Sequential determination of Am, Cm, Pu, Np and U by extraction chromatography

Environmental contamination by artificial radionuclides and the evaluation of their sources require precise isotopic analysis and accurate determination of actinide elements above all plutonium and americium. These can be achieved by alpha spectrometry or by inductively coupled plasma mass spectrometry (ICP-MS) after chemical separation. In the present work, a simple, rapid method has been developed for the sequential separation of actinide elements from aqueous solutions and their determination by alpha spectrometry. Extraction chromatography was applied to the separation of ²⁴¹Am, ²⁴⁴Cm, ^{239 + 240,238}Pu, ²³⁷Np and ^238,235,234U using microporous polyethylene supporting tri-n-octylamine as the stationary phase and hydrochloric acid with and without reducing agents as the mobile phase. Actinide in 9 M HCl solution is introduced into the anion exchange column; Pu (IV), Np (IV) and U(VI) are retained on the column while Am (III) and Cm passed through. Pu is eluted first, reductively, after which, Np and then U are eluted. The method can be applied to all aqueous solutions which do not contain strong complexing or precipitation agents for the elements considered.     

Element assessment in whole blood, serum and urine of three Italian healthy sub-populations by INAA

This research, that is a framework of a big project regarding the knowledge of human metabolism in patients affected by renal disease, is aimed to assess the levels of some selected essential (Co, Fe, K, Na, Rb, Se and Zn) and non-essential elements (Br Cr, Cs, Hg, Ni and Sb) in different biological matrices such as whole blood, serum and urine, of three Italian sub-populations.The analytical methodology involved is the Instrumental Neutron Activation Analysis (INAA), a primary analytical technique: the samples (totally 144) were irradiated in the Triga nuclear reactor at the R.C.-Casaccia ENEA for 12 h at a neutron flux of 2.6 × 10¹² n × cm^{− 2} × s^{− 1}.The results show a similar distribution for essential elements whereas quite different for non-essential elements. The statistical treatment has evidenced no differences among the samples grouping the subpopulations into unique one. In this way, the levels found can be considered “reference values” in the investigated matrices.     

Determination of trace elements in metals by atomic absorption spectrometry with introduction of solid samples into furnaces: An appraisal

The determination of trace elements in metals by atomic absorption spectrophotometry with introduction of solid samples into furnaces has been reviewed from the first paper in 1965 until the present day. The need for this type of analysis is considered along with other analytical techniques that can provide useful information. Early developments up to 1975 are presented and discussed but the main emphasis is on work undertaken during the past five years. Information is provided on homogeneity of samples, methods of calibration, accuracy, precision and limits of detection to show that this technique is the most convenient available for the determination of volatile trace elements in metals at concentrations less than 10 μg g⁻¹.     

Application of a new formulation of the periodic law to predicting the proton affinity of elements

To illustrate the efficiency of a previously proposed new formulation of the Periodic Law, the proton affinities and gas-phase basicities of 20 elements in the p- and d-blocks were predicted. These properties were considered as a function of the total number of p- or d-electrons in an atom, rather than depending on the nuclear charge or the number of outer-shell electrons. The analysis was performed block by block separately. For p elements, the kainosymmetry and additional periodicity were taken into account. Equations were deduced and then used for predicting the proton affinities and gas-phase basicities of p ⁴–p ⁶ elements (Se, Te, Po, At, and Rn) and d ²–d ¹⁰ elements (Zr, Nb, Mo, Tc, Ag, Cd, Hf, Ta, W, Re, Os, Ir, Pt, Au, and Hg).     

Physicochemical Properties of Mesoporous Mesophase Silicate Materials Formed via the Electrostatic S+I– Mechanism

The formation of the structure of a highly organized silicate mesoporous mesophase material (MMM) with hexagonal packing via the S⁺I^–reaction pathway and MMM-based aluminosilicates (Al,Si)-MMM and titanosilicates (Ti,Si)-MMM with different concentrations of the elements are considered. The structural, textural, and catalytic properties of the materials are studied.     

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.     

Some studies on3He+-activation of light elements

A series of investigations involving the use of different nuclear methods with³He⁺ ion-beams is presented for the low-level determination of some light elements (mainly B, C, N, O). As there is always a demand for interference-free techniques for the measurement of light elements, a critical evaluation of the analytical potential of the methods of interest is provided. The techniques assessed include: nuclear reaction analysis; prompt -ray spectrometry and prompt X-ray spectrometry. Of particular interest is the role played by interlemental interferences. Typical practical applications of the relevant methods for operation under routine conditions are discussed. In addition, the phenomenon of secondary excitation, leading to enhanced photon yields, in considered, for prompt X-rays observed in binary metal fluorides.     

