Uranium In Geological Samples Research Articles

Comparison of neutron activation analysis techniques for the determination of uranium concentrations in geological and environmental materials

We have described the determination of uranium in environmental, geological, and agricultural specimens by three different non-destructive nuclear methods. The effectiveness, as defined as the lower limits of detection in this work, of quantifying trace levels of bulk uranium in geological samples was evaluated for several common NAA techniques. These techniques include short-lived and medium-lived neutron activation analysis using thermal and epithermal neutrons; these results were compared with an assessment of Compton suppressed gamma-ray counting. A careful evaluation of three major (n,γ) reactions with chlorine, manganese and sodium that could impede determining low levels of uranium due to high Compton continuums was done. The evaluation of Compton suppressed passive gamma counting revealed that uranium concentrations below 50 mg kg−1 were not adequate to achieve good counting statistics using the 234mPa the second daughter product of 238U.

Column chromatographic separation of uranium(VI) and other elements using poly(dibenzo-18-crown-6) and ascorbic acid medium

A selective and very effective separation method for uranium(VI) has been developed by using poly(dibenzo-18-crown-6) and column chromatography. The separations are carried out from ascorbic acid medium. The adsorption of uranium(VI) was quantitative from 0.00002 to 0.006 M ascorbic acid. The elution of uranium(VI) was quantitative with 2.0–8.0 M HCl and 2.0–5.0 M H 2SO 4. The capacity of poly(dibenzo-18-crown-6) for uranium(VI) was found to be 0.92±0.01 mmol g −1 of crown polymer. Uranium(VI) was separated from a number of cations in binary as well as in multicomponent mixtures. The method was extended to the determination of uranium in geological samples. It is possible to separate and determine 5 ppm of uranium(VI) by this method. The method is very simple, rapid, selective and has good reproducibility (approximately ±2%).

Comparison of uranium determination in some Syrian geologic samples using three reactor based methods

A set of 25 samples of soil, sediments, carbonate and phosphate rocks from Syria were analysed for uranium, using three reactor based methods; instrumental neutron activation analysis (INAA), delayed neutron counting (DNC) and one cycle of irradiation utilizing the cyclic activation system (CAS). Although the three methods are capable of irradiation samples, the last method is the least established for U determination in rocks. The measurements obtained by the three methods are compared. The results show good agreement, with a distinct linear relationship and significant positive correlation coefficients. It was concluded that the CAS method could reliably be used to rapidly determine uranium in geological samples.

Liquid-liquid extraction separation of uranium(VI) from associated elements using dibenzo-24-crown-8 from hydrobromic acid medium

Liquid-liquid extraction of uranium (VI) from hydrobromic acid solutions with dibenzo-24-crown-8 in nitrobenzene have been investigated. Uranium(VI) was quantitatively extracted from 6.0–8.0M hydrobromic acid with 0.001–0.01M dibenzo-24-crown-8 and was quantitatively stripped from the organic phase with 0.1–1.0M hydrochloric acid, 0.5–10M nitric acid, 2–10M perchloric acid, 3.0–10M sulfuric acid or 3.0–10M acetic acid. It was possible to separate uranium(VI) from a number of elements in binary mixtures. Most of the elements showed very high tolerance limit Uranium(VI) was also separated from a number of associated elements in multicomponent mixtures. The method is very simple, selective, rapid and highly reproducible (approximately±2%) and was applied to the analysis of uranium in geological samples.

Flow‐injection in‐valve solid‐phase extraction spectrophotometric determination of uranium in geological samples

Flow-injection analysis (FIA) system incorporating in-valve solid-phase extraction microcolumn for on-line separation and preconcentration using a new resin, U/TEVA.Spec™, has been proposed for the spectrophotometric determination of uranium in geological samples using 4-(2-pyridylazo) resorcinol (PAR) as a color agent. Optimization of the condition involved in the system was investigated. Possibility of a single standard calibration is discussed. © 1998 John Wiley & Sons, Inc. Lab Robotics and Automation 10: 25–31, 1998

Flow-injection in-valve solid-phase extraction spectrophotometric determination of uranium in geological samples

Flow-injection in-valve solid-phase extraction spectrophotometric determination of uranium in geological samples

5-(2′-Carboxyphenyl)azo-8-quinolinol as a sensitive reagent for extractive spectrophotometric determination of uranium in geological samples

A new sensitive extractive spectrophotometric method has been suggested for the determination of uranium in soils, stream sediments and rock samples using 5-(2′-carboxyphenyl)azo-8-quinolinol (R). Uranyl nitrate is extracted in isobutylmethyl ketone (MIBK) at pH 5.2–6.1 in presence of saturated ammonium nitrate solution. The aqueous solution of R is shaken with MIBK containing uranyl nitrate. R forms almost instantaneously an amber coloured complex with the uranium in MIBK. The complex is stable for 24 hours. The molar absorptivity and Sandell's sensitivity of the complex are 1.035·104l·mol−1·cm−1 and 0.022 μg·cm−2, respectively, at λmax 524nm. Beer's law is obeyed over the range 1.4–7.1 μg·ml−1 of uranium. An amount as low as 1.4 μg·ml−1 of the uranium could be satisfactorily determined within a relative standard deviation of ±1.7%. The proposed method is sensitive, highly precise, simple in operation, rapid and reliable.

