Determination of the REE in environmental samples near a coal power station based on k0-standardized NAA with counting in a LEPD

The Ree contents in lichens and plants determined by k₀-standardized NAA with LEPD and HPGe are compared. We obtain similar values for Sm, Eu, Tb and Yb and better values for Ce and Nd by using LEPD Besides, LEPD allows the determination of Gd, Tm and Lu. The study of REE concentrations in the neighbourhood of two coal power stations show that: i) in the station under construction (C. T. Pego), the index of accumulation of each REE by the lichens and olive tree leaves is identical in two sampling loci where the soils have different REE concentration; and ii) in the station in operation (C. T. Sines), the REE contents in the soils is identical and the differences observed in the lichens and wild terrestrial plants are most probably due to the fly-ashes emmission from the station.     

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.     

Determination of rare earth elements in recent and fossil shells by radiochemical neutron activation analysis

Seven rare earth elements (La, Ce, Sm, Eu, Tb, Yb and Lu) in marine shell samples were determined by neutron activation analysis. In order to measure γ-ray using a Ge(Li) detector without serious interference from the intense Compton background from²⁴Na, a simple radiochemical separation was performed by a co-precipitation method with hydrated iron(III) oxide. The chemical yields for shell samples (91–99%) were determined by a re-activation technique for Gd and Yb. The interference from the²³⁵U(n, fission) reaction was corrected for determination of La and Ce. The data obtained in this study showed the behavior of rare earth elements in shells during the process of fossilization.     

Determination of trace elements in carbonates by instrumental neutron activation analysis

A systematic non-destructive determination of eighteen trace elements (F, Na, Cl, Sc, Mn, Zn, Br, Sr, I, Ba, La, Ce, Sm, Eu, Tb, Yb, Th and U) in carbonate samples by thermal neutron activation analysis was developed. Three 0.2–0.5g samples were irradiated for 15 sec (in the case of determination of F), for 3 min (in the case of Na, Cl, Mn, Sr and I) and for 60 hrs (in the case of Sc, Zn, Br, Ba, La, Ce, Sm, Eu, Tb, Yb, Th and U) in the TRIGA MARK II Reactor at a thermal neutron flux of 5·10¹¹ n·cm⁻²·sec⁻¹ (15 sec and 3 min irradiation) and 1.5·10¹²n·cm⁻²·sec⁻¹ (60 hrs irradiation), respectively. According to the half life of the nuclides formed, the activities were measured with a Ge(Li) spectrometer as follows,²⁰F∶15 sec counting after 20–25 sec cooling,²⁴Na,³⁸Cl,⁵⁶Mn,^87mSr and¹²⁸I∶600 sec couting after 30–120 min cooling,⁸²Br,¹⁴⁰La,¹⁵³Sm,¹⁷⁵Yb and²³⁹Np (daughter of²³⁹U)∶3000 sec counting after 1 week cooling,⁴⁶Sc,⁶⁵Zn,¹³¹Ba,¹⁴¹Ce,¹⁵²Eu,¹⁶⁰Tb and²³³Pa (daughter of²³³Th)∶5000 sec counting after 1 month cooling. The errors due to the fluctuation of the neutron flux and the counting geometry were minimized by the use of calcium determined previously with EDTA-titration as an internal standard. The interferences from²⁴Mg(n, p)²⁴Na and²³⁵U(n, fission) reactions were corrected by the activities produced by the reactions in unit weight of magnesium and uranium, and their concentrations in samples measured experimentally. The data of Na, Mn, Zn and Sr were compared with the results obtained by atomic absorption analysis.     

Radiochemical neutron activation analysis determination of rare earth elements in geological materials with ppb sensitivity

Rare earth elements are determined, with ppb sensitivity, by radiochemical activation analysis using a fusion dissolution process and a quantitative group separation scheme, followed by radioassaying. Spectral interference is avoided, or corrected for, by repeating the counting operation with a delay of four to six weeks. This allows for the decay of shorter lived interfering isotopes such as¹⁵⁵Eu on¹⁶⁰Tb and¹⁷⁵Yb on¹⁴¹Ce. The scheme is rapid, sensitive and uses standard radiochemical laboratory facilities and counters. It has been applied to a wide range of rocks and minerals and data for eleven rare earths (La, Ce, Nd, Sm, Eu, Gd, Tb, Ho, Tm, Yb and Lu) is presented here and compared with literature values.     

