Determination of uranium in natural waters after anion-exchange separation

A method is described for the determination of uranium by fluorimetry and spectrophotometry in samples of natural non-saline waters. After acidification with hydrochloric acid, the water sample is filtered and, following the addition of ascorbic acid and potassium thiocyanate, passed through a column of the strongly basic anion-exchange resin Dowex 1-X8 (thiocyanate form). On this exchanger uranium is adsorbed as an anionic thiocyanate complex. After removal of iron and other coadsorbed elements by washing first with a mixture consisting of 50 vol.% tetrahydrofuran, 40 vol.% methyl glycol and 10 vol.% 6 M hydrochloric acid, and then with pure aqueous 6 M hydrochloric acid, the uranium is eluted with 1 M hydrochloric acid. In the eluate, uranium is determined fluorimetrically or by means of the spectrophotometric arsenazo III method. The procedure was used for the routine determination of uranium in water samples collected in Austria.     

Determination of uranium in tap water by ICP-MS

A fast and accurate procedure has been developed for the determination of uranium at microg L(-1) level in tap and mineral water. The method is based on the direct introduction of samples, without any chemical pre-treatment, into an inductively coupled plasma mass spectrometer (ICP-MS). Uranium was determined at the mass number 238 using Rh as internal standard. The method provides a limit of detection of 2 ng L(-1) and a good repeatability with relative standard deviation values (RSD) about 3% for five independent analyses of samples containing 73 microg L(-1) of uranium. Recovery percentage values found for the determination of uranium in spiked natural samples varied between 91% and 106%. Results obtained are comparable with those found by radiochemical methods for natural samples and of the same order for the certified content of a reference material, thus indicating the accuracy of the ICP-MS procedure without the need of using isotope dilution. A series of mineral and tap waters from different parts of Spain and Morocco were analysed.     

Solid phase extraction of trace amounts of uranium(VI) from water samples using 8-hydroxyquinoline immobilized on surfactant-coated alumina

A simple and reliable method has been developed for the determination of uranium(VI). The method is based on the separation and preconcentration of uranium(VI) using a column packed with 8-hydroxyquinoline immobilized on surfactant coated alumina prior to its spectrophotometric determination with arsenazo III. The effect of pH, sample flow rate and volume, elution conditions, and foreign ions on the sorption of uranium(VI) has been investigated. A preconcentration factor of 200 was achieved by passing 1000 mL of sample through the column. The relative standard deviation for 10 replicate analyses at the 100 ng/mL level of uranium(VI) was 2.1% and the detection limit was 0.12 ng/mL. The method was success-fully applied to the determination of uranium in natural water samples. The accuracy was assessed through recovery experiments and the analysis of a certified reference material.     

Solid phase extraction of trace amounts of uranium(VI) from water samples using 8-hydroxyquinoline immobilized on surfactant-coated alumina

A simple and reliable method has been developed for the determination of uranium(VI). The method is based on the separation and preconcentration of uranium(VI) using a column packed with 8-hydroxyquinoline immobilized on surfactant coated alumina prior to its spectrophotometry determination with Arsenazo III. The effect of pH, sample flow rate and volume, elution conditions, and foreign ions on the sorption of uranium(VI) has been investigated. A preconcentration factor of 200 was achieved by passing 1000 mL of sample through the column. The relative standard deviation for 10 replicate analyses at the 100 ng/mL level of uranium(VI) was 2.1% and the detection limit was 0.12 ng/mL. The method was successfully applied to the determination of uranium in natural water samples. The accuracy was assessed through recovery experiments and the analysis of a certified reference material.     

Development of method for determination and preconcentration of uranium in water samples using XAD-4 resin loaded with Br-PADAP

