Cu fractionation, isotopic analysis, and data processing <i>via</i> machine learning: new approaches for the diagnosis and follow up of Wilson's disease <i>via</i> ICP-MS

Information about Cu fractionation and Cu isotopic composition can be paramount when investigating Wilson's disease (WD). This information can provide a better understanding of the metabolism of Cu. Most importantly, it may provide an easy way to diagnose and to follow the evolution of WD patients. For such purposes, protocols for Cu determination and Cu isotopic analysis via inductively coupled plasma mass spectrometry were investigated in this work, both in bulk serum and in the exchangeable copper (CuEXC) fractions. The CuEXC protocol provided satisfactory recovery values. Also, no significant mass fractionation during the whole analytical procedure (CuEXC production and/or Cu isolation) was detected. Analyses were carried out in controls (healthy persons), newborns, patients with hepatic disorders, and WD patients. While the results for Cu isotopic analysis are relevant (e.g., δ65Cu values were lower for both WD patients under chelating treatment and patients with hepatic problems in comparison with those values obtained for WD patients under Zn treatments, controls, and newborns) to comprehend Cu metabolism and to follow up the disease, the parameter that can help to better discern between WD patients and the rest of the patients tested (non-WD) was found to be the REC (relative exchangeable Cu). In this study, all the WD patients showed a REC higher than 17%, while the rest showed lower values. However, since establishing a universal threshold is complicated, machine learning was investigated to produce a model that can differentiate between WD and non-WD samples with excellent results (100% accuracy, albeit for a limited sample set). Most importantly, unlike other ML approaches, our model can also provide an uncertainty metric to indicate the reliability of the prediction, overall opening new ways to diagnose WD

Sr Isotopic Composition of NIES Certified Reference Material No. 28 Urban Aerosols

An interlaboratory study of the National Institute for Environmental Studies (NIES) certified reference material (CRM) No. 28 Urban Aerosols collected from the filters of a central ventilating system in a building in the Beijing city center from 1996 to 2005 was performed to obtain an information value of the Sr isotopic composition. The Sr isotopic composition was measured using multi-collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) to confirm the CRM’s within- and between-bottle homogeneity, and the results showed a 87Sr/86Sr ratio of 0.710227 ± 0.000019 (2SD, n = 18). The Sr isotopic compositions were intercompared using thermal ionization mass spectrometry (TIMS), which showed good agreement with values obtained at NIES. Subsequently, a consistent 87Sr/86Sr ratio was observed between two dissolution (hotplate vs. high-pressure bomb) and Sr separation (Sr spec resin vs. cation exchange resin) methods. To validate and reproduce the accuracy of our analytical methods, the Sr isotopic compositions of secondary reference materials, JB-1b and JA-2, were also measured. Our results showed that NIES CRM No. 28 is appropriate for the quality control of Sr isotope measurements of particulate matter analyses for environmental and geochemical studies

New sample introduction strategies in MC-ICP-MS for the isotopic bio-geochemistry of mercury at ultra-trace level

