Determination of Rare-Earth Elements in Sulfide Minerals by Inductively Coupled Plasma Mass Spectrometry with Ion-Exchange Preconcentration

A procedure was developed for determining ultratrace rare-earth elements in sulfide minerals by inductively coupled plasma mass spectrometry with ion-exchange preconcentration. The concentration factor was 200. The found concentrations of rare-earth elements were 6–30 times lower than those in chondrites. For lanthanum and praseodymium, RSD < 10%; for other rare-earth elements, RSD < 6%. The accuracy of the results was verified by the addition of known amounts of Eu, Tb, Tm, and Lu to a chalcopyrite sample at the stage of decomposition with HCl and HNO₃. The calculated yield of rare-earth elements was 94–96%. The detection limit was from 0.06 ng/g (6 × 10^–9%) for lutetium to 5 ng/g (5 × 10^–7%) for cerium. The procedure was used for the determination of rare-earth elements in chalcopyrites, pyrites, and sphalerites.     

Auxiliary functions for Slater molecular integrals

Summary Some types of recurrence relations are modified to overcome the cases in which their conventional application is unstable in both the forward and backward directions. The original recurrence relations — connecting adjacent elements — are replaced by more general ones, where the non-adjacent elements are connected by coefficients obtained by new sets of relations derived from the original ones. This modification can be helpful for the calculation of the complicated molecular integrals with Slater Type Orbitals (STOs).As a simple test we prove that some auxiliary functions — previously evaluated by expensive expansions — appearing in two-center two-electron integrals can be thus calculated with very low computer cost and high accuracy.     

Erste Ergebnisse einer Ringanalyse zur Erstellung eines internen Buchenblatt-Referenzmaterials für ?kosystemuntersuchungen

Summary To evaluate pollution effects on ecosystems, more and more plant and animal samples are analyzed for their concentrations of pollutants and nutrient elements. Since chemical analyses of biological materials are largely influenced by matrix effects, their accuracy depends on the availability of reference materials. Unfortunately only very few such standards exist so far. The described interlaboratory comparison of beech leaves from Baden-Württemberg demonstrates the possibility of producing reference materials from selected organisms, which — though not certified — are sufficient for research projects. Apart from their function as reference materials, those standards show typical levels of elemental concentrations for their region of origin. First results are introduced.     

Rational Combination of the Dissolution of Some Inorganic Compounds of Rare-Earth Elements with the Determination of Chemical Forms of Major Constituents in These Compounds

It was found that the major constituents (F^– and S^2–) in fluorides, sulfides, and sulfofluorides of rare-earth elements, and europium(II) in europium fluoride, can be determined titrimetrically. Peculiarities of the decomposition and analysis of initial samples of these compounds and samples after high-temperature treatment in vacuum were considered. The analytical procedures are based on the combination of the decomposition of the test materials using solutions of iodine (determination of S^2–), boric acid (determination of F^–), and vanadium(V) salts (determination of europium(II) salts) and the final titration of excess reagents that selectively reacted with a chemical form of the analyte. Potentiometry with an ion-selective electrode was also used in the determination of fluoride ions. The total concentration of rare-earth elements was determined by chelatometry.     

Production of volatile trisacetylacetonates of rare-earth elements by heating their hydrates

Conclusions The heating of the hydrates of the trisacetylacetonates of heavy rare-earth elements under vacuum in an atmosphere saturated with dry acetylacetone vapor leads to the sublimation of the anhydrous acetylacetonates and, in a number of cases, their hydrated or hydrolyzed forms. The light rare-earth elements do not form compounds which sublime under these conditions. In the series of rare-earth elements of the yttrium subgroup the yield of the sublimate, which is insignificant for dysprosium, increases to 100% in lutetium and ytterbium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1207–1211, June, 1984.     