Determination of trace and toxic elements in Korean rice CRM by INAA, ICP and AAS

Trace and toxic elements in Certified Reference Material (CRM) made of Korean rice at the Korea Research Institute of Standards and Science have been analyzed by Instrumental Neutron Activation Analysis (INAA). Data intercomparison from the measurement with those of Atomic Absorption Spectrometry (AAS) and Induced Coupled Plasma Spectrometry (ICPS) has been studied. The powdered samples were sterilized at 1.5·10⁶ rad in the bottles using a⁶⁰Co source after sieving and spiking to specific elements such as As, Cd, Cr, Cu and Hg and then the homogeneity of samples was assessed. Rice flour (SRM 1568a) and standard solutions made by the National Institute of Standards Technology (NIST) were used to construct the calibration curves for the INAA and the chemical methods, respectively. The uncertainties and concentration of constituent elements were determined and the possibility of their use for analytical quality control was considered.     

Stability constants of the aqueous mono-fluoride complexes of Pu(III) and Am(III) and their correlation with other metal ions

The stability constants of the aqueous mono-fluoride complexes of Pu(III) and Am(III) have been measured using the distribution method. A correlation of the available stability constants of fluoride complexes of trivalent actinides, up to Cf, with fundamental properties like charge and radii of the metal ion has been discussed. Good correlation within the group and as a part of other metal ions was obtained only for transplutonium elements. The reported stability constant values measured by potentiometry and the value obtained by distribution for Pu³⁺ appear to be much higher than expected from this correlation. However, a better correlation was obtained with transplutonium elements when effective charge instead of formal charge was considered for Pu³⁺ in the BSE function.     

Aerosol and air pollution study by neutron activation analysis

Thermal neutron activation analysis technique was used in air pollution and aerosol elemental content and size distribution investigations. Air pollution samples were collected on Whatman 41 paper filters which were activated along with known quantities of standards in a flux of ～10¹³ n·cm^?2·s^?1. The activity of the samples was measured with a 40 cm³ Ge(Li) detector and analyzed with the computer program JANE, which identified the isotopes and found their quantities by normalization with the standard measurement results. Correlation between the various elements, in particular those belonging to dust from the desert and those considered typical urban air pollution, is investigated.     

Hypervirial theorem and ladder operators. Recurrence relations for harmonic oscillator integrals

A second-quantization formalism combined with a hypervirial theorem is used to derive new recurrence relations for one-dimensional harmonic oscillator matrix elements. The most general case of 〈m|f(â, â⁺)|n〉 is considered, and the recurrence relations forf(â, â) = X^k, exp(?βX), and exp(?X²) are given as examples. The relations obtained are considerably simpler than those derived by using only the hypervirial theorem; comparatively, the recurrence relations presented here have the advantage of avoiding the use of the quantum mechanical sum-rules when determining initial matrix elements. The proposed procedure can be used to determine the recurrence relations for other potentials as well as to evaluate the two-center integrals.     

Neutron activation analysis and natural radioactivity measurements of lignite and ashes from Megalopolis basin,Greece

Elemental concentrations and specific activity values of natural radionuclides were measured in lignite, bottom ash and fly ash samples collected from the Megalopolis power plant A in southern Greece, using nuclear analytical techniques. The results show that the elements As, Br, Mo, Sb, Se, and U were enriched in the lignite samples, the elements Mo, Se and U in bottom ash, while fly ash samples were enriched in As, Mo, Sb, Se and U. Specific activity measurements also show that ²³⁸U (²²⁶Ra) activity values in lignite and both ash samples were high relative to the corresponding data for coal and earth crust given in the literature. As a high quantity of fly ash is produced during the operation of the lignite power plant A, this power plant should be considered as a major source of air particulate pollution and radiation to the population living in the vicinity of lignite burning power plant.     

Periodic air/water cleaning for control of biofouling in spiral wound membrane elements

The main problem during the operation of nanofiltration or reverse osmosis membrane plants is fouling of feed spacers in membrane elements due to biofouling and particulate fouling. In order to control biofouling and particulate fouling in membrane elements, both daily air/water cleaning (AWC) and daily copper sulphate dosing (CSD) were investigated and compared to a reference without daily cleaning. A pilot study was carried out for 110 days with three parallel spiral wound membrane elements; AWC, CSD and the reference which were fed by tap water enriched with a biodegradable compound (100 μg acetate-C/L). The CSD element, which combined daily copper sulphate dosing and sporadically air/water cleaning, performed best with an increase in pressure drop of 18% and a biomass concentration of 8000 pg ATP/cm² within 110 days. This was followed by the AWC element with a pressure increase of 37% and biomass concentration of 20,000 pg ATP/cm² within 110 days. The reference element showed a pressure increase of 120% within 21 days. The presented approach is considered very successful in controlling particulate fouling and biofouling, especially when air/water cleaning is combined with copper sulphate dosing.     

Theoretical methods for the calculation of the multiphoton ionisation cross-section of atoms and molecules

Some of the available theoretical methods to compute the two-photon ionisation cross-section of many-electron systems are reviewed. In particular the problems concerning the computation of (i) reliable approximations for the transition matrix elements and the excitation energies; and (ii) accurate results pertaining to the electronic continuum by the use of L² basis functions are considered.     