En complément des analyses de concentration et de spéciation, les analyses des isotopes stables du mercure par MC-ICP-MS sont à l’heure actuelle un outil majeur pour tracer les sources et les transformations de cet élément dans l’environnement. Cette thèse propose le développement de techniques de pré-concentrations couplées au MC-ICP-MS afin de réaliser des analyses isotopiques de mercure au niveau du ng.L-1 (Ultra-trace). La stratégie de pré-concentration en ligne va générer des signaux transitoires courts dont la gestion en MC-ICP-MS représente un réel défi. Afin d’y répondre, une méthode de traitement de données adaptée à ce type de signaux ainsi qu’une méthode de correction du phénomène de dérive isotopique ont été développées. Dans le but de déterminer des compositions isotopiques en mercure total à de faibles concentrations, le couplage d’une génération de vapeur froide, d’une double amalgamation sur or (CVG-DGA) et d’un MC-ICP-MS a été développé. Cette nouvelle technique donne des précisions externes de l’ordre de 0.20 à 0.30‰ (2SD) pour des concentrations en mercure de 5 ng.L-1 en solution. Cette thèse présente également une nouvelle méthode d’analyse isotopique par espèce chimique (CSIA) réalisée à l’aide du couplage d’une chromatographie en phase gazeuse équipée d’un injecteur PTV (GC-PTV) et d’un MC-ICP-MS. Celle-ci permet l’analyse isotopique de plusieurs espèces chimiques avec des précisions externes de l’ordre de 0.30 à 0.40‰ (2SD) pour des concentrations en mercure de 150 ng.L-1 dans des échantillons biologiques.Les développements analytiques de cette thèse ont permis de mesurer directement et de façon automatisée des compositions isotopiques de mercure à des niveaux d’ultra-trace (jusqu’à 5ng.L-1) tout en conservant des précisions compatibles avec les principales questions environnementales posées. Ceci va permettre d’analyser des compartiments environnementaux contenant de faibles quantités de mercure (eaux naturelles, planctons,…) et ouvre ainsi de nouvelles perspectives pour une meilleure compréhension du cycle bio-géochimique du mercure.In addition to the quantitative and speciation analysis, the analysis of mercury stable isotopes by MC-ICP-MS are now a tool of choice to track sources and pathways of this element in the environment. This PhD thesis presents the development of hyphenation between pre-concentration techniques and MC-ICP-MS to measure isotopic composition of mercury at ng.L-1 levels (Ultra-trace). The on-line pre-concentration strategy will create short transient signals which represent a real challenge for MC-ICP-MS. In order to solve it, a data treatment strategy for this particular signals and a correction method for the isotopic drift were developed.The hyphenation between a cold vapor generation, a dual gold amalgamation (CVG-DGA) and a MC-ICP-MS was developed to determine total mercury isotopic composition. This new technique gives external precisions ranging from 0.20 to 0.30‰ (2SD) for Hg concentration in solution of 5 ng.L-1. This PhD thesis also reports a new method to perform mercury compound specific isotopic analysis (CSIA) using a gas chromatography fitted with a PTV injector (GC-PTV) coupled to the MC-ICP-MS. This allows the isotopic analysis of several species with external precisions ranging from 0.30 to 0.40‰ (2SD) for mercury concentration down to 150 ng.L-1 in biological samples.The analytical developments proposed in this PhD thesis allows to automatically and directly measure mercury isotopic compositions at ultra-trace levels (down to 5 ng.L-1) while keeping precision compatible with main environmental questions. This will allow to analyze environmental compartment containing very low amount of mercury (natural waters, planktons,…) and then open new perspectives for a better understanding of the bio-geochimical cycle of mercury

A fit-for purpose procedure for lead isotopic ratio determination in crude oil, asphaltene and kerogen samples by MC-ICPMS

cited By 7International audienceLead isotopic ratios have been used extensively in geological, geochronological, and archaeological studies. However, the classical anion exchange method for Pb isolation/purification using AG1-X8 resin cannot be directly adopted for high content organic samples such as crude oils, due to the fact that the sample matrices probably interact with the active sites in the resin. This results in low percentages of Pb being recovered during column separation and low-level sample purity, therefore affecting the precision of the MC-ICPMS isotopic ratio. For Pb isolation/purification from crude oil samples, at least 0.5 mL of the resin AG1-X8 is required to obtain high Pb recovery without fractioning during the analysis of crude oil. After evaluation of 5 different mass bias correction methods, the combination of Tl normalisation (exponential law) and standard bracketing was selected, providing a precision of 0.0039, 0.0014 and 0.0012 and accuracies (‰) of 0.001, 0.001 and 0.004 for 208/204Pb, 207/204Pb and 206/204Pb isotope ratios, respectively, in the analysis of a solution of 10 ng mL -1 SRM NIST 981 (n = 18). The proposed procedure allows the reliable determination of Pb isotope ratio in crude oil, asphaltene and kerogen samples, important in geochronological studies. © 2012 The Royal Society of Chemistry

