Determination Of Thorium Research Articles

Determination of uranium and thorium in apatite minerals by inductively coupled plasma atomic emission spectrometry with solvent extraction separation into diisobutyl ketone

Determination of the actinide elements (uranium and thorium) in apatite minerals has been examined by inductively coupled plasma atomic emission spectrometry (ICP-AES) with solvent extraction separation. The spectral interference by calcium in the apatite and the negative interference by the macro-component (calcium phosphate) occurred simultaneously for uranium and thorium. Therefore, after apatite mineral was treated with hot concentrated nitric acid, uranium and thorium were separated from calcium phosphate by the solvent extraction method. 1-Phenyl-3-methyl-4-trifluoroacetyl-5-pyrazolone (HPMTFP, p K a=2.56) was used as an extraction reagent in the present study. Diisobutyl ketone was selected as the extraction organic solvent. Uranium and thorium were quantitatively extracted over pH 2, and could be separated from the apatite composites. The organic phase was injected directly into the ICP-AES spectrometer. The uranium and thorium contents in apatite minerals from Florida, USA, were found to be 103±2.2 and 8.84±0.19 ppm. These results were quite comparable with those measured with ICP-mass spectrometry (ICP-MS).

Determination of thorium in environmental and workplace materials by ICP–MS

The paper outlines the advantages of the use of Inductively Coupled Plasma Mass Spectrometry (ICP–MS) over radiometric techniques to measure natural thorium, 232Th. Experimental parameters that must be taken into account in the sample digestion, preparation and ICP–MS analysis of environmental (soils, rocks, sediments) or workplace (thorium oxide, reference solutions) materials are described. The methods presented are applied to various reference materials, with the aim of providing suitable procedures to be useful for other important thorium containing materials (such as monazite sands or welding electrodes). The participation in a European Commission intercomparison exercise is detailed and a comparison with alpha spectrometry is made.

Sequential method for the determination of uranium, thorium and 226Ra by liquid scintillation alpha spectrometry

A new procedure for the determination of uranium, thorium and 226Ra from the same aliquot of an aqueous sample using extractant scintillators and liquid scintillation alpha spectrometry is proposed. The procedure is designed such that the same aqueous phase can be used in all the stages, with slight modifications. The procedure is thus very simple, requiring little manipulation of the sample. Testing of the procedure was performed obtaining satisfactory results and high reproducibility.

Determination of thorium and uranium in activated concrete by inductively coupled plasma mass spectrometry after anion-exchange separation

A sensitive analytical method was established for the determination of Th and U in activated concrete samples. The method combines an anion-exchange separation step with an ICP-MS determination technique. In the ICP-MS measurement, a few μg mL–1 of Al and Ca, a few ng mL–1 of Mn, La, Ce, Nd and Pb and pg mL–1 amounts of Li, Zr, Nb and Ba coexisting in the anion-exchange fraction of Th and U did not interfere. No adverse interference effects were observed in real sample analyses. The obtained detection limits (3σ, n = 10) of Th and U were 2.3 and 1.8 pg mL–1, respectively. The analytical precisions for ca. 5 μg g–1 Th and ca. 1 μg g–1 U in real activated concrete samples were equally less than 7% RSD. The accuracies obtained by the analysis of GSJ rock standard samples were –18.1 to 0.4% for the Th determination and –14.0 to –5.7% for the U determination. The method uses the conventional absolute calibration curve. The internal standard calibration is unnecessary.

Sequential Isotopic Determination of Strontium, Thorium, Plutonium, Uranium, and Americium in Bioassay Samples

A procedure is presented to provide sequential determination of isotopic strontium, thorium, plutonium, uranium, and americium in a single biological sample. The method begins with digestion and dissolution of the sample. Tracers and/or carriers are added to the sample for the purpose of chemical yield monitoring. Strontium is first separated from the actinides and from most of the interfering constituents of the sample by precipitation as carbonates. Strontium isotopes are purified, and 89Sr and 90Sr are measured by gas proportional counting. Actinides are separated and purified by ion exchange chromatography, co-precipitated with neodymium fluoride, filtered, and counted by alpha-particle spectrometry.

