Spéciation du Silicium dans les charges d'hydrotraitement

Le silicium est connu pour être un poison sévère des catalyseurs d'hydrotraitement (HDT). L objectif de la thèse a donc été de mettre en place des outils analytiques pour la spéciation du silicium afin d'identifier toutes les molécules silicées réellement formées dans les charges d'HDT. Différents outils analytiques de pointe basés sur des couplages entre la chromatographie en phase gazeuse et la spectrométrie de masse (MS et ICP/MS) ont été développés. Étant donnée la réactivité de certaines espèces silicées, des échantillons représentatifs de la dégradation du PDMS ont été produits dans des conditions de craquage thermique d'un mélange heptane/xylène. L'application à ces échantillons de la stratégie analytique, développée initialement, a démontré la présence du silicium sous différentes formes chimiques. Plus d une centaine de molécules réparties en 10 familles comprenant un nombre d atomes de silicium entre 1 et 1500 a été caractérisée. Ces composés silicés vont donc pouvoir être présents dans toutes les coupes pétrolières, des fractions gaz aux fractions les plus lourdes, couvrant ainsi un domaine de coupes pétrolières beaucoup plus vaste que celui des essences. Les siloxanes cycliques (Dn) ont été confirmés comme produits majoritaires de dégradation du PDMS. Les autres composés silicés, jamais caractérisés pour la plupart, sont présents à l état de traces mais possèdent des groupements réactifs de type hydroxy, métoxy, hydropéroxy susceptibles d interagir fortement avec le support du catalyseur (Al2O3) et donc de conduire à sa désactivation.Silicon is known to be a severe poison for hydrotreatment (HDT) catalysts especially in naphtha and gasoline samples. The objective of the PhD was to develop analytical methods for silicon speciation in order to characterize silicon molecules formed during refining steps which potentially affects HDT catalysts. For the analytical strategy, different high-technology analytical tools based on gas chromatography coupled to mass spectrometry (MS and ICP/MS) were developed. Due to the high reactivities of several silicon species, representative samples of PDMS degradation were produced under thermal cracking of a mixture of heptane/xylene (500C) using a pilot plant. The previously developed analytical strategy was applied to these samples and demonstrated the occurrence of silicon under a wide array of chemical forms. More than a hundred of silicon species belonging to 10 chemical families with a number of silicon atoms ranging from 1 to 1,500 were characterized. These silicon compounds could be present in all petroleum cuts, from the gas fractions to the heavier fractions. Therefore, the investigated range of boiling points was inevitably more important than for naptha and gasoline cuts. Cyclic siloxanes (Dn) were confirmed as the major PDMS degradation products. The other silicon compounds, almost never characterized before, were recovered at trace levels but consisted of reactive groups such as hydroxy, methoxy and hydroperoxy. These silicon species were able to strongly react with the catalytic support (Al2O3) and led to its deactivationPAU-BU Sciences (644452103) / SudocSudocFranceF

Characterization of the aerosol produced by infrared femtosecond laser ablation of polyacrylamide gels for the sensitive inductively coupled plasma mass spectrometry detection of selenoproteins

A 2D high repetition rate femtosecondlaserablation strategy (2-mm wide lane) previously developed for the detection of selenoproteins in gel electrophoresis by inductively coupled plasma mass spectrometry was found to increase signal sensitivity by a factor of 40 compared to conventional nanosecond ablation (0.12-mm wide lane) [G. Ballihaut, F. Claverie, C. Pécheyran, S. Mounicou, R. Grimaud and R. Lobinski, Sensitive Detection of Selenoproteins in Gel Electrophoresis by High Repetition Rate FemtosecondLaserAblation-Inductively Coupled Plasma Mass Spectrometry, Anal. Chem. 79 (2007) 6874–6880]. Such improvement couldn't be explained solely by the difference of amount of material ablated, and then, was attributed to the aerosol properties. In order to validate this hypothesis, the characterization of the aerosolproduced by nanosecond and high repetition rate femtosecondlaserablation of polyacrylamidegels was investigated. Our 2D high repetition rate femtosecondlaserablation strategy of 2-mm wide lane was found to produce aerosols of similar particle size distribution compared to nanosecond laserablation of 0.12-mm wide lane, with 38% mass of particles < 1 µm. However, at high repetition rate, when the ablated surface was reduced, the particle size distribution was shifted toward thinner particle diameter (up to 77% for a 0.12-mm wide lane at 285 µm depth). Meanwhile, scanning electron microscopy was employed to visualize the morphology of the aerosol. In the case of larger ablation, the fine particles ejected from the sample were found to form agglomerates due to higher ablation rate and then higher collision probability. Additionally, investigations of the plasma temperature changes during the ablation demonstrated that the introduction of such amount of polyacrylamidegel particles had very limited impact on the ICP source (ΔT~ 25 ± 5 K). This suggests that the cohesion forces between the thin particles composing these large aggregates were weak enough to have negligible impact on the ICPMS detection

