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The development of collision-cell multi-collection inductively-coupled-plasma mass-spectrometers has revolutionized K isotope chemistry, improving the sensitivity by over a factor of 10 compared to that of older generation instruments. The application of isotope chemistry of metals in medical science (isotope metallomics) has shown significant growth in the last few years with respect to the study of metal cycles in the body and/or as diagnostic tools for diseases affecting metal homeostasis. Given the major role that K plays in biology through the preservation of cellular homeostasis itself, the generation of nervous impulses, and the formation of glycogen in the liver, the development of K isotope metallomics is imminent and necessary. To this end, we report the first set of high precision K isotopic data for numerous widely available biological reference materials, spanning both land and sea animals, as well as various bodily organs (muscle, kidneys, and liver). Results indicate that land animals are globally enriched in the lighter isotopes compared to sea animals, and that K isotopes are fractionated by more than 1.5‰ between organs (bovine), highlighting that K isotopes could be used to study K cycles within the body. These novel data—and reference materials—could be used for future interlaboratory comparisons.

Copper (Cu) stable isotopes are useful for understanding pathways and tracing changes in Cu homeostasis, such as those induced by various diseases (e.g. liver cirrhosis, numerous forms of cancer, and neurodegenerative diseases). However, this utility relies on a baseline understanding of the natural distribution of Cu isotopes between organs of healthy organisms, which is not well-known at present. Here, the distribution of natural Cu isotopes in the brain, liver, red blood cells, plasma, kidneys, and muscle of 14 mice (7 males and 7 females) from three different genetic backgrounds is assessed. We show that the Cu isotopic composition of most mouse organs is isotopically distinct from one another. The most striking feature is the heavy isotope enrichment of the kidney (δ65Cu = 1.65 ± 0.06‰, 2SE), brain (δ65Cu = 0.87 ± 0.03‰, 2SE) and liver (δ65Cu = 0.71 ± 0.24‰, 2SE) compared to blood components, i.e. red blood cells (RBCs) (δ65Cu = 0.30 ± 0.06‰, 2SE), and plasma (δ65Cu = –0.61 ± 0.08‰, 2SE), with δ65Cu being the per mil deviation of the 65Cu/63Cu ratio from the NIST SRM 976 standard. Differences in genetic background do not appear to affect the isotopic distribution of Cu. Interestingly, male and female mice appear to have different Cu concentrations and isotopic compositions in their brain, plasma, muscle, and RBC. By demonstrating that organs have distinct isotopic compositions, our study reinforces the notion that Cu stable isotopes can be used to trace changes in homeostasis in diseases affecting Cu distribution, such as Alzheimer's disease, liver cancer, and possible chronic kidney failure.

International audience; Mass-dependent K isotopic fractionations can be used to trace cosmochemical, geological, and biological processes such as evaporation/condensation, core formation, magmatic processes, weathering, and cellular metabolism. However, the application of stable K isotopes has been limited by major isobaric interferences from Ar, common on conventional multi-collector inductively-coupled-plasma mass-spectrometer (MC-ICP-MS), particularly for the low-K samples. Here, we present a set of high-precision K isotopic data acquired on terrestrial rocks, seawater, as well as a lunar meteorite using the recently released Nu Sapphire™ MC-ICP-MS that utilizes a collision cell to minimize Ar based interferences while maintaining remarkably high K sensitivity (≈ 2000 V/ppm). The influence of several parameters on the precision and accuracy of the K isotopic data has been evaluated, including total K concentration, K intensity mismatch between sample and standard, HNO3 molarity mismatch between sample and standard, and the presence of matrix elements. We found that the Nu Sapphire™ can be used to acquire precise and accurate data using as little as 125 ng of K, which represents an improvement by a factor 10 compared to what has been done on previous instruments. We present data for 23 previously analyzed samples; these data are highly consistent with literature values. On the other hand, accurate measurements are conditioned 1) to the close matching of sample and standard K intensities (a 1% mismatch creates a 0.02‰ offset on the 41K/39K ratio), and 2) to the absence of Ca (a Ca/K ratio of 1% creates a 0.069‰ offset on the 41K/39K ratio). In addition, Rb/K, Na/K, Ti/K and Cr/K ratio should also be maintained under 2.5% to avoid isotopic offset.We confirm the existence of significant mass-dependent K isotopic variations in terrestrial samples and that lunar rocks are isotopically heavier than terrestrial rocks. The incomparable sensitivity offered by the Nu Sapphire opens the possibility for high-precision K isotopic measurements across a wide range of samples for diverse applications.

