The heterometric micro-analysis of cobalt with α-nitroso - β-naphthol. a general study.

1. The reaction between cobaltous or cobaltic and α-nitroso-β-naphthol was extensively studied heterometrically both in water and in alcoholic solutions. The influence of complexing agents and of the acidity on the precipitation of cobalt-α-nitroso-β-naphthol was investigated. In all cases the molar ratios : [Co] [αβ] at the end of the precipitation were established and the possible compounds which were obtained were discussed. 2. Micro-analytical heterometric methods are given for the determination of cobalt or α-nitroso-β-naphthol. The determination can be carried out with precision even in concentrations as low as 0.0001M Co. Conversely, very dilute alcoholic solutions of α-nitroso-β-naphthol may be titrated with precision with a dilute solution of cobalt nitrate. 0.2–0.5 mg cobalt in 20 ml solution are required for the analysis. The error lies between zero and 3%.     

Ultraviolet absorption spectra of α-nitroso β-naphthol and its copper chelate

From a comparative study of the U.V. absorption spectra of α-nitroso-β-naphthol and of β-naphthol in neutral ethanol and in the presence of 0.1N HClO₄ and 0.1N KOH respectively, evidence in favour of the quinone-oxime structure of α-nitroso-β-naphthol has been presented. The spectrum of the copper chelate of α-nitroso-β-naphthol indicates a planar configuration of the complex with considerable resonance between the quinonoid and benzenoid structures of the ligand.     

Extraction of thorium,uranium and cerium from fresh water using manganese dioxide coprecipitation

A manganese dioxide coprecipitation procedure is utilized to replace a time-consuming evaporation step for the extraction of thorium, uranium and cerium from freshwater samples. The average recovery for 20-liter samples is greater than 95% for²³⁴Th and¹⁴⁴Ce. The data indicate that the manganese dioxide coprecipitation process does not affect the recovery of thorium and uranium during our routine analytical procedure.     

A simple method for the determination of natural uranium and226Ra in waters and soils

A procedure for the determination of natural uranium and²²⁶Ra in waters and soils has been carried out and applied to the analysis of samples for environmental radiological monitoring.²²⁶Ra determination consists of co-precipitation with BaSO₄,²²²Rn emanation in toluene and finally liquid scintillation counting. Natural uranium is then determined by a fluorometric technique. This paper describes the method and the conditions that were tested to optimize it. The technique was found to be suitable for the analysis of surface and ground waters, samples from rivers, streams and lakes and soil samples, because of its few steps, short processing time, high recovery percentages and suitable detection limits.     

Epithermal neutron activation determination of uranium in environmental waters by neptunium-239 after preconcentration on activated carbon

A method for the analysis of uranium in natural waters based on preconcentration of uranium on activated carbon, irradiation with epithermal neutrons, and a high resolution gamma-spectrometry of²³⁹Np was developed. The chemical yield of uranium preconcentration is determined by treating a parallel sample to which a known uranium quantity is added. The lower limit of determination amounts to 1.4·10⁻⁸ g uranium per liter. The possible interfering in gamma-spectrometry of neptunium-239 was discussed too. The applicability of the proposed method is shown by the analysis of uranium in sea-, river-, geothermal-, drinking- and rain-water samples.     

Uranium in natural waters sampled within former uranium mining sites in Kazakhstan and Kyrgyzstan

New data are presented on ²³⁸U concentrations in surface and ground waters sampled at selected uranium mining sites in Kazakhstan and Kyrgyzstan and in water supplies of settlements located in the vicinity of these sites. Radiochemical neutron activation analysis (RNAA) was used for ²³⁸U determination in all cases. In addition, for data accuracy assessments purposes, a sub-set of these samples was analysed by high-resolution alpha spectrometry, following standard radiochemical separation and purification. Our data show that drinking waters sampled at various settlements located close to the uranium mining sites are characterised by relatively low uranium concentrations (1.9–35.9 μg L⁻¹) compared to surface waters sampled within the same sites. The latter show high concentrations of total uranium, reflecting the influence from the radioactive waste generated as a result of uranium ore production.     

