Determination of natural uranium in biological samples using the solid state nuclear track detector method

For the solution of most of the problems which are connected to the biological and physiological role of natural uranium in plants and animal organisms about 10⁻¹⁴ g uranium should be determined. However most of the physico-chemical methods for the determination of natural uranium in biomaterials are time-consuming and possess considerable error. On the basis of addition and inner standard methods a version of Solid State Nuclear Track Detectors (SSNTD) method has been developed in order to determine the natural uranium in biospecimens. According to the experimental data simple relations have been obtained for the calculation of uranium concentration in biomaterial and minium uranium concentration in biosolution which can be measured by the detector used. Under irradiation of SSNTD at a thermal neutron flux of (3–5)·10¹⁵n·cm⁻² the detector sensitivity is 2.30·10⁻⁹ g U/ml for glass detectors; 9.60·10⁻¹⁰g U/ml for the detectors made from artificial mica.     

Neutron activation analysis of uranium in human bone,drinking water and daily diet

Uranium in human bone, drinking water and daily diet has been determined by neutron activation analysis using the²³⁸U(n, γ)²³⁹U reaction. An improved scheme for the separation of the²³⁹U is proposed; with this scheme, after neutron irradiation in a 100 kW TRIGA reactor, a uranium content as low as 5·10⁻¹¹ g can be determined reliably, rapidly and easily. A wide range of uranium concentrations, from about 0.1 ppb up to about 10 ppb has been found in the bones of normal Japanese. Water from several Japanese city water services, and the daily diet taken in two Japanese cities, have been found to contain an average 9·10⁻⁹ g/l and 1.5 μg per person-day uranium, respectively.     

Voltammetric study of the interaction of the ofloxacin–copper complex with DNA, and its analytical application

The electrochemical behavior of the ofloxacin–copper complex, Cu(II)L₂, at a mercury electrode, and the interaction of DNA with the complex have been investigated. The experiments indicate that the electrode reaction of Cu(II)L₂ is an irreversible surface electrochemical reaction and that the reactant is of adsorbed character. In the presence of DNA, the formation of the electrochemically non-active complexes Cu(II)L₂-DNA, results in the decrease of the peak current of Cu(II)L₂. Based on the electrochemical behavior of the Cu(II)L₂ with DNA, binding by electrostatic interaction is suggested and a new method for determining nucleic acid is proposed. Under the optimum conditions, the decrease of the peak current is in proportional to the concentration of nucleic acids in the range from 3 × 10⁻⁸ to 3 × 10⁻⁶ g · mL⁻¹ for calf thymus DNA, from 1.6 × 10⁻⁸ to 9.0 × 10⁻⁷ g · mL⁻¹ for fish sperm DNA, and from 3.3 × 10⁻⁸ to 5.5 × 10⁻⁷ g · mL⁻¹ for yeast RNA. The detection limits are 3.3 × 10⁻⁹, 6.7 × 10⁻⁹ and 8.0 × 10⁻⁹ g · mL⁻¹, respectively. The method exhibits good recovery and high sensitivity in synthetic samples and in real samples.     

Determination of noble metals by resonance neutron activation technique

Rhodium, palladium, platinum and iridium have been determined in silver matrix by nondestructive activation analysis upon activation with cadmium- and silver-filtered resonance neutrons. Experiments with different types of filter combinations are reported. The sensitivity of the method is 5·10⁻³% for rhodium, 5·10⁻³% for palladium, 3·10⁻²% for platinum and 5·10⁻³% for iridium.     

Determination of naturally occurring radionuclides in ultrapure organic liquids

For the determination of trace elements in organic liquids radiochemical neutron activation analysis has been combined with counting methods geared to various decay modes of indicator radionuclides leading to a high sensitivity required for ultrapure samples. The activation parameters such as irradiation time, sample mass and neutron flux have been enlarged to the maximum possible in the available irradiation facility. Separation yields and adsorption losses have been studied in detail for a set of elements in order to rule out losses during the separation process. The attainable limits of detection are 2 · 10^–16g/g for U and Lu, in the 5 · 10^–15g/g range for Th and Sm, in the 1 · 10^–14g/g region for La, 5 · 10^–13g/g for Rb, Cd and 2 · 10^–12g/g for K and In. Although the analysis focused on traces of naturally occurring radioisotopes, results for Cr, Fe, W and Zn are presented as well. Received: 14 May 1997 / Revised: 28 August 1997 / Accepted: 9 September 1997     

Evaluation of a single collector, double focusing sector field inductively coupled plasma mass spectrometer for the determination of U and Pu concentrations and isotopic compositions at trace level

