Provenance studies of obsidian artifacts: Trace elements analysis and data reduction

Iron and trace elements, such as rare-earth elements, scandium, rubidium, cesium, tantalum, thorium and uranium were determined by instrumental neutron activation analysis in geological samples of obsidian rocks from the Mediterranean Area and in obsidian artifacts found in some prehistorical human settlements in Italy. REE patterns and discriminant analysis allow a firm identification of the source material of artifacts, thus confirming and implementing fission track data of the same artifacts and rocks on the origin of the obsidian rock used to mould the artifacts.     

Determination of uranium, thorium and rare-earth elements in zircon samples using ICP-MS

Zircon is an accessory mineral, which occurs at low concentrations in a wide variety of rocks and is a host for hafnium, rare-earth elements (REE) and radio active elements like uranium and thorium. The presence of uranium in zircon has led to its increased use in the age determination of rocks. Zirconium is also considered as a strategic, hi-tech element because of its various applications, especially in the manufacturing, nuclear and aerospace industries. Analysis of zircon constitutes one of the tough tasks in analytical chemistry as it is a highly resistant mineral and it is extremely difficult to achieve its complete decomposition. In the present work, inductively coupled plasma mass spectrometry has been applied to the determination of hafnium, REE, uranium and thorium in zircon samples using two different sample dissolution procedures, one employing sodium peroxide fusion and another using a fusion mixture of KHF₂ and NaF in 3:1 ratio. Some selected zircon samples originating from different places on the eastern coast of India have been analysed by both the methods and values obtained by both methods were found to be in good agreement with each other. Though a number of international zircon reference materials are available, certified or even proposed values are available only for a very few elements in them. Two zircon reference materials have also been analysed by both methods and usable values have been proposed in this paper. The values obtained by both methods were found to compare well with each other and as well with those reported in literature. The % RSD for all the estimated elements varied from 1.0 to 12.0% at different concentration levels.     

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 4.81x10(-8), 7.23x10(-8), and 59.4x10(-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.     

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.     

Determination of rare earth elements in the biological reference materials Pine Needles and Spruce Needles by neutron activation analysis

Instrumental neutron activation analysis was applied to determine La, Ce, Nd, Sm, Eu, Tb, Yb, Lu and Sc in two biological reference materials: NIST 1575 Pine Needles and BCR-CRM 101 Spruce Needles. The purpose was to contribute to the reference data for these two reference materials. The results were obtained with a good precision (relative standard deviations less than 15%). For the Pine Needles reference material there are already some proposed values and our results showed, in general, a good agreement with the data published. The contribution of uranium fission products to La, Ce, Nd and Sm was evaluated and considered in the determination of these elements. Interferences in the determination of rare earth elements in biological materials are also discussed.     

Detection of slightly soluble systems by means of organized media in flow-injection analysis

Species that are slightly soluble in water (reagents, analytes or reaction products can be used in hydrodynamic analytical systems by means of a judicious choice of an appropriate organized medium allowing one to operate in homogeneous media with the attendant advantages. In addition, these systems allow one to improve existing analytical methods and to develop new analytical procedures. Results obtained with two types of insoluble systems are presented: those provided by 1-(2-pyridylazo)-2-naphthol (PAN) and those originating from Arsenazo III in a strongly acid medium. Detection in these systems is possible by working with an organized medium. New methods for the determination of thorium, uranium and rare-earth elements are proposed.     

Simultaneous determination of thorium and uranium in ores and SRMs by instrumental neutron activation analysis

A procedure has been developed for the determination of thoirum and uranium in ores and geological materials. The technique is relatively simple, accurate and adaptable routinely. Gamma-ray peak interferences are discussed in detail and the usefulness of the multiple gamma-ray peak ratios in the determination of the purity of peaks has been explained. The precision and accuracy of the method have been determined by analysing IAEA and NBL Standard thorium/uranium ores.     

Optical chemical sensors (Micro- and Nanosystems) for analysis of liquids

A number of peculiar analytical systems applied in production of detecting elements for chemical sensors were considered, in which organic reagents are immobilized on opaque and optically transparent polymeric matrices. Fibrous non-fabricated materials filled with powdered ion exchangers (Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences) and polymeric films coated with a high-purity gelatin layer (Mendeleev Russian University of Chemical Technology) were suggested as solidstate matrices. The conditions for determination of elements at MPC (maximal permissible concentration) levels were identified. Rapid, highly sensitive and selective techniques were developed for reflectance-spectroscopic determination of coexisting mercury(II), cadmium(II) and lead(II); chromium(VI), copper, and nickel; lanthanum, uranium(VI), and thorium, as well as for spectrophotometric determination of calcium, thorium, nitrite, and sulfate ions. Sensitive optical sensors suitable both for single control step and long-term monitoring of the content of the elements in water objects were proposed.     