Separation of Thorium(IV) from Associated Elements Using Poly-(Dibenzo-18-Crown-6) and Column Chromatography from Picric Acid Medium

A simple column chromatographic method has been developed for the separation of thorium(IV) from associated elements using poly-(dibenzo-18-crown-6). The separations are carried out from picric acid medium. The adsorption of thorium(IV) was quantitative from 0.0005–0.05M picric acid. Amongst the various eluents tested, 2.0–8.0M HCl, HBr, 1.0–6.0M HClO4 and 5.0M acetic acid were found to be particularly efficient for the quantitative elution of thorium(IV). The capacity of poly-(dibenzo-18-crown-6) for thorium(IV) was found to be 1.29±0.01 mmol/g of crown polymer. Thorium(IV) was separated from a number of cations in binary mixtures in which most of the cations showed a very high tolerance limit. It was possible to separate thorium(IV) from a number of cations such as lanthanum(III), yttrium(III), uranium(VI), beryllium(II) and barium(II) in multicomponent mixtures. The method was extended to the determination of thorium in monazite sand. It is possible to separate and determine 5 ppm of thorium(IV) by this method. The method is very simple, rapid, selective and has good reproducibility (approximately ±2%).

Determination of Thorium in Organs from Thorotrast Patients by Inductively Coupled Plasma Mass Spectroscopy and X-Ray Fluorescence

Concentrations of thorium were determined by inductively coupled plasma mass spectroscopy in various organs collected from Japanese Thorotrast autopsy subjects to provide information on dosimetry for Thorotrast patients. Duplicate analyses were performed for 98 samples, and data for thorium in 27 different organs were obtained. The highest thorium level was found in spleen (mean: 16,000 microgram/g wet weight), followed by liver (2100 microgram/g wet weight) and bone marrow (600 microgram/g wet weight). The other concentrations decreased in the following order: lymph node, gallbladder, testis, lung, small intestine, adrenal gland, pancreas, dura, esophagus, muscle, thyroid, large intestine, stomach, fat, kidney, urinary bladder, main artery, prostate, diaphragm, trachea, heart, cerebellum, cerebrum and intervertebral disk. The last four organs showed markedly low concentrations of 2-7 microgram/g wet weight. Compared to the background thorium levels reported in the literature for human organs, the values for the organs from Thorotrast patients (even in the organs with the lowest concentrations) were at least several thousand times higher, suggesting the importance of also considering organs with minor deposition in dosimetry. Distributions of thorium in some selected organs were studied by microbeam X-ray fluorescence. The thorium conglomerates could be identified, and images of microdistributions of thorium in the organ slices were obtained.

Anion-exchange separation and determination of thorium and uranium in Eskişehir-Beylikahir ore in Turkey

Eskisehir-Beylikahir ore contains rare earth elements (REE) and thorium as bastnaesite mixed with barite, calcite and fluorite and small amounts of uranium. The mineralogical composition and Th, U, REE contents of the ore samples taken from different sectors of the same region show important variations. For the spectrophotometric determination of Th and U in the ore, successive anion-exchange and solvent extraction procedures are carried out to separate U and Th from each other and from accompanying interfering elements. The accuracy and precision of the method is demonstrated by intercomparison of the thorium standard reference samples S-14, S-15 and S-16 of IAEA. In all cases very good agreement was obtained.