This work explores the performance of the “Axiom”, a double focusing sector field ICP-MS (ICP-SFMS) in the determination of actinide concentration and isotopic ratio at trace level. On the actinide mass range the performances observed are characterized by high sensitivity, around 2.8·10⁶ cps·μg⁻¹·l, and low background, below 0.3 cps. Therefore, the absolute instrumental detection limit is approximately 0.05 fg for Pu isotopes. Furthermore, the ²³⁵U/²³⁸U ratio for a 0.5 μg·l⁻¹ U500 isotopic standard could now be measured using the ICP-SFMS with a relative standard deviation less than 0.1%. Moreover, the accuracy of the measured ratio was demonstrated at low concentration with the target value remaining within experimental uncertainty limits. This revised version was published online in July 2006 with corrections to the Cover Date.     

Epithermal neutron activation analysis of uranium by neptunium-239 using high resolution gamma-spectrometry

The possibility to use the most intensive gamma-peak of²³⁹Np for INAA of uranium with epithermal neutrons and high resolution Ge(Li)-spectrometry is evaluated. A way for calculation of the peak area of overlapping peaks of¹⁵³Sm and²³⁹Np is proposed. This can be used in other similar cases in the practice of NAA. On this basis a scheme for NAA of uranium in geological objects is proposed. Lower detection limit is 8·10⁻⁸ g U the precision 5–10% (relative standard deviation). The accuracy is demonstrated by the analysis of some geological standard reference materials.     

Applications of gamma-spectrometry in determining chlorine in aqueous solutions

A method is described for the radioanalytical determination of traces of chlorine in aqueous solutions without radiochemical separation or purification. Using a gamma-spectrometer with monocrystal scintillator, the sensitivity of the analysis is about 1·10⁻⁸ g of chlorine/ml, the time of analysis being 15 minutes. For the selective determination of chlorine in aqueous solutions containing a large amount of impurities, a bicrystal scintillation sum-coincidence spectrometer was employed with 120×100 mm NaI(Tl) crystals and thus the³⁸Cl cascade radiation could be used. Application of the sum-coincidence spectrometer allowed a reliable determination of 1·10⁻⁷ g of Cl/ml against a background of 1·10⁻⁵ g of Na/ml.     

Etude des possibilites de dosage du lithium par activation au moyen de protons et de deutons de moyenne energie

The determination of lithium by measuring⁷Be, produced by proton or deuteron activation, has been studied. The extent of interference from boron or beryllium, which also form⁷Be, was measured. The calculated sensitivity limits when activating for one hour with 10μA beams of 14 MeV protons or 25 MeV deuterons are, for lithium, 1·10⁻¹ and 2.5·10⁻² ppm and for boron, 2·10⁻¹ and 1·10⁻¹ ppm, respectively.      

Preparation and characterization of loess sediment for use as a reference material in the annual radiation dose determination for luminescence dating

Loess sediment was prepared and characterized with well-established K, Th and U contents, and corresponding ⁴⁰K, ²³²Th and ^235,238U activities, intended for use as a reference material in the annual radiation dose determination for luminescence dating. To this purpose, loess was collected in Volkegem, Belgium, and — after drying, pulverizing and homogenizing — characterized via k ₀-INAA and HPGe gamma-ray spectrometry. This led to 12 kg material with a grain size below 50 μm, with established K, Th and U homogeneity, with the ²³²Th and ²³⁸U decay series proven to be in equilibrium, and with the following K, Th and U reference data: K = 16.5±1.5 g·kg⁻¹ (⁴⁰K = 497±45 Bq·kg⁻¹); Th = 10.4±0.6 mg·kg⁻¹ (²³²Th = 42.2±2.5 Bq·kg⁻¹); U = 2.79±0.12 mg·kg⁻¹ (²³⁸U = 34.5±1.5 Bq·kg⁻¹; ²³⁵U = 1.59±0.09 Bq·kg⁻¹; ^235+238U = 36.1±1.7 Bq·kg⁻¹). These data were confirmed via comparison with the results from NaI(Tl) field gamma-ray spectrometry, thick-source ZnS alpha-counting and thick-source GM beta-counting (after converting all data to Gy·ka⁻¹). The reference material is available (as aliquots up to 200 g) from the Ghent Luminescence Laboratory to all interested luminescence dating laboratories upon motivated request.     

