Sorption of Aldrich Humic Acids onto Hematite: Insights into Fractionation Phenomena by Electrospray Ionization with Quadrupole Time-of-Flight Mass Spectrometry

International audienceSorption induced fractionation of purified Aldrich humic acid (PAHA) on hematite is studied through the modification of electrospray ionization (ESI)quadrupole time-of-flight (QToF) mass spectra of supernatants from retention experiments. The ESI mass spectra show an increase of the “mean molecular masses” of the molecules that constitutes humic aggregates. The low molecular weight fraction (LMWF; m/z ≤ 600 Da) is preferentially sorbed compared to two other fractions. The resolution provided by ESI-QToF mass spectrometer in the low-mass range provided evidence of further fractionation induced by sorption within the LMWF. Among the two latter fractions, the high molecular weight fraction (HMWF; m/z ≈ 1700 Da) seems to be more prone to sorption compared to the intermediate molecular weight fraction (IMWF; m/z ≈ 900 Da). The IMWF seems to be more hydrophilic as it should be richer in O, N and alkyl C from the proportion of even mass, and poorer in aromatic structures from mass defect analysis in ESI mass spectra

Quantitative description and local structures of trivalent metal ions Eu(III) and Cm(III) complexed with polyacrylic acid

The trivalent metal ion (M(III) = Cm, Eu)/polyacrylic acid (PAA) system was studied in the pH range between 3 and 5.5 for a molar PAA-to-metal ratio above 1. The interaction was studied for a wide range of PAA (0.05 mg L−1–50 g L−1) and metal ion concentrations (2×10−9–10−3 M). This work aimed at 3 goals (i) to determine the stoichiometry of M(III)–PAA complexes, (ii) to determine the number of complexed species and the local environment of the metal ion, and (iii) to quantify the reaction processes. Asymmetric flow-field-flow fractionation (AsFlFFF) coupled to ICP-MS evidenced that size distributions of Eu–PAA complexes and PAA were identical, suggesting that Eu bound to only one PAA chain. Time-resolved laser fluorescence spectroscopy (TRLFS) measurements performed with Eu and Cm showed a continuous shift of the spectra with increasing pH. The environment of complexed metal ions obviously changes with pH. Most probably, spectral variations arose from conformational changes within the M(III)–PAA complex due to pH variation. Complexation data describing the distribution of complexed and free metal ion were measured with Cm by TRLFS. They could be quantitatively described in the whole pH-range studied by considering the existence of only a single complexed species. This indicates that the slight changes in M(III) speciation with pH observed at the molecular level do not significantly affect the intrinsic binding constant. The interaction constant obtained from the modelling must be considered as a mean interaction constant

Review of Actinide Decorporation with Chelating Agents

International audienceIn case of accidental release of radionuclides in a nuclear facility or in the environment, internal contamination (inhalation, in-gestion or wound) with actinides represents a severe health risk to human beings. It is therefore important to provide effective che-lation therapy or decorporation to reduce acute radiation damage, chemical toxicity, and late radiation effects. Speciation governs bioavailability and toxicity of elements and it is a prerequisite tool for the design and success of new ligands or chelating agents. The purpose of this review is to present the state-of-the-art of actinide decorporation within biological media, to recall briefly actinide metabolism, to list the basic constraints of actinideeligand for development, to describe main tools developed and used for decorporation studies, to review mainly the chelating agents tested for actinides, and finally to conclude on the future trends in this field. To cite this article: E ´. Ansoborlo et al., C. R. Chimie X 33 (2007). Ó 2007 Académie des sciences. Published by Elsevier Masson SAS. All rights reserved.En cas de rejet accidentel de radionucléides dans une installation nucléaire ou dans l'environnement, il existe un risque de contamination interne (inhalation, ingestion ou blessure) pour l'homme et il est important de pouvoir fournir un traitement thérapeutique par des agents chélatants ou décorporation permettant de réduire la dose, la toxicité chimique et les effets retardés des radiations.La spéciation domine la biodisponibilité et la toxicité des éléments et représente un outil indispensable pour la conception et l'efficacité de nouveaux ligands ou chélatants. Le but de cet article est de présenter l'état de l'art sur la décorporation des actinides en milieu biologique, de rappeler les grandes lignes du métabolisme des actinides, de lister les contraintes indispensables actinide–ligands pour la décorporation, de décrire succinctement les principaux outils expérimentaux ou analytiques utilisés, de passer en revue les principaux ligands testés pour les actinides et de présenter les orientations du futur dans ce domaine

Study of thorium hydrolysis species by electrospray-ionization mass spectrometry

Electrospray-mass spectrometry (ES-MS) has been used for the first time to study the hydrolysis of thorium. Hence, important discrepancies exist in the literature concerning the appearance of the first hydroxo complex. By studying thorium species as a function of pH, it was possible to observe the appearance of the first thorium hydroxo complexes at pH I as well as the other hydroxo complexes at higher pH. By using MS/MS experiments, all thorium complexes corresponding to the different hydroxo thorium species, Th(OH)(3+), Th(OH)(2)(2+), Th(OH)(3)(+) were attributed. Speciation of Th-hydrolyzed complexes obtained by ES-MS is compared to that obtained in the literatur

