共查询到20条相似文献,搜索用时 15 毫秒
1.
The electrophoretic mobility change of desferrioxamine B (DFO) was monitored by UV absorption spectrophotometry upon increasing the thorium(IV) concentration in the background electrolyte at two acidities ([HClO4]Tot = 0.0316 and 0.0100 M). These data enabled to assess the speciation model and to determine the equilibrium constant of [Th(DFO)H2]3+ at fixed ionic strength (I = 0.1 M (H,Na)ClO4). Affinity capillary electrophoresis (ACE) turned out to be most helpful in identifying the complexed species by ascertaining its charge and protonation state. The assignment of the correct stoichiometry relied on the reliable estimation of the electrophoretic mobility by assuming similar hydrodynamic radii for (DFO)H4+ and the chelate. The value of the apparent equilibrium constant (log β112 = 38.7 ± 0.4) obtained by ACE compares favorably well with those reported in the literature for thorium and a range of other metal ions, according to a linear free-energy relationship. This method is useful for studying metal-ligand binding equilibria and provides valuable information for further modelling the behavior of tetravalent actinides under environmental conditions. Structural information about the prevalent solution species in acidic conditions was gained by DFT calculations, confirming the bishydroxamato coordination mode of Th4+ by the diprotonated ligand. 相似文献
2.
Summary Stoichiometric stability constants of Cu(II), Ni(II), Zn(II), Co(II), UO2(II) and Th(VI) phthalate have been determined by paper electrophoresis. Phthalic acid (0.005 mol dm−3) was added to the background electrolyte: 0.1 mol dm−3 HClO4. The proportions of C6H5C2O
4
−
and C6H4C2O
4
=
were varied by changing the pH of the electrolyte. These anions yielded the complexes, Cu C6H5C2O
4
+
, Cu C6H4C2O4, Zn C6H5C2O
4
+
, Co C6H5C2O
4
+
, Ni C6H5C2O
4
+
, UO2 C6H5C2O
4
+
, UO2 (C6H4C2O4)
2
=
and Th (C6H4C2O4)2 whose stability constants are found to be 103.0, 104.7, 102.6, 102.5, 102.3, 103.5, 1012.6 and 1013.4 respectively (μ=0.1, temp 40°C). 相似文献
3.
Jeremy Petit Valérie Geertsen Catherine Beaucaire Moncef Stambouli 《Journal of chromatography. A》2009,1216(18):4113-4120
Nuclear energy development has raised new issues like radionuclides biogeochemistry. The modelling of their biochemical properties involves the accurate determination of thermodynamical data, like stability constants. This can be achieved by using hyphenated capillary electrophoresis (CE)–ICPMS and the method was applied successfully on 1:1 lanthanum–oxalate and uranyl–oxalate complexes. Several significant steps are discussed: choice of analytical conditions, electrophoretic mobility calculation, mathematical treatment of experimental data by using linear regressions, ligand concentration and ionic strength corrections. The following values were obtained with a good precision for lanthanum–oxalate and uranyl–oxalate complexes: log(K°(LaOxa+)) = 6.10 ± 0.10 and log(K°(UO2Oxa)) = 6.40 ± 0.30, respectively, at infinite dilution. These values are consistent with the literature data, showing CE–ICPMS potential for metal complexes stability constants determination. 相似文献
4.
G. Meinrath 《Journal of Radioanalytical and Nuclear Chemistry》1996,211(2):349-362
There are very few examples in nature for U(VI) compounds with carbonate ligands other than the well known tricarbonates. Especially examples of U(VI) dicarbonato compounds are nearly completely missing. Even in aqueous solutions, the dicarbonato complex was found as a species of minorimportance only. On the basis of structural data on the ligands H2O and carbonate as well as the available data on U(VI) coordination compounds, steric requirements of equatorial coordination are studied for aqueous solution species. A pentagonally coordinated monocarbonato species [UO2CO3(H2O)3] is found as the most likely coordination. For the dicarbonato species, hexagonally coordinated [UO2(CO3)2(H2O)2] with D2h symmetry is found as most probable structure. Possible causes of the instability of U(VI) dicarbonato species are discussed. 相似文献
5.