Synthesis of 2-hydroxy-3-carboxyl-5-sulfonicarsenazo and its application to the spectrophotometric determination of thorium

A new highly selective and sensitive chromogenic reagent, 2-hydroxy-3-carboxyl-5-sulfonicarsenazo (ASA-HCS),was synthesized and studied for determination of trace thorium. In a high concentration nitric acid medium, thorium reacts with ASA-HCS to form a 1∶2 green complex which has a sensitive absorption peak at 676 nm. A 0–0.6 µg ml–1 concentration of thorium obeys Beer’s law. The complex is formed instantly in nitric acid medium and remains stable for 48 h at least. The stability constant of the complex is 9.76 × 1021at 25 °C, its molar absorptivity and Sandell’s sensitivity are 1.05 × 105 l mol–1 cm–1 and 0.00223 µg cm–2, respectively. Its limit of quantification, limit of detection and relative standard deviations were found to be 14.3 ng ml–1, 4.9 ng ml–1 and 1.2%, respectively. Ca(II), Mg(II), Ag(I), Al(III), K(I), Fe(III), Co(II), Ni(II), Pb(II) , Mn(II), W(VI), Cr(III), Zn(II), Cu(II), Y(III), Mo(VI), Ce(III) and U(VI) do not interfere with the determination of thorium, so the selectivity is advantageous compared with other published reagents. The stepwise dissociation constants of the reagent at λ = 554 nm and λ = 650 nm have been determined. The proposed method has been applied to the determination of thorium in waste water and rare earth–magnesium–silicon alloy with satisfactory results.

Determination of uranium and thorium in geological materials using extraction chromatography

A procedure has been developed for the determination of uranium and thorium in geological samples using extraction chromatography. Following sample preparation, uranium and thorium are pre-concentrated by precipitation with iron(III) hydroxide and then separated using UTEVA resin. The separated uranium and thorium are electrodeposited onto stainless-steel discs and then measured by alpha spectrometry. The procedure was evaluated using uraninite ore, coral and granite reference materials. The uranium and thorium concentrations and the 234U/238U and 230Th/234U activity ratio values determined for the reference materials were in good agreement with the certified values. The presence of plutonium was found to interfere with the separation, but the inclusion of a reduction step using iron(II) sulfamate eliminated the problem. Chemical recoveries for the procedure are similar to those for an anion-exchange procedure, but the extraction-chromatography procedure provides a more rapid separation using less reagents.

Determination of natural uranium and thorium in environmental samples by ETV-ICP-MS after matrix removal by on-line solid phase extraction

An on-line solid phase extraction method has been developed for the determination of 238 U and 232 Th biological certified reference material using inductively coupled plasma mass spectrometry (ICP-MS). Absolute detection limits were 2.7 pg and 3.1 pg for the determination of 238 U and 232 Th respectively, both being blank limited. The result for the determination of 238 U in NASS-4 Open Ocean Sea Water was 2.13±0.28 ng ml –1 compared with a certified value of 2.68±0.12 ng ml –1 . The results for the determination of 238 U in SLRS-3 River Water was 0.043±0.002 ng ml –1 compared with an indicative value of 0.045 ng ml –1 . Results for the determination of 238 U and 232 Th in NIST 1575 Pine Needles were 14.6±3.4 ng g –1 and 28.3±4.5 ng g –1 respectively compared with certified values of 20±4 ng g –1 and 37±3 ng g –1 , using a dry and wet ashing sample preparation method. Results for the determination of 238 U and 232 Th in NIST 1566a oyster tissue were 121±21 ng g –1 and 29±8 ng g –1 for 238 U and 232 Th compared to certified and indicative values of 132±12 ng g –1 and 40 ng g –1 , using the same method. When a lithium metaborate fusion method was used, results for 238 U and 232 Th were 23.3±2.0 ng g –1 and 36.2±5.6 ng g –1 respectively in NIST 1575 Pine Needles. The application of electrothermal vaporisation ICP-MS (ETV-ICP-MS) to NASS-4 Open Ocean Sea Water gave 2.81±0.54 ng ml –1 and SLRS-3 River Water 0.045±0.004 ng ml –1 for 238 U. When the fused NIST 1575 samples were analysed using ETV-ICP-MS, results for 238 U and 232 Th were 19.5±1.7 ng g –1 and 38.8±2.2 ng g –1 respectively. Absolute detection limits for ETV-ICP-MS were 30 fg and 9 fg for 238 U and 232 Th respectively, both being blank limited.