Determination of chromium in blood by neutron activation analysis

A procedure for the determination of chromium in blood has been developed with a sensitivity of 5×10⁻³ μg Cr. Dried blood was irradiated with a neutron flux of 10¹² n·cm⁻²·sec⁻¹ in the VVRS reactor for 4 weeks, then the sample was mineralized and the chromium isolated by extraction as perchromic acid. The determination of the chromium content was accomplished by measuring the 0.32 MeV gamma energy of⁵¹Cr. In order to make correction for the interfering reaction⁵⁴Fe(n,α)⁵¹Cr, the formation of chromium from high-purity iron was investigated. The chromium content of the blood samples was between 1.03×10⁻² and 5.2×10⁻² ppm Cr.     

Aktivierungsanalytische Bestimmung von Chrom und Zink in biologischem Material

An activation analysis method has been developed for the determination of chromium and zinc in biological material. After the samples had been activated in a thermal flux of 7·10¹¹ n·cm⁻²·sec⁻¹ for 100 hours, both elements were separated from interfering radionuclides by means of ion-exchange and distillation processes. Gamma spectrometry was used to measure the activities of⁵¹Cr and⁶⁵Zn. The practical limits of detection were found to be 1·10⁻⁸ g for chromium and 1·10⁻⁷ g for zinc. The results of model experiments and of the analysis of blood taken from two individuals proved to be accurate and reproducible.      

Coprecipitation as a means for the determination of zirconium traces by isotope dilution analysis in the presence of substoichiometric amounts of complexones

The possibility of using coprecipitation on Cu(OH)₂·nH₂O and Fe₂O₃·nH₂O precipitates to separate a part of zirconium unreacted with complexone in the presence of a 100-fold amount of impurities has been examined. The reaction between ethylenedia-minetetraacetic acid (EDTA) and zirconium 10⁻³−10⁻⁵ M has been used as substoichiometric reaction. A zirconium determination in the concentration range of 10⁻⁴−10⁻⁶ g/ml in artificial mixtures and steel samples has been developed using the systems of EDTA-Zr−Cu(OH)₂·nH₂O and EDTA−Zr−Fe₂O₃·nH₂O.     

Study of kinetics,equilibrium and isotope exchange in ion exchange systems. II

The kinetics of isotope exchange in the²³⁸U(VI)-²³³U(VI)-strongly acidic cation exchanger Ostion KS system was studied in the temperature range 275–307K and for total uranium concentration 2.94·10⁻⁴–1.75·10⁻² mol·l⁻¹ in UO₂(NO₃)₂ solution. The experimental results were evaluated by means of the “two-film mass-transfer model” and by the use of Fick's diffusion equations which have been proved more suitable for the system studied than McKay's equation. The influence of the temperature was evaluated using the Arrhenius equation. The diffusion character of the process follows also from the value of the activation energy (15.12 kJ·mol⁻¹). In comparison with the UO ₂ ²⁺ ↔H⁺ ion exchange⁶ the isotope exchange studied is faster and less dependent on temperature (the activation energy is substantially lower).     

Determination of Zirconium (IV) and Aluminium (III) in Waste Water

 Zirconium (IV) was determined spectrophotometrically by reaction with quercetin as primary ligand and oxalate as secondary ligand. Polyvinylpyrrolidone (PVP) was used as protective colloid to solubilize the formed zirconium quercetin oxalate ternary complex. The molar absorptivity of the 1:3:1 (zirconium–quercetin–oxalate) complex is 7.31 × 10⁴ L·mol⁻¹ cm⁻¹ at 430 nm with a stability constant of 8.2 × 10²⁰ and its detection limit is 0.16 mg/L. Beer’s law is rectilinear up to 1.46 mg/L of zirconium (IV). The sensitivity index is 1.25 ng cm⁻². The reaction of aluminium (III) with quercetin in presence of PVP as a surfactant has been studied spectrophotometrically. The molar absorptivity of the 1:3 (aluminium–quercetin) complex is 8.09 × 10⁴ × L·mol⁻¹·cm⁻¹ at 433 nm, its stability constant is 2.6 × 10¹³ with sensitivity index of 0.33 ng·cm⁻² and its detection limit is 0.08 mg/L. The optimal conditions for the quantitative determination of zirconium and aluminium were studied. The proposed methods are examined by statistical analysis of the experimental data. The methods are free from interference of most cations and anions. The proposed methods have been used to determine zirconium and aluminium in industrial waste water. Received May 30, 2001; accepted November 2, 2001; published online July 15, 2002     

Determination of dysprosium,europium, samarium and gadolinium in yttrium oxide of high purity by means of neutron activation analysis