Summary Th(IV), UO2(II), Ce(III) and La(III) chelates with 3-benzamidorhodanine and its derivatives have been investigated potentiometrically in 0.1M KCl and 20% (v/v) ethanol-water medium. The stability of the formed complexes increases in the order Th(IV)>UO2(II)>Ce(III)>La(III). For the same metal ion, the stability of the chelates is found to increase with decreasing temperature, ionic strength, dielectric constant of the medium and by increasing the electron repelling property of the substituent. The thermodynamic parameters (G, H and S) for complexation are evaluated and discussed. The formation of the complexes has been found to be spontaneous, exothermic and entropically favourable.
Thermodynamik von substituiertem Rhodanin II: Binäre Komplexe von Th(IV), UO2(II), Ce(III) und La(III) mit 3-Benzamidorhodanin und seinen Derivaten
Zusammenfassung Th(IV)-, UO2(II)-, Ce(III)- und La(III)-Chelate mit 3-Benzamidorhodanin und seinen Derivaten wurden in 0.1M KCl und 20% (/) Ethanol-Wasser potentiometrisch untersucht. Die Stabilität der gebildeten Komplexe steigt in der Reihenfolge Th(IV)>UO2(II)>Ce(III)>La(III). Für ein- und dasselbe Metallion steigt die Stabilität der Chelate mit sinkender Temperatur, Ionenstärke und Dielektrizitätskonstante des Mediums und mit steigender Elektronenabstoßungsfähigkeit des Substituenten. Die thermodynamischen Parameter (G, H und S) für die Komplexbildungsreaktion werden bestimmt und diskutiert. Die Bildung der Komplexe erweist sich als spontan, exotherm und entropisch begünstigt.相似文献
6.
Complexation of divalent cations (Mg2+, Co2+, Ni2+, Cu2+, Cd2+) by selenate ligand was studied by ACE (UV indirect detection) in 0.1 mol/L NaNO3 ionic strength solutions at various temperatures (15, 25, 35, 45 and 55°C). For each solution, a unique peak was observed as a result of a fast equilibrium between the free ion and the complex (labile systems). The migration time corresponding to this peak changed as a function of the solution composition, namely the free and complexed metal concentrations, according to the complexation reactions. The results confirmed the formation of a unique 1:1 complex for each cation. The thermodynamic parameters were fitted to the experimental data at 0.1 mol/L ionic strength: (25°C) = ?(6.5 ± 0.3), ?(7.5 ± 0.3), ?(7.7 ± 0.3), ?(7.7 ± 0.3), and –(8.1 ± 0.3) kJ/mol and = 2.5 ± 0.2, 4.7 ± 0.4, 4.5 ± 0.6, 8.4 ± 1.1, and 7.2 ± 0.6 kJ/mol for M2+ = Mg2+, Co2+, Ni2+, Cu2+, and Cd2+, respectively. Complexes with alkaline earth and transition metal cations could be distinguished by their relative stabilities. The effect of the ionic medium was treated using the specific ion interaction theory and the thermodynamic parameters at infinite dilution were compared to previously published data on metal–selenate, metal–sulfate, and metal–chromate complexes. 相似文献
7.
P. S. Berdonosov P. Schmidt O. A. Dityat'yev V. A. Dolgikh P. Lightfoot Michael Ruck 《无机化学与普通化学杂志》2004,630(10):1395-1400
Pale pink crystals of Nd2(SeO3)2(SeO4) · 2H2O were synthesized under hydrothermal conditions from H2SeO3 and Nd2O3 at about 200 °C. X‐ray diffraction on powder and single‐crystals revealed that the compound crystallizes with the monoclinic space group C 2/c (a = 12.276(1) Å, b = 7.0783(5) Å, c = 13.329(1) Å, β = 104.276(7)°). The crystal structure of Nd2(SeO3)2(SeO4) · 2H2O is an ordered variant of the corresponding erbium compound. Eight oxygen atoms coordinate the NdIII atom in the shape of a bi‐capped trigonal prism. The oxygen atoms are part of pyramidal (SeIVO3)2? groups, (SeVIO4)2? tetrahedra and water molecules. The [NdO8] polyhedra share edges to form chains oriented along [010]. The selenate ions link these chains into layers parallel to (001). The layers are interconnected by the selenite ions into a three‐dimensional framework. The dehydration of Nd2(SeO3)2(SeO4) · 2H2O starts at 260 °C. The thermal decomposition into Nd2SeO5, SeO2 and O2 at 680 °C is followed by further loss of SeO2 leaving cubic Nd2O3. 相似文献
8.