Simultaneous Spectrophotometric Determination of Uranium and Thorium Using Arsenazo III by H‐Point Standard Addition Method and Partial Least Squares Regression

Simultaneous determination of uranium and thorium using arsenazo III as a chromogenic reagent at pH 1.70 by H‐point standard addition method (HPSAM) and partial least squares (PLS) calibration is described. Under optimum conditions, the simultaneous determinations of uranium and thorium by HPSAM were performed. The absorbencies at one pair of wavelengths, 649 and 669 nm, were monitored with the addition of standard solutions of uranium. The results of applying the HPSAM showed that uranium and thorium can be determined simultaneously with weight concentration ratios of uranium to thorium varying from 20:1 to 1:15 in the mixed sample. By multivariate calibration methods such as PLS, it is possible to obtain a model adjusted to the concentration values of the mixtures used in the calibration range. In this study, the calibration model is based on absorption spectra in the 600–750 nm range for 25 different mixtures of uranium and thorium. Calibration matrices contained 0.10–21.00 and 0.25–18.5 μg mL^?1 of uranium and thorium, respectively. The RMSEP for uranium and thorium were 0.7400 and 0.7276, respectively. Both proposed methods (HPSAM and PLS) were also successfully applied to the determination of uranium and thorium in several synthetic and real matrix samples.     

A simple method for the determination of uranium and thorium by delayed neutron counting

A simple method for the determination of uranium and thorium by delayed neutron counting is described. One portion of the sample is irradiated in a reactor and the delayed neutrons are counted. Another portion of the sample is mixed with B₄ C powder absorbing the thermal neutrons, and irradiated in the same position. From those data, both uranium and thorium can be calculated when a quantitative calibration has been made beforehand. The detection limits for the pure elements are 0.07 ppm for uranium and 2 ppm for thorium with the minimum analyzing time being 2 min. The accuracy of the method is investigated by comparing results obtained by the method described here with results obtained by epithermal activation 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.     

Radiographic methods for elemental analysis of boron,lithium, radium,uranium and thorium in minerals and rocks

The feasibility is discussed of applying different radiation sources for f-radiography, (n, α)-radiography and autoradiography for the determination of the spatial distribution, and the local and total concentrations of boron, lithium, radium, uranium and thorium in various materials, achieving high sensitivity and accuracy. Results demonstrating the application of the developed methods of radiography in geological practice are presented.     

Non-destructive determination of uranium and thorium in geological materials by resonance-neutron activation analysis

A simple method is described for the determination of uranium and thorium in gological materials. The samples are irradiated in a reactor with resonance and fast neutrons behind a cadmium filter. Compared with an irradiation with the whole reactor neutron spectrum, the matrix activities are reduced to about 1%, those of uranium (²³⁹Np) and thorium (²³³Pa) to about only 50 and 25%, respectively. This relative diminution of matrix activities allows the γ-measurement of²³⁹Np and²³³Pa as early as after two days' cooling time; in samples with high uranium contents the determination of²³³Pa requires one month's cooling time. This non-destructive procedure yields a detection limit of 0.1 ppm for uranium and thorium in samples of 200 mg, with an error of ±5%. Dedicated to ProfessorW. Borchert on the occasion of his 60th birthday.     

Determination of rare earth elements in international geochemical reference materials

Instrumental neutron activation analysis of eight geochemical standard materials has been carried-out and the concentration values of nine rare-earth elements (REE) (La, Ce, Nd, Sm, Eu, Gd, Tb, Yb and Lu) have been determined. Discussion of some problems in the determination of those elements is presented and the results obtained are compared with literature values. In general, good agreement with available data was obtained but discrepancies with concentration values for a number of elements in some of these standards are discussed.     

Untersuchungen an Geologischen Materialien Durch Messung der Natürlichen Gamma-aktivität

Investigations of natural activity of several geological materials by γ-spectrometry using a Ge(Li)-detector are described. The determination of thorium and uranium contents is possible up to minimum concentrations of about 10 ppm Th and 1 ppm U. The results of this method are compared with results of different methods of activation analysis. In the most cases the agreement is very well. If the decay-chain of²³⁸U is not in equilibration, it is possible to estimate the geological oldness of the sample in a range between about 20 000 and 200 000 years.     

