A titrimetric method for the sequential determination of thorium and uranium

A method for the sequential determination of thorium and uranium has been developed. In the sample solution containing thorium and uranium, thorium is first determined by complexometric titration with ethylenediaminetetraacetic acid (EDTA) and then in the same solution uranium is determined by redox titration employing potentiometry. As EDTA interferes in uranium determination giving positive bias, it is destroyed by fuming with HClO₄ prior to the determination of uranium. A precision and accuracy of better than ±0.15% is obtained for thorium at 10mg level and uranium ranging from 5 mg to 20 mg in the aliquot.     

Determination of traces of free acid in uranyl salt solutions

A method for the determination of free acid in the presence of uranium(VI) is suggested. It involves the extraction of uranium by TBP from a solution saturated with potassium nitrate or chioride in order to prevent interference from the hydrolysis of uranium. The end-point is detected potentiometrically at pH 3.4. The method is suitable for the determination of 0.1–1.5 millimoles of acid in the presence of as much as 1.0 millimole of uranium.     

Use of diethazine hydrochloride for the extractive spectrophotometric determination of uranium and as a redox indicator

Optimum conditions have been established for the formation and extraction of the complex formed from diethazine, thiocyanate and uranium(VI). An extractive spectrophotometric method for the determination of uranium(VI) is described. Experimental conditions have been also established for the direct titrimetric determination of uranium(IV) with potassium dichromate, using diethazine hydrochloride as redox indicator. Interferences have been considered.     

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

Summary 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.     

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.     

Spectrophotometric method for the direct determination of uranium in carbonate solution

Summary A spectrophotometric method for direct determination of uranium in carbonate solution has been developed. No extraction or decomposition steps are necessary. The highly sensitive (4-2-pyridylazo) resorcinol, as well as 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol, producing very stable uranium(VI) complexes, were used for its spectrophotometric determination.The usefulness of the proposed methods was examined by determination of uranium in real samples from a wet-process phosphoric acid estimation of uranium.     

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.     

Assay for oxygen in uranium in the 0.1–1.0 wt% range using 14-MeV neutron activation

The X-ray spectrometric method for uranium determination in sea water is discussed. Two techniques of uranium enrichment are presented: (1) precipitation with the chelating agent ammonium-1-pyrrolidine dithiocarbamate (APDC) in the presence of iron(II) as a carrier and (2) complexation with APDC followed by adsorption on activated carbon. The best pH range and the other optimized conditions for uranium determination in sea water with both methods are reported.     

Individual determination of uranium and plutonium in a single aliquot

Studies on the individual potentiometric determination of uranium and plutonium in a single aliquot have been initiated recently in our laboratory. It was required to adapt the reported procedures (for the precise determination of uranium and plutonium individually when present together in a sample) at various stages to make them suitable for the successive application of the procedures to the same aliquot. Two alternative schemes are proposed in the present work. In the first, plutonium is determined by HClO₄ oxidation followed by the determination of total uranium and plutonium by Zn(Hg) reduction. In the second, plutonium is determined by AgO oxidation following the determination of total uranium and plutonium by Zn(Hg) reduction. Amount of uranium is computed in both cases from the difference of two determinations. Precision for the assay of plutonium and uranium was found to be ±0.25% and ±0.35%, respectively, at milligram levels.     

Coulometric determination of uranium and iron or plutonium in a single aliquot using platinum working electrode

A controlled potential coulometric method developed earlier for the determination of uranium in the presence of iron or plutonium using platinum working electrode was extended for individual determination of uranium and iron or plutonium in single aliquot. After uranium determination, Fe(III) or Pu(IV) in the aliquot is reduced electrolytically to Fe(II) or Pu(III) and subsequently determined by electrolytic oxidation to Fe(III) or Pu(IV), respectively. Analysis of synthetic solutions indicated that the values for uranium, iron and plutonium obtained by this method are reproducible within±0.2% and are in good agreement with values obtained using conventional redox methods 1, 2.     

Potentiometric determination of uranium in phosphate-perchlorate medium and its applicability in the natural uranium fuel cycle

A potentiometric method has been developed for the determination of uranium in phosphate-perchlorate medium. A significant feature of this method is its applicability for the determination of uranium in uranium-bearing CaF₂ slags and fused salt cakes generated at the natural uranium conversion and fabrication plants, respectively. These uraniumbearing slags and cakes contain large amounts of calcium and barium, respectively, where the conventional Davies-Gray and the related methods cannot be applied. A distinct advantage of the present method over coulometric determination of uranium in perchloric acid medium is that it can easily be adopted for routine analysis.     

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.     