《Journal of Coordination Chemistry》2012,65(17):2743-2749
The interaction of uranyl with meso-tetraphenylporphyrin and its para-substituted derivatives (H2t(4-X)pp, X : H, Br, Cl, CH(CH3)2, OCH3, CH3) in chloroform produced 1 : 1 sitting-atop (SAT) complexes ((uranyl)H2t(4-X)pp). Formation constants were calculated by computer fitting of complex absorbance versus mole ratio data to appropriate equations and found to decrease with temperature increase. Thermodynamic parameters, ΔG 0, ΔH 0 and ΔS 0 were obtained. The formation constants vary with changing of the substituent on the aryl rings of H2t(4-X)pp in the following order: (uranyl)H2t(4-OCH3)pp?>?(uranyl)H2t(4-CH3)pp?>?(uranyl)H2t(4-CH(CH3)2)pp?>?(uranyl)H2tpp?>?(uranyl)H2t(4-Br)pp?>?(uranyl)H2t(4-Cl)pp. 相似文献
9.
E. A. Gomaa M. A. Ghandour R. A. Abo-Doma 《Monatshefte für Chemie / Chemical Monthly》1985,116(1):33-42
The polarographic behaviour of uranyl ion in maleic acid solution shows two reduction waves. The half wave potential of the first wave is shifted to more negative values in contrast to that of the second wave, which is shifted to less negative potentials on increase of thepH of the solution. The first wave represents the reduction of the 1:1 uranyl-maleate complex, while the second wave represents the reduction of the 1:2 complex. The presence of 1:1 and 1:2 complexes is supported by spectrophotometric and conductometric methods. The stability constants were also determined and the reduction mechanism is discussed.
Das polarographische Verhalten von Uranyl-Ionen in Maleinsäure- und Maleat-Puffer-Lösungen
Zusammenfassung Die polarographische Kurve von Uranyl-Ionen in Maleinsäurelösung zeigt zwei Reduktionswellen. Das Halbwellenpotential der ersten Welle verschiebt sich bei ansteigendempH der Lösung zu negativeren Werten, im Gegensatz zur zweiten Welle, die eine positive Verschiebung zeigt. Die erste Welle repräsentiert die Reduktion des 1:1-Uranyl-Maleat-Komplexes, die zweite Welle hingegen die Reduktion des 1:2-Komplexes. Die Präsenz von 1:1- und 1:2-Komplexen wird auch durch spektrophotometrische und konduktometrische Messungen erhärtet. Die Stabilitätskonstanten wurden bestimmt, der Mechanismus der Reduktion wird diskutiert.相似文献
10.
Liu Q Inoue T Kirchhoff JR Huang C Tillekeratne LM Olmstead K Hudson RA 《Journal of chromatography. A》2004,1033(2):349-356
The separation of two highly negatively charged enantiomeric organic disulfates containing two chiral centers was investigated by capillary electrophoresis using cyclodextrin based chiral selectors added to the run buffer. The optimum separation for the enantiomers was achieved in less than 3 min at 25 degrees C with a run buffer of 10 mM glycine pH 2.4 and 5 mM QA-beta-CD, which is a positively charged quaternary ammonium beta-cyclodextrin derivative. The method resulted in baseline resolution, excellent linearity, and highly reproducible migration times allowing facile evaluation of the enantiomeric purity of the individual isomers. Detection limits for the enantiomeric pair were determined to be 0.3 ng/microl (S/N = 3). The nature of the selector-enantiomer interaction and a quantitative measurement of the apparent stability constants that governed chiral discrimination of the enantiomers with QA-beta-CD were also investigated by UV-Vis spectroscopy and electrospray ionization mass spectrometry. 相似文献
11.
Fangting Chi Xiaolin Wang Jie Xiong Sheng Hu 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(3):1331-1340
PVA functionalized with vinylphosphonic acid was prepared as a new adsorbent for uranyl (VI) adsorption from aqueous solutions. The vinylphosphonic acid was cografted onto PVA fibers by preirradiation grafting technique. The adsorbent were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorbent was observed to possess a fibrous structure and was bonded with phosphonic acid groups successfully. The adsorbent was used for the adsorption of low levels uranyl (VI) ions from aqueous solutions. The influence of analytical parameters including pH, adsorption time, amount of adsorbent, metal ion concentration, and temperature were investigated on the recovery of uranyl (VI) ion in aqueous solution. The maximum adsorption capacity (32.1 mg g?1) and fast equilibrium time (30 min) were achieved at pH of 4.5 at room temperature. Thermodynamic parameters (ΔH° = 2.695 kJ mol?1; ΔS° = 31.15 J mol?1 K?1; ΔG° = ?6.748 kJ mol?1) show the adsorption of an exothermic process and spontaneous nature, respectively. The possible coordination mechanism was illustrated. Adsorption and desorption coexist in aqueous solutions and then the system becomes equilibrium. 相似文献
12.