In the present work, a minicolumn of XAD-4 loaded with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (Br-PADAP) is proposed as a preconcentration system for uranium determination in well, tap and mineral water samples by spectrophotometer using arsenazo III as the chromogenic reagent. Initially, a two-level (2³) full factorial design was used for the preliminary evaluation of three factors, involving the following variables: sampling flow rate, elution flow rate, and pH. This design has revealed that, for the studied levels, buffer concentration and pH were significant factors. When the experimental conditions established in the optimization step were pH = 8.6, and an elution flow rate of 8.6 mL min^?1 using 0.5% m/v ascorbic acid, this system has allowed for the determination of uranium with a detection limit (LOD) (3σ/S) of 0.05 μg L^?1 and a quantification limit (LOQ) (10σ/S) of 0.16 μg L^?1. The precision expressed as the relative standard deviation (R.S.D.) of 0.8% and 1.9% at 10.0 and 1.0 μg L^?1, respectively- and a preconcentration factor of 184.5 for a sample volume of 50.0 mL. Accuracy was confirmed by uranium determination in the standard reference material, NIST SRM 1566b trace element units in Oyster Tissue samples, and spike tests with recuperations ranging from 93.2 to 105%; the procedure were applied for uranium determination in tap water, well water, and drinking water samples collected from Caetité and Cruz das Almas Cities, Bahia, Brazil. Five water samples were analyzed the uranium concentrations varied from 0.50 to 2.07 μg L^?1     

Determination of U and Ra in rock samples by gamma-spectrometric method

A gamma-spectrometric method independent of radon escape for the determination of U and Ra in rock samples based on the 63 keV and 1001 keV as well as 185 keV lines is described and discussed. A simple experimental procedure is given for the determination of the self-absorption factor. The method has been applied for the determination of uranium and radium in rock samples from Morocco containing uranium between 17.5 wt.% and 0.026 wt.%. The limits of determination, at 95% confidence level and 10% standard deviation, for the 63 keV and 1001 keV lines were found to be 0.075 wt.% and 0.62 wt.%, respectively, using samples of 6 g and chosing 1 h measuring time.     

Separation of uranium from iron in ground water samples using ion exchange resins

Uranium determination in environmental samples is faced with problems due to presence of iron and other major elements. Iron is also used many a times for pre-concentration of uranium and actinides. Separation of milligram quantity of Fe from microgram quantity of uranium becomes essential during the estimation step. A simple two step procedure has been standardized for separating uranium and iron using anion exchange in 0.025 M H₂SO₄. Quantitative recovery of uranium was obtained as well as good separation from iron. This method was applied for estimation of uranium in water samples.     

Adsorptive Cathodic Stripping Voltammetric Determination of Uranium(VI) in Presence of N‐Phenylanthranilic Acid

N‐Phenylanthranilic acid was used as a complexing agent for determination of uranium(VI) by adsorptive cathodic stripping voltammetry. Under the optimal experimental conditions of the experimental parameters, the peak current was proportional to the concentration of U(VI) in the range 0.75–30 ng mL^?1 and the detection limit was 0.036 ng mL^?1. The influence of possible interferences was investigated. The method was applied for determination of uranium in waste water from uranium conversion facility and natural water samples. Application of the method for simultaneous determination of U(VI) and Cu(II) showed that these ions could be simultaneously determined in a single scan at relatively wide concentration range.     

Spectrophotometric determination of uranium(VI) with 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol in the presence of anionic surfactant

A highly sensitive method for spectrophotometric determination of uranium has been devised. The method is based on formation of a red-violet 1:2 (metal:ligand) complex from the reaction of uranium(VI) with 2-(3,5-dibromo-2-pyridylazo)-5-diethylaminophenol (3,5-diBr-PADAP) in the presence of an anionic surfactant, sodium lauryl sulphate. Its molar absorptivity is found to be 9.1 x 10(4)l.mole(-1).cm(-1). The absorbance is constant in the range pH 8.4-9.9 Beer's law is obeyed for 0-1.4 mug/ml concentrations of uranium. In the presence of DCTA the method is selective for uranium, and can be used for the determination of trace amounts of uranium in water samples.     

Application of ion-exchange separations to determination of trace elements in natural waters-IX: simultaneous isolation and determination of uranium and thorium

A method is described for the determination of uranium and thorium in samples of natural waters. After acidification with citric acid the water sample is filtered and sodium citrate and ascorbic acid are added. The resulting solution of pH 3 is passed through a 4-g column of Dowex 1 x 8 (citrate form) on which both uranium and thorium are adsorbed as anionic citrate complexes. Thorium is eluted with 8M hydrochloric acid and separated from co-eluted substances by anion-exchange in 8M nitric acid medium on a separate 2-g column of the same resin in the nitrate form. After complete removal of iron by washing with a mixture consisting of IBMK, acetone and 1M hydrochloric acid (1:8:1 v v ) and treatment of the resin with 6M hydrochloric acid, the uranium is eluted from the 4-g column with 1M hydrochloric acid. In the eluate thorium is determined spectrophotometrically (arsenazo III method) while fluorimetry is employed for the assay of uranium. The procedure was used for the determination of uranium and thorium in numerous water samples collected in Austria, including samples of mineral-waters. The results indicate that a simple relationship exists between the uranium and thorium contents of waters which makes it possible to calculate the approximate thorium content of a sample on the basis of its uranium concentration and vice versa.     