Evaluation de la contamination atmosphérique des écosystèmes en utilisant la composition isotopique du plomb et du mercure dans les lichens

La signature isotopique du plomb (Pb) et du mercure (Hg) a été étudiée dans les lichens épiphytes des Pyrénées-Atlantiques. Un échantillonnage intégré et spatialisé à l aide d un système d information géographique (SIG) a été mis en place afin de prendre en compte la diversité du territoire (occupation des sols, forêts, agriculture, industries et zones urbaines). A méso-échelle (département des Pyrénées-Atlantiques), la composition isotopique permet de différencier les zones impactées par les activités anthropiques mais aussi de discriminer l origine de la contamination qu elle soit de type industrielle ou urbaine. A l échelle locale, la signature isotopique du Hg et Pb dans des lichens et des mousses prélevés dans la forêt d Iraty (zone frontalière Franco-espagnole) a permis d évaluer le type de dépôts accumulés dans ces différents bioaccumulateurs atmosphériques et le potentiel de ce nouvel outil pour le suivi des dépôts atmosphériques dans les écosystèmes éloignés. Enfin, sur la zone mercurifère d Almadén (Castella la Mancha, Espagne) la signature isotopique du Hg dans les lichens et les sédiments apparait comme un outil pertinent pour étudier le transfert du Hg provenant de l extraction minière vers les hydrosystèmes et l atmosphère.The isotopic signature of lead (Pb) and mercury (Hg) was measured in epiphytic lichens from Pyrénées-Atlantiques. An integrated and spatialized sampling was developed using geographical information system (GIS) to take into account the diversity of the territory (land-use, forest, agriculture, industries and urban areas). At meso-scale (county, Pyrenees-Atlantiques) the isotopic composition allows to differenciate areas impacted by anthropegenic activities and discriminate the origin of the contamination that it of industrial or urban type. At local scale, the isotopic signature of Hg and Pb in lichens and mosses sampled in Iraty forest (Franco-Spanish border) allowed to evaluate the kind of atmospheric deposits in these atmospheric bio-monitors and the potential of this new tool for the monitoring of atmospheric depositsin remote ecosystems. Finally, on the mercurifere area of Almadén (Castella la Mancha, Spain) the isotopic fingerprint of Hg in lichens and sediments appears to be a relevant tool to study the transfer of Hg from mining activities to hydrosystems and atmosphere.PAU-BU Sciences (644452103) / SudocSudocFranceF

Développement de la microchimie élémentaire et isotopique (87Sr (86Sr) des otolithes de saumons Atlantique)