《Journal of Coordination Chemistry》2012,65(5):531-536
Complexation between cerium(IV) and carbonate ions in aqueous solution has been studied by UV/Visible absorption spectroscopy, 17O NMR spectroscopy and potentiometric titration, and it is shown that in dilute solutions at pH 8.8 and 10, both 1?:?1 and 1?:?2 (metal?:?ligand) complexes are formed. This contrasts with the behaviour of the corresponding Th(IV) complex, where the dominant species is the pentacarbonato complex. From the NMR spectra, it is suggested that these species involve bidentate binding of carbonate ion by the metal, while potentiometric data provided accurate formation constants and indicated the dominant species to be the 1?:?2 complex. 相似文献
13.
Te(IV) can be separated from Te(VI), Se(IV) and Se(VI) by adsorption of Te(IV) on a DEAE-cellulose column from a mixed 1M hydrochloric acid-acetic acid solution (1:9, v/v). This allows a selective separation of Te (IV) from the other three species in widely different mole ratios. 相似文献
14.
15.
Gallignani M Valero M Brunetto MR Burguera JL Burguera M Petit de Peña Y 《Talanta》2000,52(6):1015-1024
In this study a flow injection (FI) system used in conjunction with hydride generation (HG), atomic absorption spectrometry (AAS) and microwave (MW) aided pre-reduction of selenite (Se(IV)) to selenate (Se(IV)) with HCl:HBr has been developed in order to differentiate both inorganic selenium species. As full control of the MW reduction step is possible, the experimental approach allows the use of milder acidic conditions (10% v/v of HCl and HBr) than those conventionally accomplished with hydrochloric acid alone (≥50% v/v). Experimental parameters were optimized by the univariate optimization method. In either case, the linear range was from 1.0 to 30 μg l−1. The detection limits based on 3σ of the blank signal were 0.25 μg l−1 for Se(IV) and 0.30 μg l−1 for Se(VI). The reproducibility, about 3% RSD and recoveries of different amounts of Se(VI) and Se(IV) added to water and orange juice samples (97–103%) were good. The main advantage of the proposed method is that the sequential determination of Se(IV) and Se(VI) is performed at a high sampling frequency (ca. 50 samples per h) in a closed system without Se losses, and with a minimum sample waste, operator attention, and sample manipulation. 相似文献
16.
J.L. Burguera P. Carrero M. Burguera C. Rondon M.R. Brunetto M. Gallignani 《Spectrochimica Acta Part B: Atomic Spectroscopy》1996,51(14):1837-1847
An on-line flow injection system has been developed for the selective determination of Se(IV) and Se(VI) in citric fruit juices and geothermal waters by hydride generation atomic absorption spectrometry with microwave-aided heating prereduction of Se(VI) to Se(IV). The samples and the prereductant solutions (4 mol l−1 HCl for Se(IV) and 12 mol l−1 HCl for Se(VI)) which circulated in a closed-flow circuit were injected by means of a time-based injector. This mixture was displaced by a carrier solution of 1% v/v of hydrochloric acid through a PTFE coil located inside the focused microwave oven and mixed downstream with a borohydride solution to generate the hydride. The linear ranges were 0–120 and 0–100 μg l−1 of Se(IV) and Se(VI), respectively. The detection limits were 1.0 μg l−1 for Se(IV) and 1.5 μg l−1 for Se(VI). The precision (about 2.0–2.5% RSD) and recoveries (96–98% for Se(IV) and 94–98% for Se(VI)) were good. Total selenium values were also obtained by electrothermal atomic absorption spectrometry which agreed with the content of both selenium species. The sample throughput was about 50 measurements per hour. The main advantage of the method is that the selective determination of Se(IV) and Se(VI) in citric fruit juices and geothermal waters is performed in a closed system with a minimum sample manipulation, exposure to the environment, minimum sample waste and operator attention. 相似文献
17.
