22541-18-0Relevant academic research and scientific papers
Europium(III) complexed by HPSEC size-fractions of a vertisol humic acid: Small differences evidenced by time-resolved luminescence spectroscopy
Reiller, Pascal E.,Brevet, Julien,Nebbioso, Antonio,Piccolo, Alessandro
, p. 1173 - 1179 (2011)
The size fractionation of a humic acid (HA) by high performance size exclusion chromatography (HPSEC) was used as a proxy for the filtration effect during HA transport through a porous medium with minimum specific chemical interactions. The modification of the Eu(III)-HA complexes' formation with the different size-fractions, as compared to the bulk HA, was studied in time-resolved luminescence spectroscopy (TRLS). Clear modifications in Eu(III)-HA complexes' structures were shown and related to the molecular characteristics of the separated size-fractions. The properties of most of size-fractions did not induce a major alteration of the affinity towards Eu(III). Only the most hydrophilic fractions eluted in the tail of the chromatographic peak, representing about 11% of total fractions-weight, gave some significantly different parameters. Using a simplistic complexation model, it was found that the available complexation sites decreased with the size reduction of humic fractions.
Electron transfer. 44. Decreases in the effectiveness of redox catalysts with use
Radlowski,Chum,Hua, Louise,Heh, Jack,Gould
, p. 401 - 407 (1980)
Pyridine derivatives, which, when uncoordinated, catalyze outer-sphere electron-transfer reactions between metal centers, often undergo loss of catalytic activity with use. The active intermediates in such catalyzed reactions are radicals (cat?) formed by initial reaction of the catalysts with the primary reducing centers. This study examines the deterioration of a number of such catalysts in reactions of Eu2+ and V2+ with (NH3)5Co(py)3+. This deterioration, when it occurs, arises from interaction of the catalyst and the reducing center; it does not require Co(III). Degrees of deterioration vary widely. The very powerful catalysts derived from 2,4-pyridinedicarboxylic acid (III) lose much or all of their catalytic activity during the course of a single 1-min run with Eu2+ in excess, whereas catalytic erosion of isonicotinic acid (I), its esters, and its nitrile is negligible after treatment with excess reductant for 10-20 min. Erosion is much more marked with Eu2+ than with the less strongly reducing V2+ and is much less severe when the oxidant, rather than the reductant, is taken in excess. Deterioration in Eu2+ systems may be decreased strikingly by addition of excess Eu3+ and that in V2+ systems by addition of V3+. The spectra of the products formed when the more fragile catalysts react rapidly with Eu2+ (in the absence of Co(III)) correspond to those formed by reduction of the catalysts with zinc amalgam, which is presumed to be a two-electron reductant. The more robust isonicotinate catalysts are not affected by Eu2+ under similar conditions. Evidence is presented in support of two attrition mechanisms. The catalytic deterioration of 2,4-pyridinedicarboxylic acid in Eu2+ systems appears to involve disproportionation of catalyst-radical pairs (2cat? + 2H+ → cat + catH2), converting one member of each pair to an inactive dihydro species and returning the other to the catalyst pool. Measurements of the rate of deterioration of this catalyst allow us to estimate the specific rate for the disproportionation as 5.8 × 108 M-1 s-1. In systems featuring less fragile catalysts (e.g., isonicotinamide) the steady-state concentration of the radical, cat?, is so low that attrition, if it takes place at all, occurs mainly by reductive deterioration (cat? + Eu2+ →2H+ Eu3+ + catH2). In two such instances, comparison of kinetic runs using catalyst preparations that have undergone partial attrition permits an estimate of the specific rates of such deteriorative processes. Although both modes of attrition are presumed to occur in each catalytic system, bimolecular disproportionation appears to compete most favorably with reductive deterioration when the extent of reduction of the catalyst to its radical is greatest.
Energy transfer in the chemiluminescent system: Eu(II)/(III)-N3--H2O2
Elbanowski,Staninski,Kaczmarek,Lis
, p. 670 - 672 (2001)
Chemiluminescence (CL) in the systems containing Eu(II), Eu(III) ions and hydrogen peroxide has been investigated. Earlier results show that these systems are sources of excited Eu(III) ions and singlet oxygen generated in the recombination reactions of the hydroxyl radicals which originate from hydrogen peroxide decomposition. The excited Eu(III) ions undergo radiative deactivation. The addition of azide ions (N3-) to the Eu(II)/(III)-H2O2 system causes a significant increase in the chemiluminescence intensity and yield as a result of the energy transfer process from the dimers of singlet oxygen to Eu(III) ions. Taking into account the kinetic and spectral data obtained from the systems studied, the scheme of processes is proposed, and the quantum yield of chemiluminescence is estimated using the CL standard system: luminol-haemin-H2O2.