International audience; In this study, we quantify zinc isotope fractionation during its sorption onto kaolinite, by performing experiments under various pH, ionic strength, and total Zn concentrations. A systematic enrichment in heavy Zn isotopes on the surface of kaolinite was measured, with Delta Zn-66(adsorbed-solution) ranging from 0.11 parts per thousand at low pH and low ionic strength to 0.49 parts per thousand at high pH and high ionic strength. Both the measured Zn concentration and its isotopic ratio are correctly described using a thermodynamic sorption model that considers two binding sites: external basal surfaces and edge sites. Based on this modeling approach, two distinct Zn isotopic fractionation factors were calculated: Delta Zn-66(adsorbed-solution) = 0.18 +/- 0.06 parts per thousand for ion exchange onto basal sites, and Delta Zn-66(adsorbed-solution) = 0.49 +/- 0.06 parts per thousand for specific complexation onto edge sites. These two distinct factors indicate that Zn isotope fractionation is dominantly controlled by the chemical composition of the solution (pH, ionic strength)

Rationale During transient signal acquisition by Multi-Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS), an isotope ratio increase or decrease (isotopic drift hereafter) is often observed which is related to the different time responses of the amplifiers involved in multi-collection. This isotopic drift affects the quality of the isotopic data and, in a recent study, a method of internal amplifier signal synchronization for isotope drift correction was proposed. In this work the determination of the amplifier time constants was investigated in order to validate the method of internal amplifier signal synchronization for isotope ratio drift correction. Methods Two different MC-ICPMS instruments, the Neptune and the Neptune Plus, were used, and both the lead transient signals and the signal decay curves of the amplifiers were investigated. Results Our results show that the first part of the amplifier signal decay curve is characterized by a pure exponential decay. This part of the signal decay was used for the effective calculation of the amplifier first-order time constants. The small differences between these time constants were compared with time lag values obtained from the method of isotope signal synchronization and were found to be in good agreement. Conclusions This work proposes a way of determining amplifier first-order time constants. We show that isotopic drift is directly related to the amplifier first-order time constants and the method of internal amplifier signal synchronization for isotope ratio drift correction is validated. Copyright © 2015 John Wiley & Sons, Ltd.

Isotopic variation for traditional elements (H, C, N, O and S) has been widely used in the past 40 years in Earth and planetary sciences to study many processes with an emphasis on environments where fluids are present (e.g., Valley and Cole 2011). More recent developments have allowed high-precision measurements of isotope ratios of what has been called non-traditional elements (i.e., Mg, Si, Fe, Zn, Cu, Mo), which are usually less fractionated than traditional elements by at least an order of magnitude (see this volume). These non-traditional stable isotopes can give insights on processes where fluids are not present (e.g., metal–silicate fractionation, e.g., Georg et al. 2007 and review by Poitrasson et al. 2017, this volume), evaporation processes during planetary formation (e.g., Paniello et al. 2012, Wang and Jacobsen 2016, and review by Moynier et al. 2017 this volume), igneous differentiation (e.g., Williams et al. 2009; Sossi et al. 2012; and review by Dauphas et al. 2017, this volume), and on biological processes (e.g., Walczyk and von Blanckenburg 2002, and review by Albarede et al. 2017 this volume). Among all these non-traditional isotopic systems, Mg isotopes are of major importance because (i) Mg is a major constituent of the silicate portion of planetary bodies, (ii) Mg has more than two isotopes (24Mg, 25Mg and 26Mg) allowing to study processes leading to various types of mass fractionation (Young et al. 2002; Young and Galy 2004; Davis et al. 2015) and (iii) 26Mg excesses produced by the radioactive decay of short-lived 26Al (T1/2=0.73 Ma) (Lee et al. 1976) are a key tool for early Solar system chronology (see reviews by Dauphas and Chaussidon 2011; Chaussidon and Liu 2015). Note that in addition, significant Mg isotopic …