Determination of uranium is sea water and biological materials by neutron activation after selective preconcentration with 1-(2-pyridylazo)-2-naphthol

Uranium is preconcentrated from sea water, tap water, and solutions obtained by digestion of biological samples, by coprecipitation with 1-(2-pyridylazo)-2-naphthol (PAN). Coprecipitation is most effective at pH 4.5–6.5 with a recovery of 85–94%. In the presence of 0.1 M 1,2-cyclohexylenedinitrilotetraacetic acid (CyDTA) as a masking agent, the method is highly selective for uranium. After neutron activation of the precipitate, uranium can be quantified via the ²³⁹U nuclide with a relatively low background in the region of interest (74 keV). Detection limits are 3–4 ng kg^?1 for 500-ml water samples and 5 μg kg^?1 for 0.5-g biological samples (after digestion). The method can be applied to most environmental samples, as shown by the results for sea water and three standard reference materials.     

Determination of uranium isotopes in environmental samples by alpha-spectrometry

A new and accurate method for the determination of uranium isotopes (²³⁸U, ²³⁴U and ²³⁵U) in environmental samples by alpha-spectrometry has been developed. Uranium is preconcentrated from filtered water samples by coprecipitation with iron(III) hydroxide at pH 9-10 using an ammonia solution and the precipitate is dissolved in HNO₃ and mineralized with H₂O₂ and HF; uranium in biological samples is ashed at 600 °C, leached with Na₂CO₃ solution and mineralised with HNO₃, HF and H₂O₂; uranium in soil samples is fused with Na₂CO₃ and Na₂O₂ at 600 °C and leached with HCl, HNO₃ and HF. The mineralized or leaching solution in 2M HNO₃ is passed through a Microthene-TOPO (tri-octyl-phosphine oxide) column; after washing, uranium is directly eluted into a cell with ammonium oxalate solution, electrodeposited on a stainless steel disk and measured by alpha-spectrometry. The lower limits of detection of the method is 0.37 Bq^.kg^-1 (soil) and 0.22 mBq^.l^-1 (water) for ²³⁸U and ²³⁴U and 0.038 Bq^.kg^-1 (soil) and 0.022 mBq^.l^-1 (water) for ²³⁵U if 0.5 g of soil and 1 litre of water are analyzed. Five reference materials supplied by the IAEA have been analyzed and reliable results are obtained. Sample analyses show that, the ²³⁸U, ²³⁴U and ²³⁵U concentrations are in the ranges of 0.30-103, 0.49-135 and 0.02-4.82 mBq^.l^-1 in waters, of 1.01-7.14, 0.85-7.69 and 0.04-0.32 Bq^.kg^-1 in mosses and lichens, and of 25.6-53.1, 26.4-53.8 and 1.18-2.48 Bq^.kg^-1 in sediments. The average uranium yields for waters, mosses, lichens and sediments are 74.5±9.0%, 80.5±8.3%, 77.8±4.9% and 89.4±9.7%, respectively.     

Sorption of cobalt on modified clinoptilolites

A method of radioactivation analysis has been developed for the substoichiometric determination of cobalt, copper and manganese in glass and glass-making materials. The substoichiometric extraction of cobalt with α-nitroso-β-naphthol was studied and simple procedures are suggested for the determination of the three elements. Cobalt is extracted substoichiometrically as α-nitroso-β-naphtholate into chloroform from solution of pH 6.2, copper as dithizonate in carbon tetrachloride from weak acidic solution, and manganese as tetraphenylarsonium permanganate into chloroform after oxidation to permanganate. Contents from 2 ppm to 3 ppb of cobalt, copper and managanese were analysed in glass-making materials, and it is shown that the method for their determination is reliable and superior in accuracy and reproducibility.     

The new method for the determination of cobalt in sea water by solvent extraction with 2-nitroso-5-diethylaminophenol

Cobalt in sea waters can be determined spectrophotometrically by means of 2-nitroso-5-diethylaminophenol after extraction of the complex into 1,2-dichloro-ethane. No preliminary concentration is needed. Interferences are prevented by masking or by stripping from the organic phase. The method is applicable over the range 0–0.24 μg Co 1^-1 when 1–1 or 2–1 samples are taken. The relative standard deviation is 4% for 0.15 μg Co 1^-1. The stability of cobalt in sea water samples is discussed.     