Sulfate Complexation of Trivalent Lanthanides Probed by Nanoelectrospray Mass Spectrometry and Time-Resolved Laserinduced Fluorescence Spectroscopy

Conférence du 18 au 23 Septembre 2005. Communication par affiche

Dissociation of M(CO3)33- into M(CO3)2- for M3+ = Am3+ and Cm3+ at 10 to 70°C

Conférence du 18 au 23 Septembre 2005. Communication par affiche

Degradation kinetics of poly(ether-urethane) Estane((R)) induced by electron irradiation

Radiation effects on a segmented aromatic poly(ether-urethane) induced by electron beam irradiation under oxygen atmosphere were investigated using Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR) in order to determine the degradation mechanisms. Thin films have been irradiated under a dose rate of 1 MGy/h with absorbed doses varying from 25 to 1000 kGy under O-2. FTIR spectra have shown the formation of hydroperoxides, carboxylic acids, primary amines, alcohols, esters and formates. Moreover, the decrease of urethane and ether absorbances revealed the degradation of both soft and hard segments. Spin-trapping technique was used to monitor the evolution of short-lived peroxy and alkyl radicals at room temperature. Finally, a mechanism of degradation for electron irradiated polyurethane is propose

Sulfate Complexation of Trivalent Lanthanides Probed by Nanoelectrospray Mass Spectrometry and Time-Resolved Laser-Induced Luminescence

International audienceSulfate complexation of lanthanides is of great interest for predicting speciation of radionuclides in natural environments. The formation of LaSO4+(aq) in HNO3/H2SO4 aqueous solutions of low ionic strength (I) was studied by nanoelectrospray ionization mass spectrometry (nanoESI-MS). Several gaseous species containing LaSO4+ were detected. The formation constant of LaSO4+(aq) was determined and extrapolated to I = 0 (logβ°1 = 3.5 ± 0.3) by using a simple specific ion interaction theory (SIT) formula. This value supports the potential of nanoESI-MS for the study of kinetically labile species. The species La(SO4)2- was also detected. In addition, time-resolved laser-induced luminescence (TRLIL) was used to study Eu(III) speciation under ionic conditions of 0.02−0.05 M H+ (H2SO4/HClO4) and 0.4−2.0 M Na+ (Na2SO4/NaClO4). The data were interpreted with the species EuSO4+ (logβ°1 = 3.78 ± 0.1) and Eu(SO4)2- (logK°2= 1.5 ± 0.2). For extrapolating to I = 0, all of the major ions were taken into account through several SIT ion-pair parameters, ε. Most of the ε values were estimated by analogy to known parameters for similar ion-pair interactions using linear correlations, while εEu3+,SO42− = 0.86 ± 0.5 was fitted to the experimental data because, to date, SIT coefficients between multicharged species are not reported. The formation constants obtained here confirm some of those previously measured for Ln(III) and An(III) by various experimental techniques, and conversely do not give credit to the idea that in equilibrium conditions TRLIL and other spectroscopic techniques would provide stability constants of only inner-sphere complexes. The fluorescence lifetimes measured for EuSO4+ and Eu(SO4)2- were consistent with the replacement of one H2O molecule in the first coordination sphere of Eu3+ for each added SO42- ligand, suggesting a monodentate SO42- coordination

Stabilities of the Aqueous Complexes Cm(CO3)33_3)_3^3- and Am(CO3)33_3)_3^3- in the Temperature Range 10-70 \degres C

RADIOCHInternational audienceThe carbonate complexation of curium(III) in aqueous solutions with high ionic strength was investigated below solubility limits in the 10−70 °C temperature range using time-resolved laser-induced fluorescence spectroscopy (TRLFS). The equilibrium constant, K3, for the Cm(CO3)2- + CO32- ⇌ Cm(CO3)33- reaction was determined (log K3 = 2.01 ± 0.05 at 25°C, I = 3 M (NaClO4)) and compared to scattered previously published values. The log K3 value for Cm(III) was found to increase linearly with 1/T, reflecting a negligible temperature influence on the corresponding molar enthalpy change, ΔrH3 = 12.2 ± 4.4 kJ mol-1, and molar entropy change, ΔrS3 = 79 ± 16 J mol-1 K-1. These values were extrapolated to I = 0 with the SIT formula (ΔrH3° = 9.4 ± 4.8 kJ mol-1, ΔrS3° = 48 ± 23 J mol-1 K-1, log K3° = 0.88 ± 0.05 at 25°C). Virtually the same values were obtained from the solubility data for the analogous Am(III) complexes, which were reinterpreted considering the transformation of the solubility-controlling solid. The reaction studied was found to be driven by the entropy. This was interpreted as a result of hydration changes. As expected, excess energy changes of the reaction showed that the ionic strength had a greater influence on ΔrS3 than it did on ΔrH3

Analysis of the metal-binding selectivity of the metallochaperone CopZ from Enterococcus hirae by electrospray ionization mass spectrometry

International audienc