Lithium (Li) isotopes are a promising tracer of chemical weathering processes for both modern and ancient times. In order to improve the use of Li isotopes in the sedimentary record, here we calibrate the relationship between weathering intensity and detrital Li isotope composition (δ7Li) using the fine fraction of modern large river sediments. Through independent estimates for sediment provenance to calculate the Li isotope signature of the rock from which the sediments derive through weathering, we show that source rock variability (in particular the relative contribution of sedimentary versus igneous rocks) must be corrected for before using Li isotopes as a weathering proxy. We also show that for rivers draining mountain ranges, the contribution to river sediments of particles derived from sedimentary rocks is correlated to their Li/Al ratio, making it possible to use Li contents to estimate the average source rock composition. Once corrected for bedrock variability, the Li isotope signature defines a negative relationship with the weathering intensity (ratio between silicate weathering rate and total denudation rate), with highest Li isotope fractionation for the highest weathering intensity. Altogether, we propose a set of new relationships between weathering, erosion, provenance, and Li isotopes that can be used to quantify present-day and paleo-weathering using detrital sediment.

cited By 15; International audience; The measurement of isotope ratios by Multi Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) in transient signals often shows a drift of the isotope signal ratio during signal acquisition. This "isotopic drift" is generally related to the small and distinct time lags between the responses of the amplifiers involved in the Faraday detector configuration. In this work, a method of synchronization of transient isotope signals for a duration of a few tens of seconds is proposed in order to: (1) quantify the time lags between the amplifiers using the ratios of the raw isotope signals and (2) correct the isotope ratio drifts. The method was successfully tested on lead isotope ratio measurements obtained from two different multi-collector mass spectrometers and setups (flow injection with direct injection and gas chromatography). This approach offered a precise determination of the time lag between the different amplifier systems and an effective correction of the isotope ratio drift. The performances of the methods traditionally used for isotope ratio calculation of transient signals were also compared before and after isotope ratio drift correction. This journal is © the Partner Organisations 2014.

Twenty-nine analogs of indirubin, an isomer of indigo, have been synthesized to optimize its promising kinase inhibitory scaffold. These compounds being also pigmented, have been tested for their photoreactivity. Absorption maxima were between 485 nm and 560 nm. Addition of fetal calf serum induced fluorescence and time dependent absorption modifications. Appropriate illumination induced Reactive Oxygen Species (ROS) production for nineteen compounds out of twenty-nine. The relationship between fluorescence and ROS production is discussed. Six compounds showed an important toxicity on F98 cells, a murine glioma cell line. Three of these were found to be also phototoxic, as four other non-toxic compounds. All but onze phototoxic compounds were detected as ROS producers by in vitro tests. Photoreactivity assessment is important to anticipate adverse reactions for compounds that might be clinically developed. The experimental assay was found to be the only way to evaluate the photoreactivity of this family of compounds since no predictive criteria on structures could be found. Combining the vascular tumor growth inhibition induced by kinase inhibitors with the massive local blood flow arrest following photodynamic treatment may be an efficient anti-cancer strategy. These data could orientate further syntheses of either non-photoreactive compounds or compounds displaying both kinase inhibitory activity and strong phototoxicity.

High-precision stable Ba isotope ratios are reported in a variety of terrestrial samples, undifferentiated primitive meteorites, and calcium–aluminum-rich inclusions (CAIs) from the Allende chondrite. All whole-rock terrestrial and meteorite samples are isotopically indistinguishable at a 50 parts per million (ppm) level per atomic mass unit (amu). Three CAIs are isotopically light, with δ138/137Ba (permil deviation of the 138Ba/137Ba ratio from a terrestrial standard) values down to − 0.6‰ compared to whole-rock meteorites, whereas the matrix is enriched in heavy isotopes (δ138/137Ba: + 0.2‰). Similar light isotope enrichments in CAIs have been previously observed for Eu, Sr, and Ca, while for most other elements CAIs are enriched in the heavier isotopes (e.g. Mg, Fe). Kinetic isotopic fractionation is a possible explanation for the enrichment in the lightest isotopes, either by condensation from a vapor phase enriched in light isotopes by kinetic effects or by kinetic fractionation during non-equilibrium condensation of an undercooled gas as suggested for Ca isotopes. However, the common property of Ba, Eu, and Sr is that they all have a low first ionization potential. We suggest that electromagnetic sorting of ionized species in the early Solar System is a possible alternative mechanism to explain the depletion in heavy isotopes observed in refractory inclusions for those elements.