Sorption-spectrometric determination of thorium(IV) and uranium(VI) with the reagent Arsenazo III on the solid phase of a fibrous material filled with a cation exchanger

The possibility of the use of organic reagents of the Arsenazo III group for the sorption-spectrometric determination of elements on fibrous cation-exchange materials was examined. The conditions of the sorption of Arsenazo III with the use of diphenylguanidinium chloride on the strongly acidic fibrous cation exchanger PANV-KU-2 were found. Procedures for the determination on the solid phase were developed for thorium in 7 M HNO₃ in the presence of 30-fold amounts of uranium with the detection limit of thorium of 0.005 μg/mL and for uranium in 0.05 M HCl in the presence of fivefold amounts of thorium with a detection limit of uranium of 0.05 μg/mL. The conditions were found for the selective preconcentration of thorium and uranium in the presence of each other, and a procedure was developed for their separate sorption-spectrometric determination.     

Bestimmung der freien Säure in wäßrigen Uran(IV)-nitrat- und Uran(IV)-perchloratlösungen

Methods described in literature for the determination of free acid in solutions containing plutonium(IV), uranium(VI) and aluminium(III) were investigated for their applicability in the presence of uranium(IV). Most methods turned out to work in the presence of uranium(IV). The simplest procedure was the suppression of the uranium(IV) hydrolysis by complexation with excess of fluoride. No bias was observed in the presence of 0–30 mg of uranium(IV). A variance of 1.4% resulted from the determination of 0.4 millimole of acid in the presence of 26 mg of uranium(IV) and a variance of 0.26% was obtained when 2 millimoles of acid were determined in the presence of 130 mg of uranium(IV). Uranium(IV) from 30–260 mg in 250 ml caused a negative bias, which can be corrected for. — A concentration of potassium fluoride in the titration medium of 10 g/l turned out to be optimum. In 11/2 years more than 750 determinations were carried out with the same glass electrode and no destruction of the electrode was observed. The influence of uranium(VI), iron(III) and aluminium (III) on the determination of the free acid was also investigated.     

Colorimetric uranium determination with arsenazo

A rapid and sensitive method is described for the quantitative colorimetric determination of uranium(Vl). Masking agents such as EDTA, tartaric acid or thioglycerol make possible the determination of uranium in the presence of many foreign metal ions. If thorium is present, a preliminary extraction of uranium as the diethyldithiocarbamate is required.     

Determination of micro amounts of uranium by a molybdenum blue method

A new and highly sensitive spectrophotometric method has been developed for the determination of micro amounts of uranium by a molybdenum blue method. The method is based on the observation that at low acidities uranium(IV) reduces ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of uranium present. The variables affecting development of the colour have been investigated and the conditions optimized. Beer's law is found to hold good for uranium concentrations between 1 and 20 ppm, with a precision of 2%. The effect of diverse ions has been studied. The method is useful for the determination of uranium present as an impurity (down to 0.1%) in plutonium, neptunium or thorium.     

Determination of uranium by fluorescence method

The paper describes a procedure for the determination of uranium in dilute solutions by fluorescence method. Factors influencing the determination in a phosphoric acid medium were studied. The detection limit of uranium determination is 0.04–0.05 ppm.     

Indirect determination of uranium by the on-line reduction and fluorimetric detection of cerium(III).

A novel flow injection method has been developed for the indirect determination of uranium by the on-line reduction and subsequent fluorimetric detection of cerium(III). A sample solution containing uranium(VI), prepared as a sulfuric acid solution, was injected into a sulfuric acid carrier solution and passed through a column packed with metal bismuth to reduce uranium(VI) to uranium(IV). The sample solution was merged with a cerium(IV) solution to oxidize uranium(IV) to uranium(VI) and the cerium(III) generated was then monitored fluorimetricaly. The present method is free from interference from zirconium, lanthanides, and thorium, and has been successfully applied to the determination of uranium in monazite coupled with an anion-exchange separation in a sulfuric acid medium to eliminate iron(III). The sample throughput was 25 per hour and the lowest detectable concentration was 0.0042 mg l(-1).     

激光-时间分辨荧光法测定U3O8中痕量硼

本文提出了一种测定U3O8中痕量硼的激光-时间分辨荧光法, 在适当介质中, 用小型氮分子激光器激发硼与二苯甲酰基甲烷配合物的荧光, 发现此配合物的荧光寿命为2ms, 它比铀的荧光寿命长得多, 从而可将荧光的时间分辨技术应用于铀中硼的测定, 不经分离基体铀即可进行测定, 方法简单而快速, 检测下限达到0.02ng.mL^-^1(硼),当取样10mg铀时, 能测定0.01ppm的硼。用本法分析了含量在0.04-0.5ppm几个U3O8样品, 结果与其他方法相符。