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1.
A method for the determination of molybdenum and tungsten in plant material using neutron activation analysis was developed. The considered reaction are: $$\begin{gathered} {}^{98}Mo(n,\gamma )^{99} Mo \hfill \\ {}^{186}W(n,\gamma )^{187} W \hfill \\ \end{gathered} $$ The separation for tungsten and molybdenum was carried out using anion exchange separation (Dowex 1×10; 200–400 mesh). Irradiation was carried out in a swimming pool reactor at a thermal flux of about 1–2×1013 n·cm?2·sec?1 for 15 hours. The samples and standard were allowed to cool for 5–6 hours before chemical processing. the high concentration of calcium in plants (up to 40 mg/g dry material), the use of hydrofluoric acid for a good absorption and quantitative recovery of tungsten led us to dissolve the samples with Ht?H2O2 mixtures containing boric acid to prevent the precipitation of fluorides. 相似文献
2.
I. P. Alimarin A. Z. Miklishanskii Yu. V. Yakovlev 《Journal of Radioanalytical and Nuclear Chemistry》1970,4(1):45-51
A method with a sensitivity of 2·10−7 to 1·10−10% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation.
The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by
passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the
resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·1013 n·cm−2·sec−1. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)3, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8
anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2
cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant. 相似文献
3.
The quantitative study of the equilibrium Pu4++Cl−⇋Pu3++1/2 Cl2 in LiCl−KCl (70–30% mol) at 455, 500, 550 and 600°C by visible and near I.R. absorption spectrophotometry allows the calculation
of the reaction's equilibrium constant, the mean thermodynamic data ΔH=27±14 kJ·mol−1 and ΔS=37±17 J·mol−1·K−1 and the standard potential of the couple
.
相似文献
4.
A. Gaudry B. Maziere D. Comar D. Nau 《Journal of Radioanalytical and Nuclear Chemistry》1976,29(1):77-87
For the simultaneous determination of many elements in small biological samples, a multi-element analysis has been developed
using neutron activation. After a 24-hr irradiation in a neutron flux of 2.5·1014 n·cm−2·sec−1 and after immediate chemical separation without cooling, it was possible to analyse 24 elements in bovine liver (NBS-SRM
1577). The separation apparatus, set up in a shielded cell can work four samples simultaneously, and its operation is fast
enough to allow the detection of radioisotopes with a half-life of about 2 hrs (165Dy,57mSr,56Mn). Amounts lower than 10−3 μg of Dy, Eu, Pr, Sm and Yb were determined. 相似文献
5.
A fast non-destructive determination of fluorine in bone samples by thermal neutron activation analysis using19F(n, γ)20F reaction was developed. About 0.1–1 g samples is irradiated for 15 sec in TRIGA MARK II reactor at a thermal neutron flux
of 5·1011 n·cm−2·sec−1. After 15–25 sec cooling, the 1633 KeV20F activity (T=11.2 sec) is counted for 15 sec with a Ge(Li) spectrometer. A standard sample is prepared by mixing CaF2 and CaCO3 powders. The interference from23Na(n, α)20F is corrected by employing24Na 2754 KeV double escape peak activities in samples and the20F/24Na peak area ratio observed previously for pure Na2CO3 powder. The precision is 7% for a bone sample containing 1020 ppm F and the sensitivity is about 10 ppm F. 相似文献
6.
I. P. Alimarin Yu. V. Jakovlev A. Z. Miklishansky N. N. Dogadkin O. V. Stepanets 《Journal of Radioanalytical and Nuclear Chemistry》1968,1(2):139-145
Radioactivation analysis is the only method which allows the determination of individual rare earth element impurities in
rare earth elements of high purity. The determination of dysprosium, europium, samarium and gadolinium in yttrium oxide is
complicated by the short half-life of165Dy (138 min.) and by the difficulty of separating traces of these elements from the matrix. A chromatographic method has been
developed, for the separation of traces of Dy, Eu, Sm and Gd from ytrium, on a column packed with anion exchangerAV-17, by means of elution with 0.1N and 0.3M solutions of EDTA-sodium salt, followed by the separation of the mixture of the rare earth impurities on a microcolumn of
cation exchangerKU-2, using a 0.17M solution of ammonium α-hydroxyisobutyrate as the eluent. The sensitivity of the determination of Dy, in the case of irradiating
10 mg of Y2O3 with a flux of 1.2·1013 n·cm−2·sec−1 for 5 min. was 1·10−7%; the corresponding values for Sm, Eu and Gd, when irradiating a 100 mg sample of Y2O3 for 20 hours with the same flux, were 2·10−7%, 1·10−8% and 5·10−6%, respectively. 相似文献
7.