During transient signal acquisition by Multi-Collection Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS), an isotope ratio increase or decrease (isotopic drift hereafter) is often observed which is related to the different time responses of the amplifiers involved in multi-collection. This isotopic drift affects the quality of the isotopic data and, in a recent study, a method of internal amplifier signal synchronization for isotope drift correction was proposed. In this work the determination of the amplifier time constants was investigated in order to validate the method of internal amplifier signal synchronization for isotope ratio drift correction.Two different MC-ICPMS instruments, the Neptune and the Neptune Plus, were used, and both the lead transient signals and the signal decay curves of the amplifiers were investigated.Our results show that the first part of the amplifier signal decay curve is characterized by a pure exponential decay. This part of the signal decay was used for the effective calculation of the amplifier first-order time constants. The small differences between these time constants were compared with time lag values obtained from the method of isotope signal synchronization and were found to be in good agreement.This work proposes a way of determining amplifier first-order time constants. We show that isotopic drift is directly related to the amplifier first-order time constants and the method of internal amplifier signal synchronization for isotope ratio drift correction is validated.

International audience; To improve the precision of isotope analyses of low ion intensities using the Faraday detection system, amplifiers equipped with 10(12) Omega resistors (hereafter 10(12) Omega amplifiers) have been developed. While the behavior of these amplifiers for steady signals has been well investigated, there is no ample evidence regarding the use of 10(12) Omega amplifiers for transient signal acquisition. In this work, we investigated the simultaneous use of amplifiers equipped with 10(12) Omega and 10(11) Omega resistors for transient signal acquisition. Using the equation describing the relationship between the input ion current and the output voltage in the amplifiers, we showed how the transient signal duration influences the accuracy of the isotope ratio measurements. In particular, lead transient signals were investigated using a Neptune Plus MC-ICPMS and Pb-204 and Pb-206 isotopes were measured using 10(12) Omega and 10(11) Omega amplifiers, respectively. The Pb-204/Pb-206 isotope ratio showed an important drift due to a large time lag between 10(12) Omega and 10(11) Omega amplifiers. The time lag was quantified (0.175(3) s) and the isotopic drift was corrected using a method of internal signal synchronization. The Pb-204/Pb-206 drift corrected data obtained from the 10(12)-10(11) Omega amplifier configuration were compared to the data obtained from 10(11)-10(11) Omega amplifiers. Our results point out that for low transient signal intensities (

International audience; This work presents a fully automated setup for using direct injection nebulization as an introduction system for solution measurements by MC-ICP-MS, here applied to boron isotopes in pure boric acid solutions and natural samples. In this setup, a direct injection nebulizer (d-DIHEN) is plugged into the plasma torch without any spray chamber, and an automated 6-port valve interfaces the nebulizer and the autosampler. The advantages of a d-DIHEN for boron isotope ratio measurements are high sensitivity and short washout times, allowing for sample-standard bracketing (SSB) measurements at a higher rate than spray chambers. The measurement of boron isotopes by MC-ICP-MS at an unprecedented sub 0.1 parts per thousand, repeatability level (2 standard deviation = 2SD) was achieved for pure boric acid solutions. The improved precision is allowed by a better stability of the introduction system with continuous operation of the peristaltic pump (which was manually switched off between samples before automation) and due to the possibility of multiple analyses of the same sample solution. However, such a good repeatability was not systematically obtained for boron isotopes SSB measurements of natural samples (in fine 2SD are between 0.02 and 0.5 parts per thousand). Boron from natural samples has to be extracted before isotope analysis, with one to four steps depending on the sample type. Repeated analyses of boron independently separated up to ten times from the same sample lead to an external reproducibility no better than 0.2 parts per thousand. Boron chemical separation from the samples prior to MC-ICP-MS analyses seems to remain the main limitation to precise measurements of boron isotope ratios.

International audience; In the research field concerning the nuclear transmutation of long-lived radionuclides, numerous isotopically enriched elements have been irradiated in the Phe´nix French reactor in order to determine basic neutronic data. The precise and accurate measurement of isotopic composition of these elements after irradiation is of prime interest. Among these elements, the 95Mo target presents an interesting analytical challenge as the irradiation generates, among others, the interfering isotopes 92Mo and 92Zr. A method using multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS) has been developed for the precise measurement of Mo isotope composition in natural Mo and 95Mo enriched samples solutions in the presence of Zr isobaric interferences. The Mo/Zr separation was performed in situ by injecting N2O as a reaction gas in the collision–reaction cell of the instrument. The reason why a selective chemical reaction of Zr+ with N2O forms mainly ZrO2+ product whereas Mo is not reactive, is explained. This technique leads to an efficient separation of Mo and Zr, reflected by the similar accuracy and uncertainty obtained for natural and isotopically enriched Mo isotope composition with and without Zr addition. This study demonstrates the capability of the collision–reaction cell of the MC-ICPMS to separate efficiently Mo and Zr, instead of using chemical separation techniques, and to produce precise and reproducible Mo isotopic data.