A micro-heterometric determination of traces of iron (III) in alloys and salts with α-nitroso β-naphthol

Ferric iron constituting approximately 0.01% — 0.1% may be determined by a heterometric titration with α-nitroso-β-naphthol. The solution may contain 99.9% or more of calcium, barium, magnesium, aluminium, chromium, manganese, nickel, cadmium or lead salts. No previous separation is necessary. The α-nitroso-β-naphthol is dissolved in alcohol. The analysed solution must be acidified. No complexing agents are necessary. Citrate or tartrate must be absent. The maximum optical density values which are obtained at the end of the titration are proportional to the amount of iron which is analysed. These maximum values are entirely unaffected by the concentrated salt solutions. The heterometric sensitivity of the reaction between iron and α-nitroso-β-naphthol is three times higher in 50% alcoholic solution than in water. The titration takes about one hour. The error is 0.0—4%.     

Determination of thorium,uranium and plutonium isotopes in atmospheric samples

A new procedure for the radiochemical measurements of thorium, uranium and plutonium in atmospheric samples is described. Analysis involves coprecipitation of these actinides with iron hydroxide from a 40-to 50-dm³ sample of rainwater, followed by radiochemical separation and purification procedures by the use of ion exchange chromatography (Dowex AG1×8) and solvent extraction. The new procedure enables one to determine the isotopes of thorium, uranium and plutonium, which are found in rainwater at extremely low concentrations, with a chemical yield ranging from 60 to 80%.     

Dosage du cobalt dans les aciers 188 base sur la formation du 60mco par activation aux neutrons thermiques

A method for the determination of cobalt in $\text{18}\text{8}$ steels, based on formation of ^60mCo is proposed. Most of the iron is extracted, then cobalt is extracted as its α-nitroso-β-naphthol complex into toluene. The losses are determined exactly. A determination is complete within 2 h with a precision of ±9% ; the limit of sensitivity is 2 μg of cobalt. The results obtained (average 350 p.p.m.) are compared with results obtained spectrophotometrically (average 368 p.p.m.).     

Simultaneous spectrophotometric determination of trace amounts of uranium, thorium, and zirconium using the partial least squares method after their preconcentration by α-benzoin oxime modified Amberlite XAD-2000 resin

A new solid phase extraction method for separation and preconcentration of trace amounts of uranium, thorium, and zirconium in water samples is proposed. The procedure is based on the adsorption of U(VI), Th(IV) and Zr(IV) ions on a column of Amberlite XAD-2000 resin loaded with α-benzoin oxime prior to their simultaneous spectrophotometric determination with Arsenazo III using orthogonal signal correction partial least squares method. The enrichment factor for preconcentration of uranium, thorium, and zirconium was found to be 100. The detection limits for U(VI), Th(IV) and Zr(IV) were 0.50, 0.54, and 0.48 μg L⁻¹, respectively. The precision of the method, evaluated as the relative standard deviation obtained by analyzing a series of 10 replicates, was below 4% for all elements. The practical applicability of the developed sorbent was examined using synthetic seawater, natural waters and ceramic samples.     

A gravimetric and an X-ray fluorescence method for the determination of rubidium in Rb2U(SO4)3

Chemical characterization of rubidium uranium(IV) trisulfate, Rb₂U(SO₄)₃, a new chemical assay standard for uranium requires accurate analysis of rubidium. A gravimetric and an X-ray fluorescence method (XRF) for the determination of rubidium in this compound are described. In the gravimetric method, rubidium is determined as Rb₂Na[Co(NO₂)₆].H₂O without separating uranium with a precision of the order of ±0.5%. In the XRF method, the concentration ratio of rubidium to uranium, C_Rb/C_U, is determined in the solid samples by the binary ratio method using calibration between intensity ratios (I_Rb/I_U) and concentration ratios (C_Rb/C_U). The concentration of rubidium is derived using the uranium value which is known with a precision better than ±0.05%. The XRF method has a precision better than ±0.8% for rubidium determination.     