Structure of ethylenediaminetetraacetates of rare-earth elements in crystals and solutions

The variation in the structure of the ethylenediaminetetraacetates of the series of rare-earth elements in crystals and in solutions was studied by various experimental methods. It was established that crystalline complexes with identical structure exist throughout the whole series of rare-earth elements, with a coordination number of 9 (and, possibly, 8 in the yttrium group) and with three coordinated water molecules. They were studied by the x-ray erystallographic method. Such structures are not formed in solutions. In the crystals they are thermo-dynamically stable for the cerium group and decompose spontaneously in the yttrium group, changing into the more stable form KLnEDTA·2H₂O, similar in structure to the dissolved complexes of this group. It was established that the anhydrous complexes do not exist. The EDTA is hexadentate throughout in the crystals, and pentadentate in solutions from La to Nd. From Nd to Tb there is an equilibrium between two forms with pentadentate and hexadentate EDTA and a coordination number of 8, and this is followed by a decrease to a coordination number of 7 and an increase to hexadentate at the end of the series. In complexes of the cerium group in solution three molecules of water are coordinated, and in the center of the series there is an equilibrium between forms with three and two water molecules, which decreases to one water molecule at the end of series. The number of isomers of the complexes of EDTA with the rare-earth element (from neodymium, to lutecium) is 2. The thermodynami'c characteristics of the LnEDTA^– complexes are fully explained by the variation of their structure in the series of rare-earth elements.Translated from Teoreticheskaya i Éksperitmental'naya Khimiya, Vol. 21, No. 4, pp. 440–450, July–August, 1985.     

Separation of cerium-group rare-earth elements on PAN-FOSPAN fibrous sorbent

The selectivity of sorption of cerium-group rare-earth elements on acid- and base-treated fibrous complexing PAN-FOSPAN ampholyte from aqueous solutions containing acetate and butyrate anions was studied as influenced by pH. The possibility of separating Nd³⁺ from Eu³⁺ by eluent chromatography on PAN-FOSPAN was studied. The conditions for concentrating the sum of rare-earth elements on the resin were found.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 11, 2004, pp. 1775–1778.Original Russian Text Copyright © 2004 by Skvortsova, Selivanova.     

Simultaneous Spectrophotometric Determination of Rare-Earth and Transition Elements Using Partial Least-Squares (PLS) Multivariate Calibration

A spectrophotometric method for the simultaneous determination of rare-earth and transition elements in synthetic superconductors, [(La_{1 – x} Eu _x )_1.82Sr_0.18CuO₄], by the use of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) as chelating agent was developed. The influence of chemical variables affecting the reaction was studied. A partial least-squares (PLS) multivariate calibration procedure was used to assess the data obtained from several calibration solutions measured over the wavelengths range 400–700 nm. The concentration range for Cu was (1–12) × 10^–6 mol/L, while the range for the rare-earth elements La and Eu was (2–8) × 10^–6 mol/L. The relative errors in the determinations were less than 5% in most cases.     

Peculiarities in the Behavior of Rare-Earth Elements in Their Determination in Black Shales by Inductively Coupled Plasma Mass Spectrometry

The accuracy of the results of analysis by inductively coupled plasma mass spectrometry (ICP-MS) was studied for the determination of rare-earth elements in black shales rich with a carbonaceous organic substance of a different nature: biogenic (samples SChS-1 and SLg-1, which were put through certification studies at the Institute of Geochemistry, Siberian Division, Russian Academy of Sciences) and bituminous (SDO-1 and SGR-1, reference samples of the US Geological Survey). Based on the comparison of the results obtained by ICP MS with the reference data for SChS-1 and SLg-1 shales, it was found that the systematic error depends on the procedure of sample decomposition: in open systems (A), in autoclaves (B), and by fusion with lithium metaborate (C). In decomposition procedures A and B, the underestimation of results was observed for heavy rare-earth elements (Gd–Lu): up to 60–80% in the open decomposition of samples and up to 30–40% in the decomposition in an autoclave; these errors cannot be eliminated by preliminary calcination of samples, and only the use of procedure C provides the smallest deviations between the found and reference concentrations. The behavior of rare-earth elements in the analysis of SDO-1 and SGR-1 shales differs from their behavior in the analysis of SChS-1 and CLg-1: systematic errors were not revealed when the above decomposition procedures were used.     