Rapid and interference free determination of ultra trace level of uranium in potable water originating from different geochemical environments by ICP-OES

Direct determination of uranium in the concentration range of 8 μg L⁻¹ to mg L⁻¹ in water samples originating from different geochemical environments has been done using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). Uranium detection with 2–3% RSD (relative standard deviation) has been achieved in water samples by optimizing the plasma power, argon and sheath gas flow. These parameters were optimized for three different emission lines of uranium at 385.958, 409.014 and 424.167 nm. Interference arising due to the variation in concentration of bicarbonate, sodium chloride, calcium chloride, Fe and dissolved organic carbon (DOC) on the determination of uranium in water samples was also cheeked as these are the elements which vary as per the prevailing geochemical environment in groundwater samples. The concentration of NaHCO₃, CaCl₂ and NaCl in water was varied in the range 0.5–2.0%; whereas Fe ranged between 1 and 10 μg mL⁻¹ and DOC between 0.1–1%. No marked interference in quantitative determination of uranium was observed due to elevated level of NaHCO₃, CaCl₂ and NaCl and Fe and DOC in groundwater samples. Concentration of uranium was also determined by other techniques like adsorptive striping voltametry (AdSv); laser fluorimetry and alpha spectrometry. Results indicate distinct advantage for uranium determination by ICP-OES compare to other techniques.     

Preconcentration of trace amounts of uranium in water samples on octadecyl silica membrane disks modified by bis(2-ethylhexyl) hydrogen phosphate and its determination by alpha-spectrometry without electrodeposition

A simple and reliable method for the selective extraction and determination of uranium in water using octadecyl-bonded silica membrane disks modified with bis (2-ethylhexyl) hydrogen phosphate and alpha-spectrometry is described. Extraction efficiency and influence of sample matrix, optimum amount of extractant, type and minimum amount of organic eluent and flow rates were evaluated. The limit of detection of the proposed method is 40 ng per 1000 ml. The influence of potential interfering cations in water samples on the recovery of U(VI) was investigated. The method was successfully applied to the extraction and determination of uranium in natural water.     

Spectrophotometric method for the determination of vanadium in uranium rich hydrogeochemical samples using pyridyl azo resorcinol (PAR)

A simple and precise method has been developed for the determination of traces of vanadium(V), using 4-(2 pyridyl azo) resorcinol, in natural water samples, containing very high concentrations of uranium. CDTA-pyrophosphate buffer has been used for masking interferants, including uranium which otherwise interferes above 125 ppb. The reaction of vanadium with PAR in the presence of buffer requires a waiting period of 45 min. The Sandell sensitivity of the method is 0.003 microg/ml, at 545 nm at an optimum pH of 6.5 +/- 0.2. The precision of the method is +/- 15% at the 100 ppb level of vanadium(V). The method has been successfully applied to a number of natural water samples during hydrogeochemical exploration.     

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

In 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.     

X-ray spectrometric method for the determination of uranium in solution by a cellulose disc technique

An X-ray fluorescence spectrometric method is described for the determination of uranium in liquid samples by absorbing drops of solution on cellulose discs. Internal standards thorium, strontium or yttrium are added in the uranium solution to follow the non-uniform absorption of the liquid on the disc. A precision of better than ±0.5% is obtained for uranium determination with all the three internal standards. The method was also employed to determine uranium in the presence of plutonium and americium without any interference effects.     