From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium
\textCs + ( \textaq ) + \textA - ( \textaq ) + 1( \textnb )\underset \rightleftharpoons 1·\textCs + ( \textnb ) + \textA - ( \textnb ) {\text{Cs}}^{ + } \left( {\text{aq}} \right) + {\text{A}}^{ - } \left( {\text{aq}} \right) + {\mathbf{1}}\left( {\text{nb}} \right)\underset {} \rightleftharpoons {\mathbf{1}}\cdot{\text{Cs}}^{ + } \left( {\text{nb}} \right) + {\text{A}}^{ - } \left( {\text{nb}} \right) taking place in the two-phase water-nitrobenzene system (A− = picrate, 1 = dibenzo-21-crown-7; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K
ex (1·Cs+, A−) = 4.4 ± 0.1. Further, the stability constant of the 1·Cs+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Cs+) = 6.3 ± 0.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the resulting cationic
complex species 1·Cs+ was solved. 相似文献
8.
A procedure for the determination of chromium in blood has been developed with a sensitivity of 5×10−3 μg Cr. Dried blood was irradiated with a neutron flux of 1012 n·cm−2·sec−1 in the VVRS reactor for 4 weeks, then the sample was mineralized and the chromium isolated by extraction as perchromic acid.
The determination of the chromium content was accomplished by measuring the 0.32 MeV gamma energy of51Cr. In order to make correction for the interfering reaction54Fe(n,α)51Cr, the formation of chromium from high-purity iron was investigated. The chromium content of the blood samples was between
1.03×10−2 and 5.2×10−2 ppm Cr. 相似文献
9.
Thato N. Mtshali Walter Purcell Hendrik G. Visser Steven S. Basson 《Transition Metal Chemistry》2008,33(4):481-491
The kinetics of the reaction between [ReN(H2O)-(CN)4]2− with different κ2
N,O-donor ligands (quin− and 2,3-dipic−, respectively) have been studied in the pH 4–12 range in aqueous solution. Two consecutive reaction steps with the formation
of the [ReN(η1-quin)(CN)4]3− and [ReN(μ2-quin) (CN)3]2− complexes, respectively, were spectrophotometrically observed and kinetically investigated. The same reaction mechanism is
proposed for these two ligands. The first fast reaction (for quin−) is attributed to the aqua substitution of [ReN(H2O)(CN)4]2− with forward and reverse rate constants of 1.96(5) × 10−1 M−1 s−1 and 5.6(3) × 10−2 s−1, while a rate of 2.64(3) M−1 s−1 was observed for the reaction between the conjugate base [ReN(OH)(CN)4]3− and quin− at 40.2 °C. Due to small absorbance changes, it was difficult to obtain any good quality data for the fast reactions for
2,3-dipic−. The second, slower reaction is attributed to cyano substitution with rate constants (k
3
K
1) of 4.17(4) × 10−3 for quin− and 4.68(7) × 10−3 M−1 s−1 for 2,3-dipic−, at 80.02 °C, respectively. The acid dissociation constant for the aqua complex was spectrophotometrically determined as
11.58(3) and 11.54(2) and kinetically as 11.51(8) and 11.41(1), at 80.4 °C, respectively. Negative values of −83.5(2) and −144.1(2) J K−1 mol−1 as well as the of 71.4(3) and 47.3(3) kJ mol−1, for the slow quin− and 2,3-dipic− reactions, respectively, point to an ordered transition state where bond formation is responsible for the major driving force
of the reaction. The and for the fast forward reaction of quin− is indicative of expected associative activation in the transition state.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
A collimated neutron beam capable of providing a thermal neutron flux of 4.75·107 n·cm−2·sec−1 has been used to analyze alloy samples of 1–5 g during relatively short irradiation times of 30 min by the use of neutron
capture gamma-ray spectrometry. The analyses were performed by using a mathematical treatment that relates the count ratio
of every constituent present in the matrix with the concentration and thus it requires no standards. The technique was applied
to the analysis of steel and gold alloy samples. Errors ranged from 0.8%–10%. 相似文献
11.