On rotations as special cases of unitary transformations with some applications to the theory of spin

Some problems in elementary geometry are approached from the point of view of linear algebra and generalized to the theory of linear spaces of finite or infinite dimensions having a positive definite binary product. The angle ω between two elements of the linear space is defined from the concept of length by means of the cosine-theorem. A rotation is then defined as a special case of a unitary transformation moving all elements the same angle ω, except that under certain circumstances, some elements may stay invariant. In the former case, one speaks of a rotation around an “external axis,” and in the latter case, of a rotation around an “internal axis” defined by the invariant elements. It is shown that the finite rotations U of both types may be expressed in the simple exponential form U = exp(iωm), where the “generator” m in the former case is an operator satisfying the relation m² = 1, and in the latter case, m³ = m. The structure of the group of finite rotations in the former case is clarified in some detail. As an illustration of the theory, some applications to the three- and two-dimensional spaces as well as to the theory of spin are given. The coupling between the ordinary three-dimensional rotations and the spinor transformations is considered in somewhat greater detail.     

Evidence for Non-Innocence of a β-Diketonate Ligand

β-Diketonates, such as acetylacetonate, are amongst the most common bidentate ligands towards elements across the entire periodic table and are considered wholly redox-inactive in their complexes. Herein we show that complexation of 1,1,1,5,5,5-hexafluoroacetylacetonate (hfac⁻) to Cr^II spontaneously affords Cr^III and a reduced β-diketonate radical ligand scaffold, as evidenced by crystallographic analysis, magnetic measurements, optical spectroscopy, reactivity studies, and DFT calculations. The possibility of harnessing β-diketonates as electron reservoirs opens up possibilities for new metal–ligand concerted reactivity in the ubiquitous β-diketonate coordination chemistry.     

Magnetic properties and tunnel exchange states of dimeric mixed-valence clusters with two-electron transfer

Tunnel states of dimeric mixed-valence clusters with dⁿ-dⁿ⁺² type two-electron transfer are considered. General expressions for the matrix elements of the double exchange operator are obtained taking into account the contributions of the excited states. The energy spectrum of the clusters is calculated and the magnetic properties are studied. Allowance for the dⁿ⁺¹-dⁿ⁺¹ excited states considerably affects the energy spectrum and the magnetic properties of the systems. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 6, pp. 1038–1045, November–December, 1997.     

Solvent extraction studies using tetracycline as complexing agent

The behaviour of tetracycline as an extracting agent for strontium, iodine, barium, molybdenum, technetium, zirconium, niobium, cesium, ruthenium, tellurium and uranium has been studied and the influence of the acidity of the aqueous phase upon extraction of the elements mentioned has been examined. Experiments have been made to determine whether or not the species extracted into the organic phase is the complex formed between tetracycline and the elements considered as well as to determine the time of shaking necessary so that the equilibrium between the phases is attained. As a practical application, the possibility of using the tetracycline-benzyl alcohol system for separating the fission products¹³⁷Cs,¹⁴⁰Ba,¹⁴⁰La,¹⁴¹Ce,¹⁰³Ru,⁹⁵Zr and⁹⁵Nb from each other and from uranium is presented. The same study has been made for¹³¹I,^99mTc,⁹⁹Mo,¹³²Te,²³⁹Np and uranium and the steps necessary for the separation of these elements are proposed.From a thesis submitted by I. I. L. CUNHA to the Instituto de Pesquisas Energéticas e Nucleares-University of São Paulo in partial fulfillment of the requirements for a Doctor of Science's Degree. Work supported by Comissão Nacional de Energia Nuclear.     

Rapid screening of wines for total content of F-, Cl-, Br-, and S-organic compounds

A rapid direct method for determining the total content of heteroelement-containing organic compounds in dry white wine has been developed. The method involves the solvent extraction of these compounds, the removal of extractant outside the reactor, the oxidative conversion of the total concentrate of analytes at high temperature, and the analysis of the whole absorbate volume by ion chromatography. The detection limits for different elements ranged from 10^?6 to 10^?5 g/L for 1-mL wine samples and from 10^?7 to 10^?6 g/L for 10-mL wine samples. The possibility of identifying pesticides used in viniculture based on detecting the heteroelements present in the molecule is considered.     

EDXRF quantitative analysis of chromophore chemical elements in corundum samples

Corundum is a crystalline form of aluminum oxide (Al₂O₃) and is one of the rock-forming minerals. When aluminum oxide is pure, the mineral is colorless, but the presence of trace amounts of other elements such as iron, titanium, and chromium in the crystal lattice gives the typical colors (including blue, red, violet, pink, green, yellow, orange, gray, white, colorless, and black) of gemstone varieties. The starting point for our work is the quantitative evaluation of the concentration of chromophore chemical elements with a precision as good as possible to match the data obtained by different techniques as such as optical absorption photoluminescence. The aim is to give an interpretation of the absorption bands present in the NIR and visible ranges which do not involve intervalence charge transfer transitions (Fe²⁺ → Fe³⁺ and Fe²⁺ → Ti⁴⁺), commonly considered responsible of the important features of the blue sapphire absorption spectra. So, we developed a method to evaluate as accurately as possible the autoabsorption effects and the secondary excitation effects which frequently are sources of relevant errors in the quantitative EDXRF analysis.