Uranium In Aqueous Samples Research Articles

Quality Assurance for In Situ Uranium Concentration Measurements of Aqueous Samples from Mineral Processing Studies Using a Portable XRF Analyser in Compliance with ISO/IEC 17025 Requirements

The method developed in this article aims to control the quality of uranium leaching and processing measurements at the Jordan Atomic Energy Commission, through the instant determination of uranium in aqueous samples without chemical preparation using portable X‐Ray Fluorescence (pXRF) analysis. Acidic and alkaline samples were analysed via pXRF then compared with results from ICP‐MS/ICP‐AES. The pXRF method validation, in view of ISO/IEC 17025:2017 requirements, was applied to real samples and simulated uranium ore solutions from single uranium and two other certified reference materials. The slopes acquired from correlations between pXRF results and reference values were 1.026, 1.021 and 0.9664, respectively, with correlation coefficients (r2) approaching 1.0. Precision calculations showed values < 5% RSD for samples having uranium contents > 10 mg l−1, while this value was ±10% at 5 mg l−1. The detection and quantification limits were determined as 2.5 and 7.7 mg l−1, respectively. Relative expanded uncertainty was found to equal 12.5% with a coverage factor k = 2 at the quantification limit. Finally, a paired t‐test and linear regression combining the pXRF results and reference values obtained by ICP‐MS and ICP‐AES demonstrated no significant difference at the 95% confidence level. This work eventually led to the laboratory’s ISO/IEC 17025:2017 accreditation for this method.

Selective Micellar Extraction of Ultratrace Levels of Uranium in Aqueous Samples by Task Specific Ionic Liquid Followed by Its Detection Employing Total Reflection X-ray Fluorescence Spectrometry.

A task specific ionic liquid (TSIL) bearing phosphoramidate group, viz., N-propyl(diphenylphosphoramidate)trimethylammonium bis(trifluoromethanesulfonyl)imide, was synthesized and characterized by 1H NMR, 13C NMR, 31P NMR, and IR spectroscopies, elemental (C H N S) analysis, and electrospray ionization mass spectrometry (ESI-MS). Using this TSIL a cloud point extraction (CPE) or micelle mediated extraction procedure was developed for preconcentration of uranium (U) in environmental aqueous samples. Total reflection X-ray fluorescence spectrometry was utilized to determine the concentration of U in the preconcentrated samples. In order to understand the mechanism of the CPE procedure, complexation study of the TSIL with U was carried out by isothermal calorimetric titration, liquid-liquid extraction, 31P NMR and IR spectroscopies, and ESI-MS. The developed analytical technique resulted in quantitative extraction efficiency of 99.0 ± 0.5% and a preconcentration factor of 99 for U. The linear dynamic range and method detection limit of the procedure were found to be 0.1-1000 ng mL-1 and 0.02 ng mL-1, respectively. The CPE procedure was found to tolerate a higher concentration of commonly available interfering cations and anions, especially the lanthanides. The developed analytical method was validated by determining the concentration of U in a certified reference material, viz., NIST SRM 1640a natural water, which was found to be in good agreement at a 95% confidence limit with the certified value. The method was successfully applied to the U determination in three natural water samples with ≤4% relative standard deviation (1σ).

Micellar extraction assisted fluorometric determination of ultratrace amount of uranium in aqueous samples by novel diglycolamide-capped quantum dot nanosensor

Uranium (U), the naturally occurring toxic radionuclide is soluble in aquatic environment as uranyl ion (UO22+) and hence bioavailable U can affect living organisms adversely. Detection of U in aqueous samples was made simple, cost effective and sensitive by synthesizing a highly specific diglycolamide-capped CdS/ZnS core-shell quantum dot (QD) nanosensor. Its ultratrace level determination was done by conjugating this nanosensor with cloud point extraction (CPE) procedure. In solution the UO22+ ion gets bonded to the diglycolamide group of the QD nanosensor and a direct Föster Resonance Energy Transfer (FRET) mechanism takes place between the UO22+ ion and QD. This results in increase of the QD fluorescence intensity and the phenomenon was used to detect the metal ion concentration. The dynamic linear range (DLR) of the method was found to be 1.0–100ngmL−1 of U in water. The limit of detection (LOD) was found to be 0.03ngmL−1. The developed methodology was validated by measuring the value of U in NIST SRM 1640a which was found to be in agreement with the reported value at 95% confidence level. The method was successfully applied to the U determination in three natural water samples with ≤5% of relative standard deviation (RSD, 1σ).