Violaine Philippini Jean Aupiais Thomas Vercouter Christophe Moulin 《Electrophoresis》2009,30(20):3582-3590
Ca2+ complexation by both sulfate and selenate ligands was studied by CE. The species were observed to give a unique retention peak as a result of a fast equilibrium between the free ions and the complexes. The change in the corresponding retention time was interpreted with respect to the equilibrium constant of the complexation reaction. The results confirmed the formation of CaSO4(aq) and CaSeO4(aq) under our experimental conditions. The formation data were derived from the series of measurements carried out at about 15, 25, 35, 45 and 55°C in 0.1 mol/L NaNO3 ionic strength solutions, and in 0.5 and 1.0 mol/L NaNO3 ionic strength solutions at 25°C. Using a constant enthalpy of reaction enabled to fit all the experimental data in a 0.1 mol/L medium, leading to the thermodynamic parameters: ΔrG0.1M(25°C)=?(7.59±0.23) kJ/mol, ΔrH0.1 M=5.57±0.80 kJ/mol, and ΔrS0.1 M(25°C)=44.0±3.0 J mol?1 K?1 for CaSO4(aq) and ΔrG0.1 M(25°C)=?(6.66±0.23) kJ/mol, ΔrH0.1 M=6.45±0.73 kJ/mol, and ΔrS0.1 M(25°C)=44.0±3.0 J mol?1 K?1 for CaSeO4(aq). Both formation reactions were found to be endothermic and entropy driven. CaSO4(aq) appears to be more stable than CaSeO4(aq) by 0.93 kJ/mol under these experimental conditions, which correlates with the difference of acidity of the anions as expected for interactions between hard acids and hard bases according to the hard and soft acids and bases theory. The effect of the ionic medium on the formation constants was successfully treated using the Specific ion Interaction Theory, leading to significantly different binary coefficients mol/kg?1 and mol/kg?1 相似文献
18.
This paper deals with determination of selenium and analysis of its speciation in some Italian mineral waters. Selenium was determined by differential pulse cathodic stripping voltammetry (DPCSV) even if square wave cathodic stripping voltammetry (SWCSV) was also taken into consideration. The selenium determined in the mineral waters here investigated is not over 600 ng L(-1); in three samples, it was found below the detection limit. Analysis of speciation revealed that Se(VI) is the highly prevailing form present: only two of the examined samples revealed a detectable amount (few ng L(-1)) of Se(IV). DPCSV made possible to detect, in two of the samples, the presence of a specie(s) able to interact with Se(IV). The apparent interaction constant for the adduct formation was evaluated and the species concentration determined. However, the nature of such compound(s) remains unknown. 相似文献
19.
The syntheses of five new aminoalkylbis(phenolate) ligands (as hydrochlorides) and their uranyl complexes are described. The reaction between uranyl nitrate hexahydrate and phenolic ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminopropane) · HCl], H2L1 · HCl, forms a uranyl complex [UO2(HL1)2] · 2CH3CN (1). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminobutane) · HCl], H2L2 · HCl, forms a uranyl complex with a formula [UO2(HL2)2] · 2CH3CN (2). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methyl benzyl)-1-aminohexane) · HCl], H2L3 · HCl, yields a uranyl complex with a formula [UO2(HL3)2] · 2CH3CN (3) and the ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-cyclohexylamine) · HCl], H2L4 · HCl, yields a uranyl complex with a formula [UO2(HL4)2] (4). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-benzylamine) · HCl], H2L5 · HCl, forms a uranyl complex with a formula [UO2(HL5)2] · 2MeOH (5). The molecular structures of 1, 2′ (2 without methanol), 3, 4 and 5 were verified by X-ray crystallography. The complexes 1–5 are neutral zwitterions which form in a molar ratio of 1:2 (U to L) in the presence of a base (triethylamine) and bear similar mononuclear, distorted octahedral uranyl structures with the four coordinating phenoxo ligands forming an equatorial plane and resulting in a centrosymmetric structure for the uranyl ion. In uranyl ion extraction studies from water to dichloromethane with ligands H2L1 · HCl–H2L5 · HCl, the ligands H2L2 · HCl and H2L4 · HCl are the most effective ones. 相似文献
20.
M. F. Barakat M. M. Abdel-Hamid 《Journal of Radioanalytical and Nuclear Chemistry》2001,247(1):159-163
The spectrophotometric determination of pure U(IV) or U(VI) ions in solution with Arsenazo I is greatly dependant on the pH of the solutions. The experimental conditions for the differential estimation of the different oxidation states of U ions, in the same sample, using Arsenazo I have been identified and implemented. The results showed that the applied method is rather rapid and accurate. 相似文献