,5-diBr-PADAP and QADAP in 48% ethanol solution containing sufficient amounts of sulfosalicylic acid and triethanolamine buffer (pH 7.8). Aromatic carboxylic acids contribute to expel the coordinated water molecules from the uranium (VI) moiety and their chelating effects have been explained by ternary complex formation. An increase in molar absorptivity and no shift in the wavelength of maximum absorbance are observed for all uranium(VI) complexes investigated. The 1∶1 stoichiometry of uranuim(VI) and heteroazo dye in the binary complex does not change through ternary complex formation. The molar absorptivity of the uranium(VI)-3,5-diBr-PADAP-sulfosalicylic acid ternary complex at 595 nm is 8.4×104l mol−1 cm−1 and Beer's law is valid up to 2.5gmg ml−1 of uranium(VI). The interferences due to coexisting metal ions can be effectively masked by addition of CyDTA or Ca-CyDTA.

Spectrophotometric determination of trace uranium(VI) as a mixed ligand complex with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol and aromatic carboxylic acid

Spectrophotometric studies on a uranium(VI) ternary complex and its analytical application are described. Uranium(VI) reacts with 5-Br-PADAP to form an unstable chelate, which precipitates on standing in 48% ethanolic aqueous solution. The colour stability of uranium(VI) complex is greatly improved by the presence of aromatic carboxylic acids. For the present purpose, o-hydroxybenzoic acid and its derivatives are best suited. The calibration graph is linear up to 2.6 μg·ml−1 of uranium(VI) at 578 nm. The role of carboxylic acid as an auxiliary ligand is discussed.