Le saumon Atlantique fait partie du patrimoine écologique et économique du bassin de l Adour. Dans le cadre de la gestion actuelle du saumon dans ce bassin, l origine natale des géniteurs, le taux de retour des individus d origine piscicole, le taux de homing sur chaque sous-bassin ou encore le soutient par des géniteurs extérieurs au bassin de l Adour sont des thématiques qui restent sans réponses. Ce projet propose donc de tester le potentiel de la géochimie des otolithes sur le saumon Atlantique du bassin de l Adour. Nos travaux démontrent que la variation géographique de la composition chimique de l eau dans 12 rivières colonisées par le saumon, associée à un enregistrement dans l otolithe proportionnel à la signature géochimique du milieu de vie, permettent de discriminer l origine géographique des individus. La combinaison des signatures élémentaires (Sr:Ca et Ba:Ca) et surtout l isotopie du Sr (temporellement plus stable et sans fractionnement biologique) dans les otolithes améliore la précision du classement à l échelle de la rivière de développement. En se basant sur la transmission de signatures géochimiques (élémentaires et isotopiques) transgénérationelles entre la femelle reproductrice et les otolithes des embryons produits par cette dernière, nous avons discriminé avec succès les individus nés en rivière de ceux nés en pisciculture. Le classement des géniteurs (180 individus) selon leur rivière natale a confirmé que le sous bassin du gave d Oloron, et plus particulièrement le gave d Ossau, reste le lieu qui produit le plus de saumon de retour. De façon non négligeable, le gave de Pau contribue lui aussi au renouvellement de la population (10 d origine piscicole et 6 d origine naturelle). 18 saumons sur 180 sont issus de l alevinage (soit 10%); la majorité s étant développée dans le sous-bassin du gave de Pau. Par ailleurs, nous avons mis à jour l existence de périodes au cours de la vie des juvéniles (changements de milieu: sac vitellin milieu extérieur et pisciculture rivière) durant lesquelles l enregistrement du Ba dans l otolithe n est pas en relation avec la chimie de l eau. L originalité de notre approche est d avoir étudié l influence des facteurs endogènes et environnementaux chez des poissons ayant vécu dans le milieu naturel ou ayant séjourné en milieu naturel contrôlé. Nos travaux mettent l accent sur la complexité de l intégration du rapport Ba:Ca dans l otolithe et démontrent l utilité des éléments traces et des isotopes du Sr comme tag naturel pour distinguer l origine natale du saumon Atlantique.The Adour basin holds one of the largest populations of Atlantic salmon in southern Europe exploited by commercial and sport fisheries. Determining the relative contributions of individual rivers and hatcheries to the Adour basin populations becomes crucial to understand key sources that contribute the most to its persistence. We successfully used Sr:Ca, Ba:Ca and 87Sr:86Sr ratios as natural tags for determining the natal origins of adults from 12 tributaries. Success in discriminating between fish from different sites was greatest using Sr isotopes since the latter remained relatively constant across years at a given location. Geochemical signatures from core regions of the otolith were also used to identify fish from hatchery or naturally spawned sources. The predominance of adults spawned in the Ossau River among returning adults corresponded with long-term juvenile production trends in the Ossau River. Despite the limited upstream accessibility of the Pau River, our study demonstrated that Atlantic salmon recruits can successfully leave this river to join the adult population in the Adour basin. We observed relatively clear separation between hatchery and wild juveniles using both Sr:Cacore (wild > 2.5 and hatchery 0.710). The return of hatchery reared fish as adult spawners represented 10% of the total sampled fish we analyzed. Almost all adults, previously identified as belonging to the Ouzom River, were hatchery produced. Adults originated from the Pau River were either wild or hatchery reared fish. We also conducted field controlled experiments that characterized the elemental uptake process in juvenile Atlantic salmon otoliths during freshwater residency. Physiological effects influenced Ba deposition. Ba:Ca otolith profiles from hatchery-reared and field collected fish were characterised by a peak at yolk absorption mark. Hatchery-reared fish stocked in a river also displayed a peak of Ba:Ca following transfer which was not related to the water chemistry. Our experiment revealed a 20-day lag time between initial Ba:Cawater changes and Ba:Caotolith saturation. Results suggested that such effects should be considered during any attempts to determine rivers of origin of Atlantic salmon based on otolith elemental composition or reconstruct the movement of individual fish among and within streams.PAU-BU Sciences (644452103) / SudocSudocFranceF

Elemental fractionation effects in high repetition rate IR femtosecond laser ablation ICP-MS analysis of glasses

