Precise Isotopic Analysis Research Articles

Fast and precise boron isotopic analysis of carbonates and seawater using Nu Plasma II multi-collector inductively coupled plasma mass spectrometry and a simple sample introduction system.

The boron (B) isotopic composition in marine carbonates provides important insights into paleoclimate reconstruction and biomineralization. However, precise and accurate measurements of B isotopes using plasma-based mass spectrometry is difficult due to the volatile nature of B, which typically requires complex and more specialized sample introduction systems. Existing analytical protocols have mostly been based on Thermo Scientific Neptune Plus multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) instruments, whereas methods based on Nu Plasma mass spectrometers are scarce. We have developed a simplified analytical protocol using Nu Plasma II MC-ICPMS with standard glass sample introduction systems. Boron extraction and purification were conducted using a two-stage column chemistry with cation-exchange and Amberlite IRA 743 B-specific resin. A sample drying step was avoided, which allows for direct isotopic analysis after column chemistry. A wet plasma mode with a standard glass cyclonic spray chamber and a glass nebulizer was used instead of a more specialized perfluoroalkoxy (PFA) sample introduction system. Low residual B signals were achieved with a relatively short period of wash-out with 0.5 N HNO3 . The external precision is better than 0.30‰ (2SD) calculated from the long-term bracketing standard, NIST SRM 951a. The overall robustness of the method was demonstrated by measurements of the international carbonate standard JCp-1 (δ11 B = +24.49 ± 0.36‰, 2SD) and seawater (δ11 B = +39.98 ± 0.35‰), which are consistent with reported values. Our method provides an alternative approach for B isotope analysis using a routine wet plasma MC-ICPMS setup that can facilitate geochemical and environmental application of B isotopes.

In situ calcium isotopic ratio determination in calcium carbonate materials and calcium phosphate materials using laser ablation-multiple collector-inductively coupled plasma mass spectrometry

This study presents a highly precise and accurate Ca isotope analysis method using laser ablation multiple collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) in calcium carbonates and calcium phosphates. High-sensitivity cones and nitrogen gas were used to improve the performance of the LA-MC-ICP-MS. The experiment results show that at the N2 mode, the signal intensity of 44Ca+ in the high-sensitivity cones (Jet + X cones) was 5-fold higher than that in the normal cones (S + H cones), while the polyatomic interferences of 40Ar1H1H+ and 40Ar16O+ in the high-sensitivity cones were suppressed by factors of 6.1 and 10.6, respectively, after the addition of 8 ml min−1 N2. The combination of high sensitivity cones and N2 addition did not increase the production of double charged ions. Additionally, the interference correction of doubly charged Sr ions was investigated in detail. The experiment results demonstrate that the concentration ratio of Sr to Ca (represented as I87Sr++/I44Ca+), the 87Sr/86Sr ratio and the mass fractionation factor of Sr (fSr) during the measurement process were key parameters for in situ Ca isotope ratios analysis. The threshold values of these key parameters were evaluated and are recommended to ensure an accurate correction of doubly charged Sr ions. Using the optimized instrumental conditions and correction strategies, an excellent within-run precision (<0.06‰, 2SE) and external reproducibility (<0.15‰, 2SD) for the microanalysis of δ44/42Ca915b were obtained in natural calcium carbonates and calcium phosphates. These precisions are better than the values previously reported in the literature regarding using LA-MC-ICP-MS. Matrix effects were observed during the in situ Ca isotope analysis among calcium carbonates, hydroxy calcium phosphates and igneous apatites. Using the matrix-matching standards, accurate δ44/42Ca915b values in natural materials with various matrices were achieved, confirming the availability of the proposed method to resolve the spatial variation of δ44/42Ca in natural materials.