Isotopic Analysis via Multi-Collector Inductively Coupled Plasma Mass Spectrometry in Elemental Speciation

International audienceThis chapter contains sections titled:IntroductionAdvantage of On‐Line versus Off‐Line Separation of Elemental SpeciesCoupling Chromatography with MC‐ICP‐MSEnvironmental and Other ApplicationsConclusion and Future TrendsReference

Fast and precise method for Pb isotope ratio determination in complex matrices using GC-MC-ICPMS: Application to crude oil, Kerogen, and asphaltene samples

cited By 6International audienceA new method to determine Pb isotope ratio without ion-exchange-matrix separation is proposed. After acid digestion, Pb was ethylated to Et 4Pb, separated from the digested solution (black shale, asphaltene, crude oil and kerogen) by extraction in isooctane, and then injected into a gas chromatograph coupled to a multicollector inductively coupled plasma mass spectrometer. Seven isotopes (202Hg, 203Tl, 204Pb, 205Tl, 206Pb, 207Pb, 208Pb) were monitored simultaneously with peak duration of 23 s. GC elution was operated under wet plasma conditions where a thallium standard solution was introduced to the mass spectrometer for mass bias correction. The total time of the procedure (sample preparation and analysis, after acid digestion) was reduced by a factor of 15 compared to conventional-continuous sample introduction. Data treatment was carried out using the linear regression slope method. Mass bias was corrected using the double correction method (first thallium normalization followed by classical bracketing). For the 208/206Pb and 207/206Pb ratios, precision (2RSD EXT, n = 21) was 49 and 69 ppm, and the bias between experimental results and reference values was better than 0.0033 and 0.0007 %, when injecting 1.2 ng of ethylated Pb SRM NIST 981 solution. Results obtained by this method were validated by comparison with those obtained via conventional-continuous sample introduction. The applicability of this approach was demonstrated with the analysis of black shale, asphaltene, crude oil and kerogen samples. © 2012 American Chemical Society

Hg in Arctic top predators: insights from a captive experiment on hooded seals Cystophora cristata.