Solvent extraction separation of uranium(VI) with dibenzo-24-crown-8

Uranium(VI) was quantitatively extracted with 0.01M DB-24-crown-8 in nitrobenzene from 6 to 10M hydrochloric acid. From the organic phase uranium was stripped with 2M nitric acid and determined spectrophotometrically with PAR at 530 nm. Uranium(VI) was separated from a large number of elements in binary mixtures as well as from multicomponent mixtures. The method was extended to the analysis of uranium in geological samples and animal bone.

Extraction Spectrophotometric Method for the Determination of Uranium in Geological Samples Using a Ternary Complex of 2-(p-Methylphenylazo)pyridine and Thiocyanate

An uranyl ion (UO22+) reacts with 2-(p-methylphenylazo)pyridine in thiocyanate system. The species is extractable quantitatively into methyl isobutyl ketone (MIBK) in the presence of nitrate ion, showing an absorption maximum at 370nm. Beer′s law is obeyed over the range 0.15-1.5μg of uranium/ml. The molar absorptivity and Sandell′s sensitivity are 0.166×104 l mol-1 cm-1 (on the basis of uranium content) and 0.0014μg/cm2, respectively. Various international geochemical reference samples were chosen to check the validity of the method. The results obtained were in good agreement with the published data.

Application of two-tracer isotope dilution mass spectrometry in the determination of uranium in geological samples

The determination of the uranium concentration in mineral samples using two tracer (233U and 235U) mass spectrometric isotope dilution techniques is described. The precision and accuracy are discussed and results are compared with those obtained by x-ray fluorescence and instrumental neutron activation methods. Based on the two independent values obtained for the same dilution, parameters such as the chemical procedures adopted, effect of mass fractionation and uranium distribution in minerals are evaluated. The ability of the method to distinguish between the analytical errors and heterogeneous distribution of uranium is discussed.

Isotope dilution alpha spectrometry with spike enriched in233U for the determination of uranium in geological samples

Isotope dilution alpha spectrometric /IDAS/ method has been developed for the determination of uranium in geological materials. The spike employed as uranium enriched in the isotope 233. The results of the analysis for rock and ore samples show that the precision and accuracy of the method are comparable to other analytical techniques and the method can be employed for routine analysis.

Spectrophotometric determination of trace uranium in geological samples by flow injection analysis with on-line levextrel resin separation and preconcentration

A flow-injection system with on-line separation and preconcentration is described for the spectrophotometric determination of trace uranium in geological samples. Uranium is selctively adsorbed from 0.7 mol l −1 nitric acid on a microcolumn (40 mm long, 4.4 mm i.d.) containing levextrel CL-5209 resin (120–200 mesh) and separated from the sample matrix and most of the co-existing ions; 10-fold concentration is obtained. Eluted uranium is determined spectrophotometrically with arsenazo-III. The detection limit is μg l −1 uranium and calibration is linear up to 0.3 mg l −1 uranium With dual columns operated alternately for adsorption and elution, 30 samples can be analyzed per hour. Masking agents are added to eliminate interferences from thorium and iron. The method is sensitive and highly selective, easy to operate and suitable for routine analysis of geological samples for uranium.

Some applications of uranium tracing in geological samples using thermal neutron induced fission

The mode of distribution of uranium in geological samples is closely related to the type of geochemical environment during the time of formation or alteration of a specific specimen. By high resolution micromapping of U in sediment samples from the Kaapvaal Craton, South Africa, using n-induced U-235 fission tracks in mica detectors, information is obtained about the redox potential of the hydrosphere- atmosphere system at the time of U-deposition or remobilization. Mineralogical and textural considerations as well as radioactive disequilibria in the natural U-decay series, measured by α-spectrometry, were used to identify the type of U-mobilization. The U-distribution patterns of carefully selected conglomerate samples from the Witwatersrand basin are in agreement with the assumption of a predominantly reducing Earth atmosphere at the time of basin formation some 2.6 × 10 9 y ago.

High-speed bulk analysis of uranium in geological samples by the delayed neutron method

High-speed bulk analysis of uranium in geological samples by the delayed neutron method

The determination of uranium in geological samples by an indirect atomic absorption spectrometric procedure

The determination of uranium in geological samples by an indirect atomic absorption spectrometric procedure

On the fission track method for the determination of the uranium content of whole rock samples

The induced fission track technique in conjunction with internal standard addition has been used for the determination of uranium in geological samples. Convenient aliquots of the sample solution spiked with known amounts of uranium, deposited and dried on “Lexan”, were irradiated in CIRUS (thermal flux 2·10 12 n cm -2 sec -1; irradiation time 40 min). These irradiated “Lexan” pieces were etched with 25% (w/v) sodium hydroxide for 2 min at 200° to reveal the tracks. From a count of track densities in the “Lexan”, the uranium contents of the two USGS rock standards G-2 and BCR-1 were determined to be 2.01 and 1.64 p.p.m. of uranium, respectively; these results are in good agreement with the literature values.

The determination of thorium and uranium in geological samples by an alpha-counting technique

The use of a thick-source alpha-particle detection technique for the simultaneous determination of both thorium and uranium in geological samples is discussed. The technique depends on the presence of the “thorium pairs” resulting from the successive decays of thoron and the short-lived isotope thorium A, and has been extensively employed by Mayneord and others in biophysical problems. The absolute accuracy, the sensitivity and the limitations of the method are considered. Finally, thorium and uranium determinations for the granites G—1 and Tory Hill and the diabase W—1 are presented.