An IR-femtosecond laser ablation ICPMS coupling was used to investigate the influence of the high repetition rate on elemental fractionation effects for the analysis of silicate glass SRM NIST 610. First, elemental fractionation inherent to the ICP was minimised by working on wet plasma conditions which had greater tolerance to mass loading and demonstrated a higher robustness compared to dry plasma conditions. Because of the use of a narrow laser beam producing small craters (17 µm in diameter), a special arrangement of pulses was used to perform resulting craters of 100 µm diameter. The ablation strategy developed in this work consisted in a series of concentric circle trajectories ablated at high repetition rates by moving the laser beam rapidly thanks to a scanning beam device. Two scanner speeds (0.25 mm s−1 and 1.5 mm s−1), five laser repetition rates (from 0.1 kHz to 10 kHz) and three fluence values (5 J cm−2, 14 J cm−2, and 25 J cm−2) were investigated in detail. For this purpose, critical elemental ratios (namely 238U/232Th, 208Pb/238U, and 66Zn/65Cu) of aerosols produced by fs-LA of silicate glass were studied to evaluate the impact of the different laser parameters on elemental fractionation . No heating zones or preferential evaporation of elements were found depending on the repetition rate employed. However, particle-size-fractionation was measured during the ablation of the sample surface, and this effect was reduced by using a high repetition rate as well as a high scanner speed which allow the dilution of the large particles coming from the surface layer with finer particles coming to deeper levels. Additionally, the ablation rate induced by the selected ablation strategy had a low influence on fractionation effects due to the high robustness of the ICP plasma and, on the other hand, fractionation indices were not particularly affected by the laser repetition rate although they could be improved by the use of high fluence values. Finally, it could be stressed that no differences on the structure of the aerosol particles collected on membrane filters were found depending on the ablation parameters

Recent developments and trends in the application of strontium and its isotopes in biological related fields

Strontium is a chemical element without biological functions in humans. In fact, only two biological roles are known, both as a biomineral constituent. However, strontium and calcium (a significant biometal) present chemical similarities; hence, the absorption of the former by living organisms is plausible. Based on the particular properties of isotopes of strontium several applications of this chemical element in biological sciences have been developed. These include its radioactive and non-radioactive isotopes in medical applications or resorting to its stable isotopes as analytical tools in isotope fingerprinting (87Sr/86Sr) to study dietary habits and migration patterns of ancient populations, food authentication and forensic sciences. This article, reviews papers published between 2012 and 2016, highlights the use of strontium isotope ratios for such biological related applications and compiles an analytical database, providing a valuable tool for future studies in the area.This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement Nº 739568. JALS is indebted to Fundação para a Ciência e a Tecnologia (FCT), Portugal, for financial support (project UID/QUI/00100/2013).info:eu-repo/semantics/publishedVersio

Trace Elements Analysis of Tunisian and European Extra Virgin Olive Oils by ICP-MS and Chemometrics for Geographical Discrimination

The aim of this study was to investigate the levels of trace elements in olive oils from different locations and their use for geographical authentication. Concentrations of seventeen elements were determined in a total of 42 olive oils from Tunisia, Spain (Basque country), and southern France, and in nine soil samples from Tunisia by quadrupole inductively plasma mass spectrometry. The compilation of appropriate techniques integrated into the analytical procedure achieved a precision (RSD) between 2% and 15% and low limits of detection (between 0.0002 and 0.313 µg kg−1). The accuracy of the analytical method applied for olive oil analysis was evaluated using SRM NIST 2387 Peanut butter. The recoveries obtained after microwave-assisted digestion for the certified elements ranged between 86% and 102%. Concentrations of non-certified elements (V, Cr, Co, Ni, Ba, Rb, Sr, Cd, Pb, and As) were presented. The use of Pearson correlation applied on paired Tunisian oil/soil samples has shown that several elements (Mg, Mn, Ni, and Sr) were significantly correlated. The multivariate statistics using principal component analysis have successfully discriminated against three studied origins. The most significant variables were the elemental concentrations of Cu, Cr, Fe, Mn, Sr, V, and Zn. This study shows the potential of applying trace elements profiles for olive oil geographical discrimination.This research was funded by European Project TunTwin from the Horizon 2020 Framework program of the European Union under grant No. 952306. It was also funded by the French ANR EquiPex MARSS project with a contribution of the METROFOOD ESFRI project. This work was partially supported by the Euskadi/Nouvelle Aquitaine/Navarra Eurorregion through the research project ISOTOPO (with agreement no. 2020/3). The financial support of a Ph.D. grant for Emna G. Nasr has been provided by the “Excellence Eiffel” scholarship of Campus France, the European project “TunTwin” and the scholarship “bourse d’alternance” of University Tunis El Manar, Ministry of Higher Education and Scientific Research in Tunisia