Nd(III) and Gd(III) Sorption on Mesoporous Amine-Functionalized Polymer/SiO2 Composite

The strong demand for rare-earth elements (REEs) is driven by their wide use in high-tech devices. New processes have to be developed for valorizing low-grade ores or alternative metal sources (such as wastes and spent materials). The present work contributed to the development of new sorbents for the recovery of rare earth ions from aqueous solutions. Functionalized mesoporous silica composite was synthesized by grafting diethylenetriamine onto composite support. The physical and chemical properties of the new sorbent are characterized using BET, TGA, elemental analysis, titration, FTIR, and XPS spectroscopies to identify the reactive groups (amine groups: 3.25 mmol N g⁻¹ and 3.41 by EA and titration, respectively) and their mode of interaction with Nd(III) and Gd(III). The sorption capacity at the optimum pH (i.e., 4) reaches 0.9 mmol Nd g⁻¹ and 1 mmol Gd g⁻¹. Uptake kinetics are modeled by the pseudo-first-order rate equation (equilibrium time: 30–40 min). At pH close to 4–5, the sorbent shows high selectivity for rare-earth elements against alkali-earth elements. This selectivity is confirmed by the efficient recovery of REEs from acidic leachates of gibbsite ore. After elution (using 0.5 M HCl solutions), selective precipitation (using oxalate solutions), and calcination, pure rare earth oxides were obtained. The sorbent shows promising perspective due to its high and fast sorption properties for REEs, good recycling, and high selectivity.     

Application of light guides on the PLASMAQUANT-110 ICP spectrometer — Analytical capabilities and analytical performance

Summary On a high-aperture, high-resolution Echelle spectrometer individual fibre light guides are used to transmit the spectral light from the focal plane to the detectors. For this purpose, 132 light guides are arranged behind an exit slit mask. These light guides transmit the light of the spectral lines of 70 elements. The application of light guides provides numerous advantages for analytical program changes and extensions and enables fast survey analyses. Thoroughly chosen fibre types and precise arrangement of light guides are the prerequisites for a good analytical performance which — beside reproducibilities of lines and background as well as detection limits — is exemplified by the spectral resolution of boron and iron lines as well as of the iron triplet at 310 nm.     

Use of organic reagents for the voltammetric determination of rare-earth elements

The data on organic reagents used for the voltammetric determination of rare-earth elements (REE) is surveyed. The mechanisms of the reduction of complexes formed by REE with some reagents are presented. Procedures for determining REE in real samples using organic reagents are briefly characterized.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 4, 2005, pp. 342–348.Original Russian Text Copyright © 2005 by Dubenskaya, Levitskaya, Poperechnaya.     

Multielement determination in water by instrumental neutron activation analysis

Instrumental neutron activation analysis /INAA/ technique has been applied to a water sample to determine the elemental concentrations. The sample was irradiated with a neutron flux of 1.2×10¹² n cm^–2 s^–1 for two different periods followed by counting at three different decay times, using two coaxial type high-resolution Ge/Li/ detectors. The dominant elements determined in the water sample are Ca, Cl, Na, Mg, and K present in ppm-level while Co, I, Mn, Sm, and Sb are present in smaller amounts, approximately on the average 0.01 ppm. Only traces of other elements such as the rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water sample.     

Analysis of the CCRMP Oka-2 rare-earth reference mineral of the britholite-apatite series by electrothermal atomic-absorption and inductively-coupled plasma atomic-emission spectrometry

The lanthanides and yttrium in the Canadian Certified Reference Materials Project (CCRMP) new rare-earth mineral reference material, Oka-2, were determined by electrothermal atomic-absorption and inductively-coupled plasma atomic-emission spectrometry (ICPAES) after sample decomposition with acids and separation of the rare-earth metals from phosphate and other matrix elements by precipitation as fluorides and oxalates. Thorium, yttrium and the common major and minor elements were determined by ICPAES after sample decomposition by fusion with lithium meta- and tetraborates and dissolution of the melt in a mixture of dilute nitric acid and ethylenediaminetetra-acetic acid solution. For comparison purposes, silicon, phosphorus, calcium, magnesium and iron were also determined by other methods. The results obtained are compared with other CCRMP values and with those obtained previously for a similar rare-earth mineral from the same geographical area. Oka-2 is considered to be a thorian intermediate member of the britholite—apatite series.     