ICP-AES and D.C.arc-AES determination of Sc, Y and lanthanides in nuclear grade graphite

Summary Inductively Coupled Plasma-Atomic Emission Spectrometric and Direct Current Arc-Emission Spectrometric methods have been developed for the determination of rare earths in nuclear grade graphite. The graphite matrix was selectively removed from the analytes by controlled heating in air at 900°C in a muffle furnace. The residual ash containing analytes was dissolved and analysed by ICP-AES for rare earths specially required for assessing the nuclear purity, viz. Dy, Eu, Gd and Sm and for all rare earths, Sc and Y by D.C.arc-AES by photographing their spectra in III order on an 3.4 M Ebert Spectrograph. The recovery of rare earths after ashing was confirmed using -activities of¹⁴¹Ce,^152–154Eu,¹⁵³Gd,¹⁷⁰Tm and¹⁶⁹Yb which was found to be quantitative within experimental error.

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Bestimmung von Sc, Y und Lanthaniden in nuklear-reinem Graphit mit Hilfe der ICP-AES und der Gleichstrombogen-Spektrometrie

     

Determination of rare earths in silicate rocks by epithermal neutron activation and a simple group separation

The determination of nine rare earth elements in rock samples by epithermal neutron activation, followed by a simple group-separation procedure and Ge(Li) γ-ray spectrometry, is described. This method is found to be advantageous for the determination of Nd, Gd, Ho, Er and Lu by means of the short-lived nuclides¹⁴⁹Nd,¹⁵⁹Gd,¹⁶⁶Ho,¹⁷¹Er and^176m Lu. Precision for La, Sm and Eu is similar to that of thermal neutron activation, that for Dy is worse. Samples of the standard rocks, basalt BCR-1 and granite G-2, were analyzed by this procedure and the results obtained are compared with previously reported data.     

Determination of rare earths in rare-earth concentrates by neutron activation analysis

Neutron activation analysis was applied to the determination of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Yb, Lu and Th in rare-earth concentrates resulting from minerals. High-resolution gamma-ray spectrometry with a Ge(Li) detector was used for the non-destructive determination, and a single comparator method using Co as flux monitor was applied.     

Determination of 32 elements in rocks by neutron activation analysis and high resolution gamma-ray spectroscopy

Neutron activation analysis and Ge(Li) spectroscopy was used to determine 32 elements in seven U.S.G.S. standard rocks of a wide range of composition. Short half-life nuclides (10 sec-10 min) were used to measure Sc, Hf, Dy, Mg, Al, Ca, Ti, V (and Na) in an automated rabbit Ge(Li) detector system. The elements K, Cu, Zn, Ga, Sr, Ba, La, Eu, Sm (and Mn) were determined by dissolution of the irradiated sample followed by removal of²⁴Na on hydrated antimony pentoxide (HAP). Long-lived nuclides were used to measure Sc, Cr, Fe, Co, Zr, Rb, Sb, Cs, Ba, Ce, Eu, Yb, Tb, Lu, Hf, Ta and Th after decay of²⁴Na. The method involves little radiochemistry and the separation is selective for²⁴Na under the experimental conditions used. Elemental concentrations determined agree well with previously published data.     

The use of photon activation analysis for the determination of Sm,Eu, Gd and Dy in boron carbide

An installation for photon activation analysis recently completed at CBNM, Geel, is described. Synthetic standards prepared from pure graphite are used for the non-destructive determination of lanthanides in boron carbide. The induced activities of¹⁵³Sm,^152mEu,¹⁵⁹Gd and¹⁵⁷Dy were measured using a single open-ended coaxial Ge(Li) detector and the photopeak areas were calculated using the GAFIT program. For the irradiation parameters used, the limits of detection are communicated. This paper has been presented at the 5th Symposium on the Recent Developments in Activation Analysis. 17th–21st July, 1978, St. Catherine's College, Oxford.     

Determination of rare-earth elements in rock samples by neutron activation analysis with a lithium-drifted germanium detector after chemical group-separation

A lithium-drifted germanium detector combined with chemical group-separation has been utilized for the determination of rare-earth elements (La, Ce, Nd, Sm, Eu, Gd, Tb, Tm, Yb and Lu) in rock samples by neutron activation. This procedure has the advantage of a low background level which cannot be attained in the non-destructive method. The combination of the Ge(Li) detector and chemical group-separation also offers a distinct simplification in the correction of contributions from other nuclides. For optimum utility of a Ge(Li) detector in neutron activation analysis, chemical group-separations are recommended.     