X-ray fluorescence analysis in environmental radiological surveillance using HPGe detectors

X-ray fluorescence (XRF) has been proven to be a valuable tool for determining trace quantities of heavy metals, such as uranium and lead, in different types of samples. The present paper demonstrates the applicability of XRF spectrometry to measure the concentrations of these heavy metals in samples from natural ore and soil. The values of uranium concentrations in rock from the Peña Blanca uranium ore, in Chihuahua, México, were calculated for the purpose of precertifying the rock powders samples. The comparison with other techniques, such as inductively coupled plasma atomic emission spectrometry, atomic absorption spectrometry, alpha spectrometry and electron microscopy, was used to complete the precertification process, so that the sample powders may be used as secondary standards. The source-sample-detector geometry and the incident angle are the most important factors for obtaining low detection limits. The selected system uses a ⁵⁷Co source of about 0.1 mCi to excite the K X-rays from uranium and lead. X-rays were recorded on a CANBERRA HPGe coaxial detector. The comparative results for two incident angles (90° and 180°) performed previously by other authors show that the best geometry is the backscattering geometry. In the present paper, using EGS4 code system with Monte Carlo simulation, it was possible to determine the location and distribution of background produced by the Compton edge in the optimized geometry. This procedure allowed to find the minimum detectable concentration of uranium and lead, which was experimentally calculated using standards. The possibility of performing in vivo measurements rapidly and easily, as well as the factors affecting accuracy and the minimum detectable concentration in several samples are also discussed.     

Vertical distribution of uranium concentrations and 235U/238U atom ratios in the coastal water off Aomori, Japan: A survey prior to the operation of a nuclear fuel reprocessing facility

Summary From the viewpoint of environmental radioactivity monitoring, the determination of uranium and its isotope ratio is important for identifying and assessing the environmental impact of any unexpected release from nuclear facilities. In this work, a survey was conducted to determine ²³⁸U concentrations and ²³⁵U/²³⁸U atom ratios in coastal waters off Rokkasho Village, Aomori, Japan, where several uranium-related nuclear facilities have been operating since 1992, and a newly constructed nuclear fuel reprocessing plant is scheduled to be commissioned in 2006. Seawater samples were analyzed directly after a 10-fold dilution using isotope dilution sector-field ICP-MS. Based on the results, we concluded that there is no observable uranium contamination in the investigated sites. In addition, for the first time, a correlation between uranium concentration and salinity was established in coastal waters using the SF-ICP-MS technique.     

238U and 222Rn activity concentrations and total radioactivity levels in lake waters

The concentrations and distributions of natural radioactivity, uranium and radon in lake waters from around Van, Turkey were investigated with an aim of evaluating the environmental radioactivity. Fourteen lake waters were collected from different six lakes around Van (Turkey) to determine ²³⁸U, ²²²Rn and total alpha and total beta distributions in 2009. The total α and total β activities were counted by using α/β counter of the multi-detector low background system (PIC-MPC-9604) and the ²³⁸U concentrations were determined by inductively coupled plasma-mass spectrometry (Thermo Scientific Element 2) and radon concentrations were measured with the solid state nuclear track detector technique. The activity concentrations ranging from ND to 0.039 Bq L^?1 and from 0.026 to 3.728 Bq L^?1 for total alpha and beta, respectively, and uranium concentrations ranging from 0.083 to 3.078 μg L^?1, and radon concentrations varying between 47.80 and 354.86 Bq m^?3 were observed in the lake waters.     

An automatic spectrophotometric method for the determination of uranium(VI) extracted into a liquid ion-exchanger medium

An earlier procedure based on 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol is adapted for use with a Technicon AutoAnalyzer; 60 samples per hour can be analyzed. The range is 0.2–3 g of uranium per litre of extract. The method is readily modified for the determination of uranium (?200 μg l^-1) in ground waters.     

Determination of227Ac in geological materials through neutron activation and alpha-spectrometric assay of induced228Th

A new route has been developed for the micro-determination of²²⁷Ac in geological materials by neutron activation. The method is based on intense neutron irradiation of the analysed samples followed by separation and α-spectrometric determination of²²⁸Th, the β-decay product of the 6.1 hrs²²⁸Ac isotope formed. Two alternatives are considered for analysis related to the origin of the analysed matrix. The high sensitivity of the method is documented by the determination of 10^?17 g²²⁷Ac/g sample. The method is successfully applied for age determination of five uranium containing materials and old uranium glass from Bohemia, CSSR.