Marco Giardiello Mauro Botta Mark P. Lowe 《Journal of inclusion phenomena and macrocyclic chemistry》2011,71(3-4):435-444
Two DOTA-based proligands bearing a pendant diphenylphosphinamide 4a and 4b were synthesised. Their Eu(III) complexes exhibit sensitised emission when excited at 270 nm via the diphenylphosphinamide chromophore. Hydration states of q = 1.5 were determined from excited state lifetime measurements (Eu.4a $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 2. 1 4 \,{\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 0. 6 4 \,{\text{ms}}^{ - 1} $ ; Eu.4b $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 2. 6 7\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 1. 1 8 \,{\text{ms}}^{ - 1} $ ). In the presence of human serum albumin (HSA) (0.1 mM Eu.4a/b, 0.67 mM HSA, pH 7.4) q = 0.4 for Eu.4a ( $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 1. 3 4\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 0. 7 5\, {\text{ms}}^{ - 1} $ ) and q = 0.6 for Eu.4b ( $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 1. 8 3\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 1.0 5 \,{\text{ms}}^{ - 1} $ ). Relaxivites (pH 7.4, 298 K, 20 MHz) of the Gd(III) complexes in the absence and presence of HSA (0.1 mM Gd.4a/b, 0.67 mM HSA) were: Gd.4a (r 1 = 7.6 mM?1s?1 and r 1 = 11.7 mM?1s?1) and Gd.4b. (r 1 = 7.3 mM?1s?1 and r 1 = 16.0 mM?1s?1). These relatively modest increases in r 1 are consistent with the change in inner-sphere hydration on binding to HSA shown by luminescence measurements on Eu.4a/b. Binding constants for HSA determined by the quenching of luminescence (Eu) and enhancement of relaxivity (Gd) were Eu.4a (27,000 M?1 ± 12%), Eu.4b (32,000 M?1 ± 14%), Gd.4a (21,000 M?1 ± 15%) and Gd.4b (26,000 M?1 ± 15%). 相似文献
12.
The use of 2.8 MeV neutrons produced by the D(d, n)3He reaction should be taken into consideration in some applications of radioactivation analysis. The low number of elements
activable by these neutrons makes possible to minimize the matrix interference and the background below the characteristic
photopeaks. The very low dead-time of the spectrometric measurements permits the use of the maximum neutron flux available
now and in the future. The purpose of this paper is to define experimentally the sensitivity of determination for the 16 main
elements activable with a 400 keV Van de Graaff accelerator at a 2.8 MeV neutron flux of 2·106 n·cm−2·sec−1 on the sample. 相似文献
13.
A novel sensor for the determination of nitrite anion () was fabricated by electrodeposition of toluidine blue. The sensor exhibited good catalytic activity toward the electrochemical
oxidation of nitrite. Amperometry was carried out to determine the concentration of . A linear response in the range from 1.0×10−7 to 1.52×10−5 M with a substantially low detection limit of 5×10−8 M (S/N=3) was obtained. The proposed sensor had a feature of high sensitivity of 4.7×105 μA M−1 cm−2. The possible interference from several common ions was tested. This sensor was applied to the amperometric determination
of nitrite in food samples, and the results were consistent with those obtained with the standard spectrophotometric procedure. 相似文献
14.
P. K. Nayak B. Wierczinski S. Lahiri 《Journal of Radioanalytical and Nuclear Chemistry》2008,278(1):179-184
Representative banded iron-formations (BIFs) from various locations of the eastern Indian geological belt were investigated
by instrumental neutron activation analysis (INAA). After pre-concentration, irradiation was carried out using a neutron flux
of 5.1·1016 m−2·s−1, 1.0·1015 m−2·s−1 and 3.7·1015 m−2s−1, with thermal, epi-thermal and fast neutrons, respectively. The activities in these samples were measured by a HPGe detector.
Ten rare-earth elements, such as La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu, have been qualitatively identified and quantitatively
estimated in these samples. The present investigation is an example of employing a pre-concentration method for high iron-containing
ores prior to neutron activation analysis. 相似文献
15.