Determination of the contents and distribution characteristics of REE in natural plants by NAA

The concentration of 8 REEs (La, Ce, Nd, Sm, Eu, Tb, Yb and Lu) in 17 species of plants and their host soil, which were collected from a rare earth ore area located in the south of China, have been determined by INAA. The chondritic normalized REE patterns for different parts of plants (e.g., leaf stem and root) and their host soils were studied. The results showed that the concentration levels of REE for most plants in the sampling area were elevated. Particularly, the leaves of the fern (Dicranopteris dichotoma) contain extremely high concentration of the total REE (675–3358 g/g) Generally, these REE distribution patterns in every part of plants were very similar and reflected the characteristics of their host soils. However, the chondritic normalized REE patterns in some plants relative to the host soil revealed obvious fractionation, such as the depletion of the heavy REE (for fernCitrus reticulata andBrassia campestris), the heavy REE enrichment (forCamellia sinensis, Camellia oleifera andZiziphus) and the Ce positive anomaly (forGardenia jasminoides).     

Determination of trace amounts of gold in the presence of rare earth elements in rock samples from Makhtesh Ramon (Southern Israel), by instrumental epithermal neutron activation analysis

Epithermal neutron activation analysis (ENAA), followed by high resolution gamma-ray spectrometry, was applied to determine trace amounts of Au in the presence of rare earth elements (REE) from vein samples in the basaltic rocks of Makhtesh Ramon, located in southern Israel. The contribution of¹⁵²Eu (411.1 KeV) to the 411.8 keV peak of¹⁹⁸Au was determined using multiple gamma-peak, ratios derived from Eu standards and mixtures of Au and Eu. The concentration of Au was found to be in the range of 10–80 ppb. A group of rare earth elements: La, Eu, Ce, Tb, Sm, Lu, Yb was identified; the concentration of Eu was found to be 0.5 ppm.     

Grundlagen zur halbquantitativen Bestimmung der Elemente in der Laser-Mikrospektralanalyse. II

Zusammenfassung Für die folgenden Elemente wurden die Grundlagen für eine halbquantitative Konzentrationsbestimmung mit Hilfe des Laser-Mikrospektralanalysators ermittelt, und zwar differenziert für Untersuchungen an oxidischen und an metallischen(^*) Materialien: Li, B, Na, P, K, Ca, Sc, Ti, V^*, Ge, As^*, Sr, Y, Zr^*, Nb, Pd, Te, Ba, La, Ce, Nd, Eu, Gd, Er, Yb, Lu, Hf, Ta, W^*, Ir, Pt^*, Au, Hg^*.

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Principles of semi-quantitative determination of elements by laser-microspectroscopy. II

The principles for the semi-quantitative determination of the following elements by laser-microspectroscopy have been investigated separately for oxidic and metallic(^*) materials: Li, B, Na, P, K, Ca, Sc, Ti, V^*, Ge, As^*, Sr, Y, Zr^*, Nb, Pd, Te, Ba, La, Ce, Nd, Eu, Gd, Er, Yb, Lu, Hf, Ta, W^*, Ir, Pt^*, Au, Hg^*.

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Teil I: H. Schorth [3].     

A Revised Periodic Table: With the Lanthanides Repositioned

The lanthanide elements from lanthanum to lutetium inclusive are incorporated into the body of the periodic table. They are subdivided into three sub-groups according to their important oxidation states: La to Sm, Eu to Tm, Yb and Lu, so that Eu and Yb fall directly below Ba; La, Gd, Lu form a column directly below Y; Ce and Tb fall in a vertical line between Zr and Hf. Pm falls below Tc; both are radioactive, and not naturally occurring. The elements with easily attained 2⁺ and 4⁺ oxidation states are grouped and clearly differentiated. Gadolinium has an important position as the centre of four triads in the block of elements that surround it– La, Gd, Lu; Ba, Gd, Hf; Eu, Gd, Tb; Yb, Gd, Ce. This new arrangement has the advantages of compactness, simplicity and clarity – there are no tie lines; and important oxidation states of these metals are emphasized. The actinides are also accommodated within this system, and element 114 falls naturally below lead in Group 14.     