Kinetics and mechanism of the reaction of aqueous europium(II) ion with pyruvic acid
Konstantatos,Vrachnou-Astra,Katsaros,Katakis
, p. 122 - 126 (1982)
EuII ion reacts with pyruvic acid in air-free, aqueous, acidic solutions. The only organic product is lactic acid, which forms after a two-electron reduction of the keto form of pyruvic acid. The overall stoichiometry is 2:1, metal ion to organic acid, respectively. The kinetics were studied in detail by the stopped-flow technique. Under conditions of excess EuII ion over pyruvic acid, two stages are observed: a fast stage, which corresponds to the reduction of all available keto form in equilibrium with the hydro form of pyruvic acid, and a slow stage, during which hydrated pyruvic acid reacts only after being transformed to the carbonyl form by an acid-catalyzed reaction, which under these conditions is the rate-determining step. A mechanism is proposed and compared to the mechanisms of the corresponding reactions of the d elements Cr2+, V2+, and Ti3+.
Resonance light scattering properties of Eu3+ in gold colloid
Jian, Zhu,Xiang, Zhu
, (2005)
Gold colloidal containing rare-earth ions Eu3+ were prepared at room temperature. Fluorescence spectra and resonance light scattering (RLS) spectra of Eu3+ ions and gold colloid containing Eu3+ were measured. For solution
Study on the interaction between nucleic acid and Eu3+-oxolinic acid and the determination of nucleic acid using the resonance light scattering technique
Wu, Xia,Sun, Shuna,Yang, Jinghe,Wang, Minqin,Liu, Liyan,Guo, Changying
, p. 896 - 901 (2005)
At pH 9.75, the resonance light scattering (RLS) intensity of OA-Eu 3+ system is greatly enhanced by nucleic acid. Based on this phenomenon, a new quantitative method for nucleic acid in aqueous solution has been developed. Under the optimum condition, the enhanced RLS is proportional to the concentration of nucleic acid in the range of 1.0 × 10-9 to 1.0 × 10-6 g/ml for herring sperm DNA, 8.0 × 10 -10 to 1.0 × 10-6 g/ml for calf thymus DNA and 1.0 × 10-9 to 1.0 × 10-6 g/ml for yeast RNA, and their detection limits are 0.020, 0.011 and 0.010 ng/ml, respectively. Synthetic samples and actual samples were satisfactorily determined. In addition, the interaction mechanism between nucleic acid and OA-Eu3+ is also investigated.
Dissociation kinetics of macrocyclic trivalent lanthanide complexes of 1-oxa-4,7,10-triazacyclododecane-4,10-diacetic acid (H2ODO2A)
Allen Chang,Lin, Chih-Cheng,Kuo, Chien-Hung
, p. 2204 - 2216 (2015/02/02)
The dissociation rates of LnODO2A+ complexes (ODO2A2- is the deprotonated dianion of the ligand H2ODO2A, 1-oxa-4,7,10-triazacyclododecane-4,10-diacetic acid) are all faster than those of the corresponding LnDO2A+/sup
Dissociation kinetics of macrocyclic trivalent lanthanide complexes of 1,4,7,10-tetraazacyclododecane-1,7-diacetic acid (DO2A)
Lin, Chih-Cheng,Chen, Chia-Ling,Liu, Kuan-Yu,Chang, C. Allen
, p. 6268 - 6277 (2011/07/09)
The [H+]-catalyzed dissociation rate constants of several trivalent lanthanide (Ln) complexes of 1,4,7,10-tetraazacyclododecane-1,7- diacetic acid (LnDO2A+, Ln = La, Pr, Eu, Er and Lu) have been determined in two pH ranges: 3.73-5.11
Liquid-liquid solvent extraction of rare earths from chloride medium with sec-nonylphenoxy acetic acid and its mixtures with neutral organophosphorus extractants
Xiao, Pengfei,Bao, Changli,Song, Naizhong,Li, Cui,Jia, Qiong
, p. 1157 - 1161 (2011/10/18)
In the present study, sec-nonylphenoxy acetic acid (CA100) and its mixtures with four neutral organophosphorus extractants, tri-butyl-phosphate (TBP), 2-ethylhexyl phosphonic acid di-2-ethyl ester (DEHEHP), Cyanex923, and Cyanex925 have been applied to the extraction of rare earths. Results show that all the four mixing systems do not have evident synergistic effects on the extraction of rare earths. The different extraction effects have been considered to the separation of rare earths. The four mixtures may be applied to the separation of yttrium from some certain lanthanoids at proper mole fractions of CA100. Pleiades Publishing, Ltd., 2011.
Determination of Eu(III) based on fluorescence and cofluorescence enhancement of Eu(III)-Tb(III)tetracycline-eitrate system
Wang, Xiaoli,Zhao, Huichun,Jin, Linpei
, p. 1801 - 1804 (2008/03/17)
A new sensitized cofluorescence system has been developed for the determination of Eu(III) based on its complex formation with tetracycline (TC) in the presence of citrate and Tb(III). Eu(III) forms complex with tetracycline in alkaline condition which emits intrinsic fluorescence of Eu(III) when excited. The fluorescence intensity of Eu(III)-TC is enhanced about 5 times when citrate and Tb(III) are introduced. The factors that influence the fluorescence intensity of the system have been studied in detail. Under optimum conditions, the relative fluorescence intensity is linear in over the range 6.0×10-9 to 4.0×10-6 M of Eu(III). The detection limit has been found to be 1.4×10-9 M of Eu(III). The method has been used for the determination of Eu in two rare earth samples with relative error 4.5% and -1.8%, and RSD 2.6% and 2.1%, respectively.