Radioactivation analysis is the only method which allows the determination of individual rare earth element impurities in rare earth elements of high purity. The determination of dysprosium, europium, samarium and gadolinium in yttrium oxide is complicated by the short half-life of¹⁶⁵Dy (138 min.) and by the difficulty of separating traces of these elements from the matrix. A chromatographic method has been developed, for the separation of traces of Dy, Eu, Sm and Gd from ytrium, on a column packed with anion exchangerAV-17, by means of elution with 0.1N and 0.3M solutions of EDTA-sodium salt, followed by the separation of the mixture of the rare earth impurities on a microcolumn of cation exchangerKU-2, using a 0.17M solution of ammonium α-hydroxyisobutyrate as the eluent. The sensitivity of the determination of Dy, in the case of irradiating 10 mg of Y₂O₃ with a flux of 1.2·10¹³ n·cm⁻²·sec⁻¹ for 5 min. was 1·10⁻⁷%; the corresponding values for Sm, Eu and Gd, when irradiating a 100 mg sample of Y₂O₃ for 20 hours with the same flux, were 2·10⁻⁷%, 1·10⁻⁸% and 5·10⁻⁶%, respectively.     

Measurement of bromide ion used as a solute-transport monitor via epithermal neutron activation analysis

In soil science (ca. 1970), bromide ion (Br⁻) in various forms (e.g., KBr, NaBr, SrBr₂) was introduced as a non-reactive stable tracer in solute transport studies normally moving freely with the flux of water without substantial chemical or physical interactions with the soil. Typically, Br⁻ is extracted from soil and quantified using either a bromide selective electrode (sensitivity is ≈10μg/ml) or by high-performance liquid chromatography (sensitivity is ≈0.010 μg/ml). Where the sensitivity is adequate, the selective conductivity method, which is simple, affordable and fast, is preferred. More recently (ca. 1990), workers have reported that 20% of Br⁻ tracers, at low groundwater pH, may be adsorbed by iron oxides and kaolinite when present in the alluvial aquifer. We investigated the use of Epithermal Neutron Activation Analysis (ENAA) as a means of measuring Br⁻ directly in soil samples without an extraction. ENAA was chosen because of its high theoretical advantage factor over aluminum (i.e. ≈20), the principal interfering soil constituent, calculated for the⁷⁹Br(n,γ)⁸⁰Br reaction compared to²⁷Al(n, γ)²⁸Al. Br⁻ was measured (sensitivity is ≈0.050 μg/g) in one gram soil samples from a 5 s irradiation (φ_epi=2.5·10¹² n·cm^-2·s^-1) using a BN capsule.     

Cupel assay of gold by an activation method

The difficulties of determining gold in rocks and ores are due to two causes: low gold concentrations in rocks (Clark 1 to 4·10⁻⁷%), and non-uniform distribution of gold in ores. A method is proposed which is based on neutron activation of the lead alloy obtained by cupel melting in the procedure of determining gold by cupel assay. Samples of 50 to 100 g are used for cupel melting. Such large samples guarantee their representativeness. Discs of 2 to 3 g are cut from the lead alloy block and activated in a neutron flux of 10¹¹ to 10¹³ n·cm⁻² sec⁻¹. The gold content is determined from the photopeak of¹⁹⁸Au using a standard for comparison. The sensitivity of the method is 0.02 g/metric ton, its accuracy at a gold content in the order of 1.0 g/metric ton is 10% relative. The method is distinguished by the fact that it is fast and requires little labour.     

Halogen speciation in the rat thyroid: Simultaneous determination of bromine and iodine by short-term INAA

The study describes a mode of non-destructive simultaneous determination of bromine and iodine concentrations, by reactor instrumental neutron activation analysis (INAA) in the regime of short-term activation. Under the conditions of 1-minute activation in the neutron flux of 8.0·10¹³ n·cm⁻²·s⁻¹, it was possible to determine reliably as little as 5·10⁻⁸ g bromine and about 10⁻⁷ g iodine in matrices of a given type and of the mass of about 5 mg dry weight. We applied this method for the determination of Br and I concentrations in the whole rat thyroid gland as well as for the halogen speciation in fractions separated from this organ.     

Determination of phosphorus in polymers by INAA

An INAA technique employing beta spectrometry was developed for the determination of phosphorus in polymers. The (n,γ) reaction on phosphorus produces³²P, half-life 14.3 days, a pure beta emitter with end-point energy 1.71 MeV. Polymer samples in the form of powders, films and pellets are irradiated and then counted with a plastic scintillator. The beta spectrum is corrected for interferences (especially Sb, Zn and Br which are quantified by gamma spectrometry) and for energy loss in the thick sample. Samples must also be analyzed for S and Cl which cause nuclear interferences. With an irradiation time of 4 hours at a neutron flux of 5·10¹¹ n·cm^{−2 s −1}, decay time 10 days and counting time 10 minutes, the sensitivity is 520 counts/μg phosphorus and the detection limit is typically 2μg/g.