Fluorimetric determination of uranium(VI) in waters by flow-injection analysis after preconcentration on a silica gel microcolumn

A method was developed for the selective determination of trace concentrations of uranium(VI) by flow-injection analysis (FIA) with fluorimetric detection. Uranium(VI) is selectively separated and/or pre-concentrated from a volume up to 20 ml on an activated silica gel microcolumn (2 x 40 mm) from a medium of 0.03M EDTA, 0.06M tartrate, and/or 0.05M NaF at pH = 9.3. After washing the column the uranium is eluted with a mixture of 1.33M sulphuric and phosphoric acids and determined with a relative standard deviation not exceeding 6% for concentrations in the range 10-250 mug/l. The detection limit was estimated to be 0.1-0.2 mug of uranium. The method has been verified on artificial water samples with high content of the interfering elements and applied to analysis of waste and natural waters.     

Determination of uranium in pore water from coastal sediment by standard addition ICP-MS analysis

Mass spectrometry using ICP-MS was applied to determine the uranium content in pore water samples through the standard addition method. This method requires less than 0.2 ml of a water sample, without any chemical separation. The sample solution (50 mg) was diluted with ∼1% HNO₃ to make a total weight of 5.00 g, after the addition of uranium standard. The method introduced 1% of analytical precision for measured uranium in the samples. This rapid and simple technique allows multi-trace elemental quantification using mixed standards. The behavior of uranium in pore water and the variations of uranium content at different depths of pore water are discussed.     

Rapid laser fluorometric method for the determination of uranium in soil, ultrabasic rock, plant ash, coal fly ash and red mud samples

A simple and rapid laser fluorometric determination of trace and ultra trace level of uranium in a wide variety of low uranium content materials like soil, basic and ultra basic rocks, plant ash, coal fly ash and red mud samples is described. Interference studies of some common major, minor and trace elements likely to be present in different, geological materials on uranium fluorescence are studied using different fluorescence enhancing reagents like sodium pyrophosphate, orthophosphoric acid, penta sodium tri-polyphosphate and sodium hexametaphosphate. The accurate determination of very low uranium content samples which are rich in iron, manganese and calcium, is possible only after the selective separation of uranium. Conditions suitable for the quantitative single step extraction of 25 ng to 20 μg uranium with tri-n-octylphosphine oxide and single step quantitative stripping with dilute neutral sodium pyrophosphate, which also acts as fluorescence enhancing reagent is studied. The aqueous strip is used for the direct laser fluorometric measurement without any further pretreatment. The procedure is applied for the determination of uranium in soil, basalt, plant ash, coal fly ash and red mud samples. The accuracy of the proposed method is checked by analyzing certain standard reference materials as well as synthetic sample with known quantity of uranium. The accuracy and reproducibility of the method are fairly good with RSD ranging from 3 to 5% depend upon the concentration of uranium.     

X射线荧光光谱法同时测定矿石中铀和钍

建立了X射线荧光光谱法测定矿石样品中铀、钍含量的快速分析方法。采用高压粉末制样法,对不同含量的放射性样品的压片压力、粒径、含水率、用量等处理条件到进行单因素实验。在400 MPa压力下压制,克服了低压制样的弊端,制备的样片表面光滑、致密,大幅改善了制样重现性,有效地减少了部分基体效应,铀校准曲线的标准偏差从0.053%降到0.0071%,钍校准曲线的标准偏差从0.062%降到0.0057%。经国家一级标准物质验证,表明方法准确、可靠,能满足样品中铀、钍含量日常分析要求。     

Determination of uranium in water based on enzyme inhibition using a wireless magnetoelastic sensor

The aim of this paper is to develop a wireless magnetoelastic sensing method for the determination of uranium in water based on the inhibitory effect of uranyl cation to α-amylase. In this method, a wireless sensor used for detecting uranium was fabricated by immobilizing a layer of starch gel on the surface of a magnetoelastic foil. When the sensor was in a solution containing α-amylase, the α-amylase catalyzed the hydrolyzation of starch, causing a resonance frequency shift of the sensor. Meanwhile, the catalytic hydrolyzation of starch was inhibited by uranium presented in the above solution, resulting in a decrease in the resonance frequency shift of the sensor. Consequently, the amount of uranium could be determined by measuring the resonance frequency shift. The influence of manifold variables on the determination was investigated in details. A linear range was found to be 9.2 to 103.5?µg?L^?1 under optimal conditions with a detection limit of 3.6?µg?L^?1. The method was applied to the determination of uranium in environmental water samples with satisfactory results.