Concentration levels of rare-earth elements and thorium in plants from the Morro do Ferro environment as an indicator for the biological availability of transuranium elements

Plants and soils from a natural thorium and rare-earth element occurrence (Morro do Ferro, Brazil) were analyzed by alpha spectrometry (Th) and ICP-AES (REE), after pre-concentration of the elements by solvent extraction, co-precipitation and ion exchange procedures. Leaching experiments with humic acid solutions and different soils were performed to estimate the fraction of elements biologically available. High concentrations of the light rare-earth elements (LREE) and of Th, reaching some hundreds of g/g-ash, were measured in plant leaves from the areas of the highest concentration of these elements in soil and in near-surface waters. Chondrite normalized REE plots of plant leaves and corresponding soils are very similar, suggesting that there is no significant fractionation between the REE during uptake from the soil solution and incorporation into the leaves. However, Ce-depletion was observed for some plant species, increasing forSolanum ciliatum in the sequence: leaves<fruits<seeds. Soil to plant concentration ratios (CR's) for Th and the REE, based on the total concentration of these elements in soils, are in the range of 10^–3 to 10^–2. Leaching experiments confirmed the importance of humic acid complexation for the bio-uptake of Th and REE and further showed that only a very small fraction of these elements in soil is leachable. The implications of these results on the calculated CR's will be discussed.     

Proof of the generalized expressions for the number of perfect matchings of polycube graphs

The number of perfect rnatchings for the linear 2 × 2 ×n cubic lattice was analytically derived by diagonalizing the skew—symmetric 4n × 4n determinant, whose non—zero off—diagonal elements are either ±1 or ±i (pure imaginary number). The basic formulation invoking the matrix manipulation follows that of Kasteleyn, but the result obtained in this paper is the first example of the analytical solution for a special case of the three-dimensional Ising model.received by the Publisher 20 September 1989     

Ion-exchange chromatography with an oxalic acid-α-hydroxyisobutyric acid eluent for the separation and quantitation of rare-earth elements in monazite and xenotime

Summary An oxalic acid-α-hydroxyisobutyric acid eluent has been used for the separation and determination of rare-earth elements by high-performance ion-exchange chromatography. Fifteen rare-earth elements were separated within less than 25 min on a 150×4.6 mm i.d. column packed with 5-μm sulfonic acid-bonded silica particles by elution with a combined gradient of 0.60–9.0 mM oxalic acid and 19.0–5.0 mM α-hydroxyisobutyric acid at pH 4.6. Detection and quantitation of the separated rare-earth elements was accomplished by visible-absorbance measurements at 600 nm after postcolumn reaction with arsenazo I. The gradient of the two complexing agents was optimized to enable the separation of yttrium(III) without interference from other elements, especially dysprosium(III) and terbium(III). Mass detection limits of the elements were in the range of 2–4 ng. Finally, the chromatographic system was applied to the quantitative analysis of rare-earth elements in monazite and xenotime.     

Determination of the stability constants of mono- and ditartrates of the rare-earth elements

Conclusions The stability constants and confidence intervals for monotartrate and ditartrate complexes of the rare-earth elements were determined by the Bjerrum graphical method, using the method of least squares.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2203–2208, October, 1968.     

Multielemental determination in water by neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been applied to a water sample to determine the elemental concentrations. The sample was irradiated at a neutron flux of 1.2·10¹² n·cm^–2·s^–1 for two different periods followed by counting at three different decay times, using two coaxial type high-resolution Ge(Li) detectors. The dominant elements detected in the water sample are Ca, Cl, Na, Mg, and K present in levels while Co, I, Mn, Sm, and Sb are present in smaller amounts approximately on the average 0.01 ppm. Only traces of other elements such as rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water samples.     

Adult Honeybees and Beeswax as Indicators of Trace Elements Pollution in a Vulnerable Environment: Distribution among Different Apicultural Compartments

Bees in search of diet sources intensively fly within a radius of up to 3 km, encountering nectar, pollen, and water sources which are potentially contaminated. Consequently, their products can provide valuable information about potential pollution. In the current study, 27 macro and trace elements, including the most hazardous ones, were measured in bees, honey, wax, pollen, and larvae, obtained from seven explicitly industrial areas in eastern regions of Slovakia, using a validated ICP-MS method. All the analysed elements were detected at least in one matrix. The detected concentrations of toxic elements, such as Hg, Pb, and Cd were in some cases higher in wax and bee samples, compared with honey, larvae, and pollen. In particular, Pb and Hg maximum concentrations were detected in the wax samples from Poša (3193 µg/kg) and Strážske_A (90 μg/kg). In addition, adult bees accumulated more elements than larvae, while wax and adult bees seemed more suitable for monitoring macro and trace elements in the surrounding environment. Statistical analysis emphasizing bees and wax correlated Cd with the Strážske area, possibly attributed to the intensified industrial activity in this region.