Thorium: Determination by CDTN, Brazil

One of the tasks of the Radiochemical Sector, CDTN/CNEN, Brazil, is to meet the clients' analytical needs. The Sector has been facing the challenges of determining several elements in diversified matrixes from all over the country since the sixties. It has been giving analytical support to universities, industries, environmental monitoring programs, research institutes. Due to the growing need to determine thorium isotopes through the years it was necessary to work out a routine procedures. Nowadays the determination of thorium consists of a well established routine whose procedures are applied to grouped samples according to their kind, physical state, matrix interference, detection limits and number of samples. This paper describes the methods used by CDTN to determine232Th by neutron activation analysis and230Th and228Th by radiochemical separations and alpha spectrometry in several matrixes.

The limit of detection improvement in TLC determination of uranium and thorium in the presence of other metal ions

The limit of detection (LOD) improvement in TLC determination of uranium and thorium in presence of other metal ions is presented in this paper. The mobile phase system contains iso-propyldithiophosphotic acid (i-PrDTP), as a complexing agent, in order to differentiate the studied species by modifying their retention. The paper reports the successful separation and the quantitative determination of uranium and thorium in the presence of other metal ions in the concentration range 2.5–30 μg/μl.

Separation and quantitative determination of dioxouranium(VI) and thorium(IV) ions in the presence of different metallic ions by TLC using iso-propyldithiophosphoric acid as complexing agent

Abstract The separation of uranium and thorium from matrices containing various metal ions, was studied. The mobile phase contains isopropyldithiophosphoric acid (i-PrDTP), as a complexing agent, in order to differentiate the studied species by modifying their retention. The paper reports the successful separation and the quantitative determination of uranium and thorium in the presence of Ni2+, Co2+ and Ag+ in the concentration range 2.5–2.5 μg/μl for uranium and 2.5–30 μg/μl for thorium.

Spectrophotometric and complexometric methods for the determination of thorium and fluoride using bromocresol orange reagent

The ternary purple coloured complex formed between Th 4+, bromocresol orange (BCO) and cetylpyridinium bromide (CPB) in acidic medium was investigated spectrophotometrically. Results obtained revealed the formation of 1:1:1, Th:BCO:CPB complex in aqueous solution at pH≈0.5 with a logarithmic conditional stability constant of 12.04±0.1, I=0.1 at 25°C. The colour of the ternary complex was used for the determination of thorium(IV) in the range of 0.02–2.6 μg ml −1 Th 4+, ϵ=9.2×10 4 l mol −1 cm −1 at 560 nm. Beside its high sensitivity, the reaction was also proved to be highly selective for Th 4+. Thorium(IV) was determined in presence of great number of transition metal ions, rare earths and different anions. Th 4+ was also determined with high accuracy and precision by its titration with disodium ethylenediaminetetraacetate (Na 2EDTA) using BCO as an indicator at pH≈0.5. The endpoint was detected either visually or spectrophotometrically ( λ=550 nm). The proposed procedures were successfully applied for the determination of Th 4+ in standard Th-U ores and in a series of naturally occurring ores or minerals containing thorium. A spectrophotometric method was also described for the determination of fluoride ion, which was based upon the decrease in colour intensity of the Th-BCO complex on mixing it with F − ion. The proposed method was convenient, rapid and sensitive for fluoride. It could be used for the determination of fluoride ion in the 0.02–3.00 μg ml −1 range (S.D.±0.9%). The proposed method was successfully applied for direct determination of F − ion in water obtained from different origins and the results were satisfactory.