On-line extraction and determination of uranium in aqueous samples using multi-walled carbon nanotubes-coated cellulose acetate membrane

ABSTRACTIn this work, multi-walled carbon nanotubes (MWCNTs)-coated cellulose acetate membrane was used for on-line extraction and pre-concentration of uranium from aqueous samples prior to inductively coupled plasma optical emission spectrometry (ICP-OES) determination. Sample solutions containing the U(VI)-2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP) complex were passed through the membrane. The adsorbed analyte was subsequently eluted from the membrane with acid, which was directly introduced into the ICP-OES nebuliser. The main variables affecting the pre-concentration and determination steps of uranium were studied and optimised. Under the optimised conditions, the enrichment factor of 150 and the detection limit of 0.16 μg L–1 were obtained. This method was successfully used for determination of uranium in environmental water samples.

Alpha spectroscopic analysis of actinides (Th, U and Pu) after separation from aqueous solutions by cation-exchange and liquid extraction

The radioactivity concentration of 236Pu, 232U and 228Th in aqueous samples has been determined by means of alpha spectroscopy after chemical separation and pre-concentration of the radionuclides by cation exchange and liquid–liquid extraction using the Chelex-100 resin and 30% TBP/dodecan, respectively. Method calibration using a 236Pu standard solution containing the daughter radionuclides results in a detector efficiency of 18% and in a chemical recovery for cation-exchange which is (30 ± 7)%, (90 ± 5)% and (20 ± 5)% for plutonium, uranium and thorium, respectively. The chemical recovery for liquid–liquid extraction is found to be (60 ± 7)%, (50 ± 5)% and (70 ± 5)%, for plutonium, uranium and thorium, respectively. The differences in the efficiencies can be ascribed to the oxidation states, the different actinides present in solution. Taking into account that the electrodeposition of the radionuclides under study is quantitative, the total method efficiency is calculated to be (18 ± 15)%, (46 ± 7)% and (15 ± 5)%, for plutonium, uranium and thorium, respectively, at the mBq concentration range. The detection limit of the alpha spectrometric system has been found to be 0.2 mBq/L, suggesting that the method could be successfully applied for the radiometric analysis of the studied radionuclides and particularly uranium in aqueous samples.

Simultaneous determination of thorium and uranyl ions by optode spectra and chemometric techniques

A sensitive optode was fabricated from a recently synthesized ligand (triazene-1,3-di(2-methoxyphenyl)). Simultaneous determination of thorium and uranium in aqueous samples were performed by this optode in conjunction with partial least squares (PLS) and artificial neural network (ANN) techniques. The measured absorbances at 27 selected wavelengths were used for training. A PLS1 model with 4 and 3 latent variables for thorium and uranium respectively, a PLS2 model with 4 latent variables and a principal component ANN model (4-2-2) with linear transfer function after hidden and output layers were created. Relative error of prediction for PLS1, PLS2 and ANN models in synthetic mixtures were 7.40%, 7.12% and 5.04% respectively.

A new method for simultaneous determination of 226Ra and uranium in aqueous samples by liquid scintillation using chemometrics

In this work, simultaneous determination of low levels of 226 Ra and uranium in aqueous samples were performed by alpha-liquid scintillation counting (LSC) in conjunction with artificial neural network (ANN) and partial least squares (PLS). The counting rates at 73 channels, which were selected by genetic algorithm, were used for training. A PLS model with four latent variables and a principle component ANN model (4-4-2) with linear transfer function after hidden and output layers were created. Total relative error of prediction for PLS and ANN in synthetic mixtures was 18.05% and 24.78%, respectively. The matrix effect was studied by spiking the real samples with radium and uranium. Laser induced fluorescence was used for assessment of uranium prediction results in real samples.