Calcium isotope fractionation during magmatic processes in the upper mantle

Abstract The Earth’s mantle has a complex history of partial melting and melt-peridotite reaction that have redistributed Ca and other elements between residues and melting products. Given the considerable Ca isotopic variation reported in mantle rocks, evaluation of the fractionation of stable Ca isotopes in magmatic processes in the mantle is critical to decode mantle evolution and the effect of recycled materials. We have performed precise and accurate Ca isotopic analyses on a series of well-characterized spinel-facies mantle peridotites (lherzolite, harzburgite and dunite, n = 29), pyroxenites (websterite, clinopyroxenite and orthopyroxenite, n = 15) and their mineral constituents (n = 8) from the Balmuccia and Baldissero peridotite massifs of the Ivrea Zone in the Italian Alps. These peridotites underwent variable degrees of melting and melt-peridotite reaction, whereas the pyroxenites are mainly the products of melt-peridotite reaction and crystallization of migrating basic melts from the asthenosphere. The lherzolites from Balmuccia and Baldissero show δ44/40Ca values of 0.94 ± 0.11‰ (2sd, n = 22), which are uniform within long-term external reproducibility (±0.14‰, 2sd). The δ44/40Ca values of the harzburgites (0.83‰ to 0.92‰) do not differ from those of lherzolites, including those with a history of intensive melt-peridotite reaction to form replacive dunites. The websterites and spinel clinopyroxenites display δ44/40Ca of 0.86 ± 0.10‰ (n = 14), within the range of the lherzolites and harzburgites. The indistinguishable δ44/40Ca among these very diverse mantle rocks is the consequence of the overwhelming control of stable Ca isotopes by clinopyroxene in the magmatic processes involved, because clinopyroxene dominates the budget of Ca (>90% for harzburgites; 93% to 99% for lherzolites, websterites and clinopyroxenites). Only the clinopyroxene-poor ( 25% melting and replacive dunites tend to display slightly heavier Ca isotopic compositions. Consequently, irrespective of their magmatic history, most fertile mantle rocks from different geological settings display a homogenous Ca isotope composition, summarized as, δ44/40Ca of 0.94 ± 0.10‰ (2sd, n = 47) for the Earth’s mantle. The deviations in Ca isotopic variations observed in other mantle rocks may be attributed to kinetic isotope fractionation and metasomatism by melts with isotopic compositions influenced by recycled crustal materials.

Concerns about Quadrupole ICP-MS Lead Isotopic Data and Interpretations in the Environment and Health Fields.

There has been a massive increase in recent years of the use of lead (Pb) isotopes in attempts to better understand sources and pathways of Pb in the environment and in man or experimental animals. Unfortunately, there have been many cases where the quality of the isotopic data, especially that obtained by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS), are questionable, resulting in questionable identification of potential sources, which, in turn, impacts study interpretation and conclusions. We present several cases where the isotopic data have compromised interpretation because of the use of only the major isotopes 208Pb/206Pb and 207Pb/206Pb, or their graphing in other combinations. We also present some examples comparing high precision data from thermal ionization (TIMS) or multi-collector plasma mass spectrometry (MC-ICP-MS) to illustrate the deficiency in the Q-ICP-MS data. In addition, we present cases where Pb isotopic ratios measured on Q-ICP-MS are virtually impossible for terrestrial samples. We also evaluate the Pb isotopic data for rat studies, which had concluded that Pb isotopic fractionation occurs between different organs and suggest that this notion of biological fractionation of Pb as an explanation for isotopic differences is not valid. Overall, the brief review of these case studies shows that Q-ICP-MS as commonly practiced is not a suitable technique for precise and accurate Pb isotopic analysis in the environment and health fields.

Precise isotope analysis of tellurium by inductively coupled plasma mass spectrometry using a double spike method

We present an analytical protocol to determine the Te/Se ratio and stable isotope composition of Te from a single sample aliquot.

Precise carbon isotopic ratio analyses of micro amounts of carbonate and non-carbonate in basalt using continuous-flow isotope ratio mass spectrometry.