Separation and determination of thorium, uranium and mixed rare-earth elements as their UV/Vis absorbing complexes by capillary zone electrophoresis

Separation and determination of thorium, uranium and mixed rare-earth elements (RE) as their 2-(2-arsenophenylazo)-1,8-dihydroxyl-7-(4-chloro-2,6-dibromophenylazo)-naphthalene-3,6-disulfonic acid (DBC-As) complexes by capillary electrophoresis is presented in this paper. The pre-column derivitization conditions are discussed. Some separation parameters such as pH value, type of carrier electrolyte, applied voltage, the concentration of ligand in buffer and the sample size are also optimized. Under the selected conditions, the complete separation of thorium and uranium from mixed RE was accomplished in 10 min. Quantitative analyses exhibited an excellent linear dynamic relationship in the range of over two orders of magnitude. Detection limits of 4.81×10 −8, 7.23×10 −8, and 59.4×10 −8 mol l −1 for RE, Th and U were obtained, respectively. This method was applied to the determination of these metal ions in ore samples.

Determination of isotopic thorium in biological samples by combined alpha-spectrometry and neutron activation analysis

The determination of isotopic thorium by alpha-spectrometric methods is a routine practice for bioassay and environmental measurement programs. Alpha-spectrometry has excellent detection limits (by mass) for all isotopes of thorium except232Th due to its extremely long half-life. This paper reports a pre-concentration neutron activation analysis (PCNAA) method for232Th that may be performed following alpha-spectrometry if a suitable source preparation material is utilized. Human tissues and other samples were spiked with229Th and the thorium was isolated from the sample using ion exchange chromatography. The thorium was then electrodeposited from a sulfate-based medium onto a vanadium planchet, counted by alpha-spectrometry, and then analyzed for232Th by neutron activation analysis. The radiochemical yield was determined from the alpha-spectrometric method. Detection limits for232Th by this PCNAA method are approximately 50 times lower than achieved by alphaspectrometry.

Pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues by extraction chromatography

An extraction chromatographic method is described for the pre-concentration and separation of thorium, uranium, plutonium and americium in human soft tissues. Tissues such as lung and liver are oven dried at 120°C, ashed at 450°C and the ashed sample is alternately wet (HNO3/H2O2) and dry ashed, and then dissolved in 8M HCl. Because of the complex matrix and large sample samples (up to 1500 g), the actinides were preconcentrated from the tissue solution using the TRUTM resin (EIChroM) prior to elemental separation by extraction chromatography and determination of americium, plutonium, uranium and thorium by alpha spectrometry. The actinides were eluted from the preconcentration column and each actinide was individually eluted on TEVATM and TRUTM resin columns in a tandem configuration. Actinide activities were then determined by alpha spectrometry after electrodeposition from a sulfate medium. The method was validated by analyzing human tissue samples previously analyzed for americium, plutonium, uranium and thorium in the United States Transuranium and Uranium Registries (USTUR). Two National Institute of Standards and Technology (NIST) Standard Reference Materials, SRM 4351-Human Lung and SRM 4352-Human Liver were also analyzed.

Extraction studies of uranium(VI) and thorium(IV) with tributylphosphine oxide

Tributylphosphine oxide is proposed as an extractant for uranium(VI) and thorium(IV) from salicylate media. The optimum extraction conditions were evaluated by studying various parameters such as pH, sodium salicylate concentration, tributylphosphine oxide concentration, diluents and shaking time. The extracted species were ascertained by logD-logC plots. The method is simple, fast, precise and permits the separation of uranium(VI) and thorium(IV) in binary as well as multicomponent systems. The method is also applied for the determination of uranium(VI) and thorium(IV) in monazite sand samples.

A preliminary investigation on the determination of lanthanoids, thorium and uranium in brine and deposit of a salt lake in China

A brine sample and two deposit samples of a salt lake in China were analyzed for their contents of lanthanoids (Ln's), thorium and uranium by neutron activation analysis. Five Ln's were determined at sub ppb levels. Th and U contents were at about the same levels as those of Ln's. The lanthanoid abundance patterns (Ln pattern) of the three samples are similar to each other, each having a negative slope in the light Ln region. There seems no substantial difference in distribution between the solution (brine) and solid (deposit) phases among Ln's.