Determination of 87Sr/86Sr isotopic ratio in olive oil and pomace using multicollector-ICPMS; analysis of pomace residues as a simpler approach for determination of 87Sr/86Sr ratio in olive oil with low Sr content

This study presents an analytical procedure for measuring the 87Sr/86Sr isotopic ratio in olive oil and pomace using multicollector-inductively coupled mass spectrometry (MC-ICPMS). The developed method combines liquid-liquid extraction with an acid solution and degradation of organic residues in the extract by dry ashing and oxidation by H2O2 and HNO3. The method enabled 87Sr/86Sr ratios to be obtained in olive oil with Sr content as low as 0.2 ng/g, with a precision of 54 ppm. The method’s validity was confirmed by an interlaboratory comparison using NIST SRM 2387, providing the first data on its elemental Sr (2380 ± 230 ng/g ; n = 10), and 87Sr/86Sr isotopic composition (0.70908 ± 0.00004 ; n = 14). The procedure was applied to olive oil and pomace samples, showing that they have an identical 87Sr/86Sr ratio, which was consistent with that determined in soils from the same orchards. The results thus revealed that Sr isotopic ratios of olive oil and pomace can both be used in geographical traceability studies of olive oil, which means that, instead of processing large volume of oil, characteristic 87Sr/86Sr signatures of olive oil can be more easily obtained by analyzing small quantities of pomace obtained by centrifuging the oil

Equilibrium studies of ternary complexes formed by bromide, sulfate, selenite and selenate ions with Zn2+, Mg2+ and 1, 4, 7, 13, 16, 19-hexaaza- 10, 22- dioxacyclotetracosane (obisdien)

Bromide, sulfate, selenite and selenate were found to form bridges in the cavity of mononuclear and binuclear Obisdien:Zn(II) and Obisdien:Mg(II) complexes in aqueous solution at 25.0 °C and m = 0.100 M (KCl). Potentiometric equilibrium measurements were used to determine the formation constants of the species formed in these systems in the pH range 2-12. For the Obisdien: Zn2+:anions complexes, we have established the existence of four species for bromide ion, five species for sulfate ion, six species for selenite ion and four species for selenate ion. We found that the hydroxo binuclear complexes predominate over the others species, and the binding strength decreases in the sequence: SeO4(2-) > SeO3(2-) > SO4(2-) > Br-. The Obisdien:Mg(II) system presents three species in case of binding with bromide ion, four with sulfate ion, five with selenite ion and five with selenate ion. Variation of the binding strength in the Obisdien:Mg(II) complexes is the same as in the Obisdien:Zn(II) complexes: SeO4(2-) > SeO3(2-) > SO4(2-) > Br-. Molecular mechanics calculations show that the dizinc(II)- and dimagnesium(II)-Obisdien complexes adopt several low energy conformations differing in their Zn to Zn and Mg to Mg separations that allow the coordination of SeO4(2-), SeO3(2-), SO4(2-), Br- and OH- anions

The stability of major and trace element concentrations from musts to Champagne during the production process

Thirty-nine Champagnes from six different brands originating from the AOC Champagne area were analyzed for major and trace element concentrations in the context of their production processes and in relation to their geographical origins. Inorganic analyses were performed on the must (i.e., grape juice) originating from different AOC areas and the final Champagne. The observed elemental concentrations displayed a very narrow range of variability. Typical concentrations observed in Champagne are expressed in mg/L for elements such as K, Ca, Mg, Na, B, Fe, A, and Mn. They are expressed in µg/L for trace elements such as Sr, Rb, Ba, Cu, Ni, Pb Cr and Li in decreasing order of concentrations. This overall homogeneity was observed for Sr and Rb in particular, which showed a very narrow range of concentrations (150 &lt; Rb &lt; 300 µg/L and 150 &lt; Sr &lt; 350 µg/L) in Champagne. The musts contained similar levels of concentration but showed slightly higher variability since they are directly influenced by the bedrock, which is quite homogenous in the AOC area being studied. Besides the homogeneity of the bedrock, the overall stability of the concentrations recorded in the samples can also be directly linked to the successive blending steps, both at the must level and prior to the final bottling. A detailed analysis of the main additives, sugar, yeast and bentonite, during the Champagne production process, did not show a major impact on the elemental signature of Champagne