The heat of solution of GaCl3 and heats of dilution of single GaCl3 solutions in water and of mixed GaCl3−HCl solutions in HCl solutions (with a fixed HCl concentration of 0.1337 mol-kg−1 HCl) up to 4 mol-kg−1 GaCl3 were measured at 25°C. While in the acid solutions hydrolysis is suppressed to below 0.5% of total gallium concentration,
the measurements in water allow evaluation of the effect of hydrolysis on the relative enthalpy. The Pitzer interaction model
for excess properties of aqueous electrolytes was used to interpret the change in relative enthalpy with concentration. Pitzer
parameters were derived by statistical inference using ridge regression. Their physical significance is supported by the heat
of solution data. The measurements yield the following results for standard heats of formation and Pitzer parameters for the
relative molar enthalpy at 25°C:
With these parameters the overall variance in the partial molar heat of solution at infinite dilution, extrapolated from the
present experiments, is minimized to 0.35 kJ2-mol−2, while the experimental apparent molar heats of dilution are reproduced on average within 2.7 kJ-mol−1. 相似文献
16.
B. Vialatte 《Journal of Radioanalytical and Nuclear Chemistry》1971,8(2):269-276
The determination of lithium by measuring7Be, produced by proton or deuteron activation, has been studied. The extent of interference from boron or beryllium, which
also form7Be, was measured. The calculated sensitivity limits when activating for one hour with 10μA beams of 14 MeV protons or 25 MeV
deuterons are, for lithium, 1·10−1 and 2.5·10−2 ppm and for boron, 2·10−1 and 1·10−1 ppm, respectively.
相似文献
17.
Nine new μ-oxamido-bridged copper(II)-lanthanide(III)-copper(II) heterotrinuclear complexes described by the overall formula
Cu2(dmoxae)2Ln(NO3)3 {Ln = Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er; dmoxae = N,N′-bis[2-(dimethylamino)ethyl]oxamido dianions} have been synthesized by the strategy of ‘complex as ligand’, and characterized
by elemental analyses, molar conductivity measurements, i.r. and electronic spectral studies. The variable-temperature susceptibility
(2–300 K), e.s.r. measurements, and studies of the Cu2(dmoxae)2Gd(NO3)3 complex have revealed that the central gadolinium(III) and terminal copper(II) ions are ferromagnetically coupled with the
exchange integral J(Cu-Gd) = +2.1 cm−1, while an antiferromagnetic coupling is detected between the terminal copper(II) ions with J′(Cu-Cu)=−0.36 cm−1, on the basis of the spin Hamiltonian operator
.
A plausible mechanism for the ferromagnetic coupling between copper(II) and gadolinium(III) is discussed in terms of spin
polarization. 相似文献
18.
Donald A. Palmer Pascale Bénézeth Caibin Xiao David J. Wesolowski Lawrence M. Anovitz 《Journal of solution chemistry》2011,40(4):680-702
Results of solubility experiments involving crystalline nickel oxide (bunsenite) in aqueous solutions are reported as functions
of temperature (0 to 350 °C) and pH at pressures slightly exceeding (with one exception) saturation vapor pressure. These
experiments were carried out in either flow-through reactors or a hydrogen-electrode concentration cell for mildly acidic
to near neutral pH solutions. The results were treated successfully with a thermodynamic model incorporating only the unhydrolyzed
aqueous nickel species (viz., Ni2+) and the neutrally charged hydrolyzed species (viz., Ni(OH)20)\mathrm{Ni(OH)}_{2}^{0}). The thermodynamic quantities obtained at 25 °C and infinite dilution are, with 2σ uncertainties:
log10Ks0o = (12.40 ±0.29),\varDeltarGmo = -(70. 8 ±1.7)\log_{10}K_{\mathrm{s0}}^{\mathrm{o}} = (12.40 \pm 0.29),\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = -(70. 8 \pm 1.7) kJ⋅mol−1;
\varDeltarHmo = -(105.6 ±1.3)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = -(105.6 \pm 1.3) kJ⋅mol−1;
\varDeltarSmo = -(116.6 ±3.2)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} =-(116.6 \pm 3.2) J⋅K−1⋅mol−1;
\varDeltarCp,mo = (0 ±13)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = (0 \pm 13) J⋅K−1⋅mol−1; and log10Ks2o = -(8.76 ±0.15)\log_{10}K_{\mathrm{s2}}^{\mathrm{o}} = -(8.76 \pm 0.15);
\varDeltarGmo = (50.0 ±1.7)\varDelta_{\mathrm{r}}G_{m}^{\mathrm{o}} = (50.0 \pm 1.7) kJ⋅mol−1;
\varDeltarHmo = (17.7 ±1.7)\varDelta_{\mathrm{r}}H_{m}^{\mathrm{o}} = (17.7 \pm 1.7) kJ⋅mol−1;
\varDeltarSmo = -(108±7)\varDelta_{\mathrm{r}}S_{m}^{\mathrm{o}} = -(108\pm 7) J⋅K−1⋅mol−1;
\varDeltarCp,mo = -(108 ±3)\varDelta_{\mathrm{r}}C_{p,m}^{\mathrm{o}} = -(108 \pm 3) J⋅K−1⋅mol−1. These results are internally consistent, but the latter set differs from those gleaned from previous studies recorded in
the literature. The corresponding thermodynamic quantities for the formation of Ni2+ and Ni(OH)20\mathrm{Ni(OH)}_{2}^{0} are also estimated. Moreover, the Ni(OH)3 -\mathrm{Ni(OH)}_{3}^{ -} anion was never observed, even in relatively strong basic solutions (mOH - = 0.1m_{\mathrm{OH}^{ -}} = 0.1 mol⋅kg−1), contrary to the conclusions drawn from all but one previous study. 相似文献
19.
Products of radical combination from the free-radical buffer system \documentclass{article}\usepackage{amssymb}\pagestyle{empty}\begin{document}$${{\rm R}^{\rm .} + {\rm R}^{\rm '} {\rm I}\mathop {\leftrightharpoons}\limits^{{\rm K}_{{\rm RR}}}{\rm RI} + {\rm R}^{'}}$$\end{document}. have been analyzed for the two cases, R = Me, R′ = iPr and R = Et, R′ = iPr. Results are consistent with the previously examined system where R = Me, R′ = Et, and give a value of kP for iPr· combination of 108.6±1.1 M?1 sec?1. 相似文献
20.
S. X. Xiao J. J. Zhang X. Li L. J. Ye H. W. Gu N. Ren 《Journal of Thermal Analysis and Calorimetry》2010,102(2):813-817
A ternary binuclear complex of dysprosium chloride hexahydrate with m-nitrobenzoic acid and 1,10-phenanthroline, [Dy(m-NBA)3phen]2·4H2O (m-NBA: m-nitrobenzoate; phen: 1,10-phenanthroline) was synthesized. The dissolution enthalpies of [2phen·H2O(s)], [6m-HNBA(s)], [2DyCl3·6H2O(s)], and [Dy(m-NBA)3phen]2·4H2O(s) in the calorimetric solvent (VDMSO:VMeOH = 3:2) were determined by the solution–reaction isoperibol calorimeter at 298.15 K to be
\Updelta\texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2phen·H2O(s), 298.15 K] = 21.7367 ± 0.3150 kJ·mol−1,
\Updelta\texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [6m-HNBA(s), 298.15 K] = 15.3635 ± 0.2235 kJ·mol−1,
\Updelta\texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [2DyCl3·6H2O(s), 298.15 K] = −203.5331 ± 0.2200 kJ·mol−1, and
\Updelta\texts H\textmq \Updelta_{\text{s}} H_{\text{m}}^{\theta } [[Dy(m-NBA)3phen]2·4H2O(s), 298.15 K] = 53.5965 ± 0.2367 kJ·mol−1, respectively. The enthalpy change of the reaction was determined to be
\Updelta\textr H\textmq = 3 6 9. 4 9 ±0. 5 6 \textkJ·\textmol - 1 . \Updelta_{\text{r}} H_{\text{m}}^{\theta } = 3 6 9. 4 9 \pm 0. 5 6 \;{\text{kJ}}\cdot {\text{mol}}^{ - 1} . According to the above results and the relevant data in the literature, through Hess’ law, the standard molar enthalpy of
formation of [Dy(m-NBA)3phen]2·4H2O(s) was estimated to be
\Updelta\textf H\textmq \Updelta_{\text{f}} H_{\text{m}}^{\theta } [[Dy(m-NBA)3phen]2·4H2O(s), 298.15 K] = −5525 ± 6 kJ·mol−1. 相似文献