Quantitative Auswertung von Dünnschicht-Chromatogrammen: On line-Kopplung mit programmierbaren elektronischen Tischrechnern

Reprocessing of spherical THTR fuel elements shall be tested in the Jülich pilot plant JUPITER. This fuel type differs significantly from other fuel elements with respect to shape, composition and fissile material content. It requests special provisions for reprocessing and the necessary material balancing and safeguarding. Two material balance areas (MBA) are defined: head end and chemical extraction process. Within the 1. MBA uranium and thorium are balanced mainly by using a combination of digital counting of the fuel spheres, gammaspectrometric burn-up determination of individual spheres and X-ray fluorescence determination of uranium and thorium in nitric acid solutions which have been obtained by dissolution in Thorex reagent of the heavy metal oxides after burning of the graphite matrix. The 2. MBA begins with the solution for the chemical extraction process, collected in the so called accountability tank. After extraction according to the Thorex flowsheet the process streams are monitored in line for process control, and off line for material balancing and safeguarding. This is performed mainly by X-ray fluorescence analysis, potentiometric titrations, alpha- and mass spectrometry.     

Determination of rare earth elements in hot spring and crater lake waters by epithermal neutron activation analysis

Determination of the rare earth elements (REE's) in acidic hot spring and crater lake waters by neutron activation analysis (NAA), in which activation was performed mostly by epithermal neutrons (epithermal NAA) was investigated. Nine REE's, La, Ce, Sm, Eu, Tb, Ho, Tm, Yb and Lu, out of fourteen naturally existing REE's were determined at ppb levels with satisfactory precision. The epithermal NAA was found to be more effective in the determination of Sm, Tb, Ho and Yb than normal NAA, in which activation was performed mainly by thermal neutrons. Combined use of the epithermal and normal NAA's enabled the determination of eleven REE's, La, Ce, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb and Lu.     

Determination of rare-earth eleemnts in rock samples by neutron activation analysis

A Ge(Li) detector combined with cation exchange separation has been used for the determination of 12 rare-earth elements (La, Ce, Nd, Sm, Eu, Gd, Tb, Ho, Er, Tm, Yb, and Lu) in rock samples by neutron activation analysis. After purification by the conventional hydroxide-fluoride precipitation, the rare-earth elements are separated into two fractions, light (La-Tb) and heavy (Ho-Lu), by EDTA cation exchange, and the γ-activities of the two fractions are measured by a Ge(Li) detector. The heavy rare-earths, such as Ho, Er, and Tm, can be easily γ-counted without serious interference from the intense Compton background and photopeaks due to the light rare-earths such as¹⁴⁰La,¹⁵³Sm,¹⁵²Eu, and¹⁶⁰Tb. The chemical yields (60%) for the individual rare-earths are determined by a reactivation technique. The results obtained for the U.S. Geological Survey standard rocks G-1 and W-1 are compared with the previously reported data.     

Surface cleaning techniques: ultra-trace ICP-MS sample preparation and assay of HDPE

The world’s most sensitive radiation detection and assay systems depend upon ultra-low-background (ULB) materials to reduce unwanted radiological backgrounds. In this study, we evaluate methods to clean HDPE, a material of interest to ULB systems and the means to provide rapid assay of surface and bulk contamination. ULB-level material and ultra-trace-level detection of actinide elements is difficult to attain, due to the introduction of contamination from sample preparation equipment such as pipette tips, sample vials, forceps, etc and airborne particulate. To date, literature available on the cleaning of such polymeric materials and equipment for ULB applications and ultra-trace analyses is limited. For these reasons, a study has been performed to identify an effective way to remove surface contamination from polymers in an effort to provide improved instrumental detection limits. Inductively Coupled Plasma Mass Spectroscopy was utilized to assess the effectiveness of a variety of leachate solutions for removal of inorganic uranium and thorium surface contamination from polymers, specifically high density polyethylene (HDPE). Leaching procedures for HDPE were tested to optimize contaminant removal of thorium and uranium. Calibration curves for thorium and uranium ranged from 15 ppq (fg/mL) to 1 ppt (pg/mL). Detection limits were calculated at 6 ppq for uranium and 7 ppq for thorium. Results showed the most effective leaching reagent to be clean 6 M nitric acid for 72 h exposures. Contamination levels for uranium and thorium found in the leachate solutions were significant for ultra-low-level radiation detection applications.     

Mössbauer Study of El-Bahrain Meteorite

Procedures for the determination of traces of rare earth elements (REE) in geological samples by instrumental neutron activation analysis (INAA) and high resolution liquid chromatography (HPLC) are presented. The international standard reference materials AGV-1, GSP-1 and G-2 (USGS) were tested for the determination of REE concentrations using both techniques. The results obtained showed good agreement with certified values, giving relative errors less than 10%. By using INAA, the REE La, Ce, Nd, Sm, Eu, Tb, Yb and Lu were determined. All the REE, except Dy and Y, were determined when HPLC was employed. The application of INAA and HPLC to the determination of REE in geological samples is also discussed.