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1.
Donatella Desideri Laura Feduzi Maria Assunta Meli Carla Roselli 《Microchemical Journal》2011,97(2):264-268
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 + 240,238Pu, 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. 相似文献
2.
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. 相似文献
3.
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. 相似文献
4.
N. S. Imyanitov 《Russian Journal of Inorganic Chemistry》2011,56(5):745-748
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). 相似文献
5.
Romannikov V. N. Kirik S. D. Solov'ev L. A. Shmakov A. N. Derevyankin A. Yu. Fenelonov V. B. Kholdeeva O. A. Lapina O. B. Paukshtis E. A. 《Kinetics and Catalysis》2001,42(6):857-866
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. 相似文献
6.
V. P. Antonovich N. A. Chivireva I. V. Stoyanova V. F. Zinchenko N. P. Efryushina O. N. Lasovskaya N. N. Golik 《Journal of Analytical Chemistry》2003,58(11):1042-1048
It was found that the major constituents (F– and S2–) 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 S2–), 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. 相似文献
7.
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. 相似文献
8.
Yong Sam Chung Young Ju Chung Kyung Haeng Cho Joung Hae Lee 《Journal of Radioanalytical and Nuclear Chemistry》1997,215(1):129-134
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. 相似文献
9.
R. M Sawant Poonam Verma H. R Mhatre N. K. Chaudhuri K. L. Ramakumar 《Journal of Radioanalytical and Nuclear Chemistry》2003,256(3):387-394
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. 相似文献
10.
G. Shani A. Haccoun A. Kushelevsky 《Journal of Radioanalytical and Nuclear Chemistry》1983,76(1):249-256
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. 相似文献
11.
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) = Xk, 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. 相似文献
12.
H. Papaefthymiou B. D. Symeopoulos M. Soupioni 《Journal of Radioanalytical and Nuclear Chemistry》2007,274(1):123-130
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. 相似文献
13.
E.R. Cornelissen J.S. Vrouwenvelder S.G.J. Heijman X.D. Viallefont D. Van Der Kooij L.P. Wessels 《Journal of membrane science》2007
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. 相似文献
14.
R. Moccia 《Journal of Chemical Sciences》1991,103(3):251-263
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. 相似文献
15.
Per-Olov Lwdin 《International journal of quantum chemistry》1992,41(1):213-242
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. 相似文献
16.
Dr. Morten Gotthold Vinum Laura Voigt Colby Bell Dmytro Mihrin Prof. Dr. René Wugt Larsen Prof. Dr. Kensha Marie Clark Prof. Dr. Kasper S. Pedersen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(10):2143-2147
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 CrII spontaneously affords CrIII 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. 相似文献
17.
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. 相似文献
18.
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. 相似文献
19.
M. V. Fedoseeva I. A. Revelsky E. N. Kapinus A. V. Nikoshina D. A. Burmykin A. S. Samokhin D. A. Chepelyansky A. V. Golubeva A. I. Revelsky 《Moscow University Chemistry Bulletin》2013,68(5):223-226
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. 相似文献
20.
L. Bonizzoni A. Galli G. Spinolo V. Palanza 《Analytical and bioanalytical chemistry》2009,395(7):2021-2027
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. 相似文献