Arctic predators like true seals have been experiencing a strong increase in Hg levels in their tissues in the last 150 years. This is in contrast with other terrestrial animals or other parts of the world. Dietary Hg accumulates and biomagnifies in marine food webs in its most toxic form, monomethylmercury (MMHg). Hg seven stables isotopes (196Hg, 198Hg, 199Hg, 200Hg, 201Hg, 202Hg and 204Hg) undergo both mass-dependent and mass-independent fractionation (MDF and MIF, respectively) as a result of abiotic and biotic reactions occurring in the environment and within the organism. For this reason, they are a promising tool for tracing Hg cycling in the natural environment. The interpretation of Hg isotopic data remain however a challenge, especially when taking into account species such as Arctic true seals, which have highly complex life styles and metabolism. In 2012, six pups of hooded seals Cystophora cristata were captured on the ice edge of the Greenland Sea and kept in captivity for 2 years. During this period, they were fed on a constant diet made of Norwegian herring Clupea harengus and vitamin complements. This allowed us to study Hg kinetic in an Arctic top predator without the influence of age, distribution and diet specialization. The main objective was to select the tissue in which the information about Hg pathways would be conserved, leading to the optimal tracing of Hg sources along the food web. Total Hg (THg) concentrations were determined on a Milestone direct mercury analyzer, while MeHg and IHg concentrations were determined by isotope dilution-gas chromatography-inductively coupled plasma-mass spectrometer (ID-GC-ICP-MS) following microwave-assisted extraction and aqueous phase derivatization. Mercury isotopic composition analysis was performed using cold vapor generation (CVG) with multicollector-inductively coupled plasma-mass spectrometer (MC-ICP-MS, Nu Instruments). The analysis was conducted in seal muscle, liver, hair, and kidney, plus muscle of herring. Hg speciation changed significantly among tissues. Hair and muscle were predominantly enriched in MMHg (range: 84 to 98% and 74 to 95%, respectively) relative to liver and kidney (range: 7 to 38% and 4 to 27% respectively) that tend to mainly accumulate iHg. δ202Hg values were positively related with levels of MMHg (p > 0.0001, R2 = 0.531). With higher values found in hair, followed by muscle, liver and kidney. Δ199Hg and Δ201 values were not influenced by Hg species composition in tissues, as well as slope values of Δ199Hg/Δ201Hg. The low fraction of MMHg (< 30%) found in liver and kidney determines a large variability of isotopic and contamination values. When calculating the isotopic trophic enrichment between herring and hooded seals’ tissues, a significant 202Hg enrichment resulted between seal hair and kidney and herring (p = 0.011 and p < 0.001), indicating important MDF between the ingested prey and these tissues. Instead, a significant MIF (Δ199Hg and Δ201 values) was observed only between seals’ kidney and herring (p = 0.0003). Our results show that: (1) Hg isotopic composition reflects Hg molecular speciation; (2) as a result of isotopic incorporation during tissue turnover, hair and kidney present a strong trophic MDF; and (3) with the exception of kidney, MIF signal is conserved in all tissues during assimilation of prey items. Based on these observations, we believe that muscle is the optimal monitoring tissue for tracing of Hg sources since both the MDF and MIF signals are conserved from prey to predator. The important MDF observed in hair instead, make this tissue the best option for the analysis of Hg biomagnification along food webs.SODYMAR

Monitoring of Hg sources in Arctic top predators: insights from isotopic analysis in captive hooded seals Cystophora cristata.

peer reviewedaudience: professional, studentArctic predators like true seals have been experiencing a strong increase in Hg levels in their tissues in the last 150 years. This is in contrast with other terrestrial animals or other parts of the world. Dietary Hg accumulates and biomagnifies in marine food webs in its most toxic form, monomethylmercury (MMHg). Hg seven stables isotopes (196Hg, 198Hg, 199Hg, 200Hg, 201Hg, 202Hg and 204Hg) undergo both mass-dependent and mass-independent fractionation (MDF and MIF, respectively) as a result of abiotic and biotic reactions occurring in the environment and within the organism. For this reason, they are a promising tool for tracing Hg cycling in the natural environment. The interpretation of Hg isotopic data remain however a challenge, especially when taking into account species such as Arctic true seals, which have highly complex life styles and metabolism. In 2012, six pups of hooded seals Cystophora cristata were captured on the ice edge of the Greenland Sea and kept in captivity for 2 years. During this period, they were fed on a constant diet made of Norwegian herring Clupea harengus and vitamin complements. This allowed us to study Hg kinetic in an Arctic top predator without the influence of age, distribution and diet specialization. The main objective was to select the tissue in which the information about Hg pathways would be conserved, leading to the optimal tracing of Hg sources along the food web. Total Hg (THg) concentrations were determined on a Milestone direct mercury analyzer, while MeHg and IHg concentrations were determined by isotope dilution-gas chromatography-inductively coupled plasma-mass spectrometer (ID-GC-ICP-MS) following microwave-assisted extraction and aqueous phase derivatization. Mercury isotopic composition analysis was performed using cold vapor generation (CVG) with multicollector-inductively coupled plasma-mass spectrometer (MC-ICP-MS, Nu Instruments). The analysis was conducted in seal muscle, liver, hair, and kidney, plus muscle of herring. Hg speciation changed significantly among tissues. Hair and muscle were predominantly enriched in MMHg (range: 84 to 98% and 74 to 95%, respectively) relative to liver and kidney (range: 7 to 38% and 4 to 27% respectively) that tend to mainly accumulate iHg. δ202Hg values were positively related with levels of MMHg (p > 0.0001, R2 = 0.531). With higher values found in hair, followed by muscle, liver and kidney. Δ199Hg and Δ201 values were not influenced by Hg species composition in tissues, as well as slope values of Δ199Hg/Δ201Hg. The low fraction of MMHg (< 30%) found in liver and kidney determines a large variability of isotopic and contamination values. When calculating the isotopic trophic enrichment between herring and hooded seals’ tissues, a significant 202Hg enrichment resulted between seal hair and kidney and herring (p = 0.011 and p < 0.001), indicating important MDF between the ingested prey and these tissues. Instead, a significant MIF (Δ199Hg and Δ201 values) was observed only between seals’ kidney and herring (p = 0.0003). Our results show that: (1) Hg isotopic composition reflects Hg molecular speciation; (2) as a result of isotopic incorporation during tissue turnover, hair and kidney present a strong trophic MDF; and (3) with the exception of kidney, MIF signal is conserved in all tissues during assimilation of prey items. Based on these observations, we believe that muscle is the optimal monitoring tissue for tracing of Hg sources since both the MDF and MIF signals are conserved from prey to predator. The important MDF observed in hair instead, make this tissue the best option for the analysis of Hg biomagnification along food webs.SODYMAR