Continuous-flow isotope ratio mass spectrometry (CF-IRMS) is a specialized technique used to quickly analyze very small amounts of sample. We have used CF-IRMS to assess the influences of sample weight and relative carbon content on the accuracy and precision of the δ13 C values of micro amounts of carbonate and non-carbonate in silicate rocks. The analytical work was performed on a Gasbench II (GB) sample preparation device and on an Elemental Analyzer (EA), which were both interfaced to CF-IRMS instruments. Potential silicate matrix effects on the carbon isotopic analyses were investigated by measuring mixtures of calibrated carbon reference materials and quartz powder. The calibration lines, established by the measured raw values and the known values of three reference materials mixed with quartz powder, were used to calibrate the δ13 C values of basalt samples from eastern China. The δ13 C values measured by GB-CF-IRMS of one national carbonate reference material, GBW04416, deviate slightly from the known value for approximately 20-70μg of carbonate contained in 4.5-mL vials; the smaller the sample size, the lower the measured δ13 C values. External precision better than 0.1‰ (1σ, n=26) is achieved at a signal intensity for mass 44 of between 868 and 1614mV, corresponding to a sample weight of 30.8-50.2μg, whereas it is reduced to 0.27‰ (1σ, n=34) at a signal intensity between 519 and 1614mV, corresponding to a sample weight of 21.1-50.2μg. In the EA-CF-IRMS experiments for non-carbonate carbon, at high carbon concentration (greater than 800ppm) and at optimum sample weights, the accuracy and precision are both better than 0.2‰. For carbon concentrations less than 500ppm, the measured δ13 C values deviate from the average by up to -1.2‰ and the precision is 0.74‰. The measured δ13 C values decrease substantially at lower carbon concentration and higher sample weights, and poorer precision is obtained. Suggestions are made to measure repeatedly the same carbon concentration of sample and reference materials in order to obtain not only reproducible, but also accurate carbon isotope ratios.

Precise selenium isotope measurement in seawater by carbon-containing hydride generation-Desolvation-MC-ICP-MS after thiol resin preconcentration

The isotopic compositions of Se in natural materials can be measured by multiple collector inductively coupled plasma mass spectrometry (MC-ICP-MS) in combination with hydride generation and desolvation device. Although oceans are important targets for research, precise isotopic analysis of Se in seawater is generally difficult owing to its low concentrations and the much higher concentrations of other elements. We developed a robust, accurate method for the precise determination of Se isotopic composition in seawater. A hydride generator combined with a desolvation device with methane addition was coupled to MC-ICP-MS to measure Se isotopes precisely. Two new thiol resins were used to preconcentrate and separate Se from the seawater matrix efficiently, and Se was quickly eluted by small amounts of concentrated HNO3. No detectable Se isotope fractionation was observed during the preconcentration and separation procedure. The carbon-containing plasma increased Se sensitivity, suppressed the spectral interference signal, and improved precision by >3 times. The precisions (2sd, n=24) of Merck Se standard solutions for δ82/78Se, δ82/77Se, and δ82/76Se were 0.07‰, 0.10‰, and 0.16‰, respectively. The δ82/76Se values of standard solutions agreed well with results obtained by other research groups. The method was used to obtain a depth profile for dissolved inorganic Se (DISe) isotopes in seawater from the Northwestern Pacific Ocean. The range of δ82/76DISe was 0.41‰ to 1.59‰, indicating that Se isotopes fractionate sufficiently to clarify the biogeochemical cycling of this element in the ocean.

微量湿式分析による分子レベル同位体比の品質管理と確度向上 : 特に天然存在比の正確な評価とStable Isotope Probing(SIP)法の応用に向けて( 有機化合物の安定同位体比を用いた有機地球化学的研究の発展とその応用(Part I))

微量湿式分析による分子レベル同位体比の品質管理と確度向上 : 特に天然存在比の正確な評価とStable Isotope Probing(SIP)法の応用に向けて( 有機化合物の安定同位体比を用いた有機地球化学的研究の発展とその応用(Part I))

Optimization of on-line hydrogen stable isotope ratio measurements of halogen- and sulfur-bearing organic compounds using elemental analyzer-chromium/high-temperature conversion isotope ratio mass spectrometry (EA-Cr/HTC-IRMS).