Determination of uranium by liquid scintillation and Cerenkov counting

Three radiometric methods for the determination of uranium in aqueous samples, involving the use of a liquid scintillation counter, have been studied and compared. Uranium is separated and purified by coprecipitation with iron(III) hydroxide followed by an anion-exchange process. The purified uranium in the eluate (0.1 mol l–1 HCl) can either be collected and stored and the Cerenkov radiation from the in-growth of the high-energy β-emitter 234Pa counted, or the uranium can be extracted from the chloride eluate into diethylhexylphosphoric acid in toluene containing appropriate scintillation materials and counted by a liquid scintillation technique. Alternatively, uranyl chloride can be converted into uranyl nitrate, which is then dissolved in 1 ml of 1,4-dioxan, and the solution is subsequently mixed with scintillation solution and counted. In the liquid scintillation methods, both 234U and 238U can be determined, but, by using the Cerenkov method, 238U is measurable in isolation. Several variants of the chemical-separation procedure have been studied in relation to their effect on quenching, sensitivity and accuracy. The background count rates observed were 0.04, 0.075 and 0.213 counts s–1 for the 1,4-dioxan, extraction and Cerenkov techniques, respectively; the lower limit of detection was taken as 3σ of the background. Chemical yields were in the range 80–90%.

Spectrophotometric procedure for the determination of uranium with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol at a nuclear reprocessing facility

A simple method for the determination of uranium in process- and waste-stream samples at a nuclear fuel reprocessing facility that can be applied entirely in a remote environment is described. The method is both sensitive and selective enough to be applicable for almost any uranium determination. Uranium in aqueous samples is extracted as a nitrate complex into 4-methylpentan-2-one (hexone) from an acid-deficient aluminium nitrate salting solution. An aliquot of the hexone extract is then mixed with a solution containing methanol, pyridine and 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (Br-PADAP). The absorbance of the U(VI)-Br- PADAP complex is measured at 580 nm. The detection limit for uranium is 0.8 μg with the linear range extending to 80 μg. Interference studies, modifications for organic samples and solid-containing samples and process laboratory data are presented.

The determination of uranium in aqueous samples by means of a pulsed-source fluorescence spectrometer

Luminescence from aqueous uranyl ions is examined by means of a fluorescence spectrometer with a pulsed xenon light source. Background fluorescence is reduced by using time-based discrimination of the uranyl emission, but interference can still occur from quenchers such as iron(III). Such interferences are reduced by extraction of the uranyl ion into hexane containing trin-n-butyl phosphate, with back-extraction into dilute phosphoric acid before measurement. A detection limit of 5 ng ml −1 is found with a linear calibration range of 0–10 μg ml −1.

Determination of uranium in aqueous samples by laser-induced fluorescence spectrometry

A new pulsed laser method suitable for trace analysis of uranium in plutonium process stream samples containing large quantities of fluorescence quenchers has been developed. This technique includes the extraction of uranium from an aqueous sample into tri-n-butyl phosphate, with subsequent striping into dilute phosphoric acid. A standard addition method is incorporated into the analysis. Analytical data show that a detection limit of 1 ppB for a particular matrix has been achieved. The precision of the analysis is in the range of +/-7% relative standard deviation. Variation of these results with sample matrix and analytical procedure is discussed. 2 figures.

Detection of ultratrace levels of uranium in aqueous samples by laser-induced fluorescence spectrometry

LBL-12583 Preprint t: To be published in Analytical Chemistry DETECTION OF ULTRA-TRACE LEVELS OF URANIUM IN AQUEOUS SAMPLES BY LASER INDUCED FLUORESCENCE SPECTROMETRY Dale L. Perry, Stanley M. Klainer, Harry R. Bowman, Fred P. Milanovich, Tomas Hirschfeld, and Steven Miller April 1981 TWO-WEEK lOAN COPY This is a Ubrar~ Circulating Cop~ which ma~ be borrowed for two weeks. For a personal retention cop~, call Tech. Info. Dioision, Ext. 6782 Prepared for the U.S. Department of Energy under Contract W-7405-ENG-48