Relative efficiency calibration of Ge(Li) detector in low energy region

The relative gamma-ray intensities in the energy region between 122 and 411 keV in the decay of¹⁵²Eu were measured by using a Ge(Li) detector. Its efficiency calibration was carried out with the radioactive sources of²⁴¹Am,⁵⁷Co,²⁰³Hg,¹³⁷Cs,¹³³Ba,⁷⁵Se,¹⁶⁹Yb and¹⁹²Ir.     

Rare earth element patterns in Nigerian coals

Rare Earth Elements (REE's) retain group coherence in their environment and are therefore useful geochemical markers. We report the pattern of ten REE's (La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Yb, Lu) determined by Instrumental Neutron Activation Analysis (INAA) for coals obtained from eight mines in Nigeria, namely, Okaba, Enugu, Ogbete, Onyeama, Gombe, Lafia, Asaba and Afikpo. Our results show the existence of fractionations with the highest index of 13.19 for Lafia coal, depletion in HREE, negative Eu anomaly for most of the coals, REE patterns that are consistent with chondritic trends; prominent (Eu/Eu^*)_cn for Okaba and Gombe coals. Variations in geochemical data observed could suggest strong departures from band metamorphism during the coalification events of the Benue Trough geosynclines, where the coal deposits are all located.     

Rare earth elements determination and distribution patterns in sediments of a polluted marine environment by instrumental neutron activation analysis

Results obtained from the analysis of sediment core samples taken froma fairly polluted marine environment were analyzed for the REE contents todetermine the concentrations of La, Ce, Sm, Eu, Tb, Dy and Yb using instrumentalneutron activation analysis. Core samples were divided into strata of between2 to 3 cm intervals and prepared in the powdered form before irradiating themin a neutron flux of about 5.0 . 10¹² n . cm ^—2s ^—1 in a Triga Mark II reactor. Down-core concentration profilesof La, Ce, Sm, Eu, Tb, Dy and Yb in 3 core sediments from three sites areobtained. The shale-normalized REE pattern from each site was examined andlater used to explain the history of sedimentation by natural processes suchas shoreline erosion and weathering products deposited on the seabed and furnishingsome baseline data and/or pollution trend occurring within the study area.The shale-normalized REE patterns also showed that LREE in the sediment samplesexhibit enrichment relative to HREE particularly, La and Sm showing enrichmentcompared to the ratios in shale. REE concentrations of 124 µg/g at thesurface of sediment collected at two of the three sites were found to decreaseto 58 and 95 µg/g, respectively. This was of particular interest whenit is used to explain the anomalies occurring in the marine sediment as aresult of geochemical processes over a long period of time. Changes in concentrationsfrom surface to bottom of the sediments ratioed to Sm concentrations and thecorrelation between concentrations of Sm and these elements were also investigatedand correlation coefficients were calculated for all REEs and sites. Validationof the method used was done using a Soil-7 SRM.     

Determination of rare earth and other elements in standard biological samples by ICP-MS and activation analysis

Various rare earth elements (REEs) in standard samples supplied by the IAEA namely mussel (IAEA-142) and lichen (IAEA-336) were examined by ICP-MS and INAA. For ICP-MS, 200 mg each of the samples were dissolved in conc. nitric acid using a microwave sample-preparation system. After repeated concentration-dilution procedures (final volume; 10–20 ml), 1 ml of the sample was supplied for assay. La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb could be detected in the order of magnitude of 10⁻³ ng/g. Activation analysis carried out using 300 mg of the sample powders failed to detect REEs except La, Ce, Sm and Eu because of a strong interference due mainly to²⁴Na and³²P induced in the samples by irradiation. The REE patterns (NASC-normalized) obtained for both the organisms are of the same in their shapes except for all the values for sea animal mussel which are somewhat higher than those for land plant lichen. However, we found a large difference in the other elements contents between the two organisms. For example, Na, Cl, Mg, K, and Ca contents in mussel are about 26, 7, 4.5, 3.5, and 2 times, those in lichen. As the concentrations in the sea water for these elements is from 10² (K and Ca) to 10³ (Na, Cl and Mg) order of magnitude higher than in the land water, the result seems reasonable to assume that the higher the concentration of the element around the organisms the higher its content in the organisms.     

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.