Hg speciation and stable isotopic composition in marine mammals: new insights and perspectives

Mercury (Hg) is a persistent toxic compound whose amount in the global biosphere has at least tripled since industrialization. Recently, the study of the seven Hg stable isotopes has emerged as a new promising technique affording to explore the Hg cycle both in situ and in laboratory. Mercury stable isotopes display both mass dependent fractionation (MDF, reported as δ202Hg) and mass independent fractionation (MIF, reported as Δ199Hg and Δ201Hg). Our recent findings about Hg accumulation in the European seabass, Dicentrarchus labrax, showed how the combination of Hg isotopic values with Hg speciation allow tracing back Hg environmental sources as well as metabolic pathways within the organisms. However, such interpretation gets more complicated in more physiologically complex animals such as seals. With the aim of study basal Hg kinetic in an top predator without the influence of distribution and diet specialization, we measured T-Hg levels, speciation and isotopic composition in 6 captive pups of hooded seals, Cystophora cristata, and their diet the Norwegian herring Clupea harengus. The main objective was to select the tissue in which the information about Hg pathways would be conserved, leading to the optimal tracing of Hg sources along the food web. MMHg ranged between 84 to 98% in hair, 74 to 95% in muscle, 7 to 38% in liver and 4 to 27% in kidney. A significant 202Hg enrichment resulted between seal hair and herring (p = 0.011), indicating important MDF between the ingested prey and these tissues. Instead, a significant MIF (Δ199Hg and Δ201 values) was observed only between seals’ kidney and herring (p = 0.0003). Our results showed that hair represents the best tissue for the analysis of Hg biomagnification along food webs; and that with the exception of kidney, MIF signal is conserved in all tissues during assimilation of prey items.SODYMAR

Do sicydium punctatum adults move in the Caribbean estuaires? New insight from strontium isotopes

cited By 0International audienceStrontium isotopic variations (87Sr:86Sr) were investigated in otoliths of an amphidromous goby, Sicydium punctatum, coming from a tropical insular river and showing contrasted depositional patterns of barium:calcium in otolith (Ba:Caotolith). In our study, varying as well as non-varying Ba:Caotolith individuals exhibited unchanged 87Sr:86Srotolith throughout the adult phase with values typical of stream water flowing through volcanic substrate (0.7053 ± 0.0003). These results unambiguously discard the Ba:Caotolith peaks as markers of migrations between freshwater and brackish estuarine water during the adult phase of the species and open on investigations of sources of variations on microhabitats or unknown physiological effects