Accurate hydrogen isotopic analysis of halogen- and sulfur-bearing organics has not been possible with traditional high-temperature conversion (HTC) because the formation of hydrogen-bearing reaction products other than molecular hydrogen (H2 ) is responsible for non-quantitative H2 yields and possible hydrogen isotopic fractionation. Our previously introduced, new chromium-based EA-Cr/HTC-IRMS (Elemental Analyzer-Chromium/High-Temperature Conversion Isotope Ratio Mass Spectrometry) technique focused primarily on nitrogen-bearing compounds. Several technical and analytical issues concerning halogen- and sulfur-bearing samples, however, remained unresolved and required further refinement of the reactor systems. The EA-Cr/HTC reactor was substantially modified for the conversion of halogen- and sulfur-bearing samples. The performance of the novel conversion setup for solid and liquid samples was monitored and optimized using a simultaneously operating dual-detection system of IRMS and ion trap MS. The method with several variants in the reactor, including the addition of manganese metal chips, was evaluated in three laboratories using EA-Cr/HTC-IRMS (on-line method) and compared with traditional uranium-reduction-based conversion combined with manual dual-inlet IRMS analysis (off-line method) in one laboratory. The modified EA-Cr/HTC reactor setup showed an overall H2 -recovery of more than 96% for all halogen- and sulfur-bearing organic compounds. All results were successfully normalized via two-point calibration with VSMOW-SLAP reference waters. Precise and accurate hydrogen isotopic analysis was achieved for a variety of organics containing F-, Cl-, Br-, I-, and S-bearing heteroelements. The robust nature of the on-line EA-Cr/HTC technique was demonstrated by a series of 196 consecutive measurements with a single reactor filling. The optimized EA-Cr/HTC reactor design can be implemented in existing analytical equipment using commercially available material and is universally applicable for both heteroelement-bearing and heteroelement-free organic-compound classes. The sensitivity and simplicity of the on-line EA-Cr/HTC-IRMS technique provide a much needed tool for routine hydrogen-isotope source tracing of organic contaminants in the environment. Copyright © 2016 John Wiley & Sons, Ltd.

Validation of GC-IRMS techniques for δ13C and δ2H CSIA of organophosphorus compounds and their potential for studying the mode of hydrolysis in the environment.

Compound-specific stable isotope analysis (CSIA) is among the most promising tools for studying the fate of organic pollutants in the environment. However, the feasibility of multidimensional CSIA was limited by the availability of a robust method for precise isotope analysis of heteroatom-bearing organic compounds. We developed a method for δ 13C and δ 2H analysis of eight organophosphorus compounds (OPs) with different chemical properties. In particular, we aimed to compare high-temperature conversion (HTC) and chromium-based HTC (Cr/HTC) units to explore the limitations of hydrogen isotope analysis of heteroatom-bearing compounds. Analysis of the amount dependency of the isotope values (linearity analysis) of OPs indicated that the formation of HCl was a significant isotope fractionation process leading to inaccurate δ 2H analysis in HTC. In the case of nonchlorinated OPs, by-product formation of HCN, H2S, or PH3 in HTC was observed but did not affect the dynamic range of reproducible isotope values above the limit of detection. No hydrogen-containing by-products were found in the Cr/HTC process by use of ion trap mass spectrometry analysis. The accuracy of gas chromatography-isotope ratio mass spectrometry was validated in comparison with elemental analyzer-isotope ratio mass spectrometry. Dual-isotope fractionation yielded Λ values of 0 ± 0 at pH 7, 7 ± 1 at pH 9, and 30 ± 6 at pH 12, indicating the potential of 2D CSIA to characterize the hydrolysis mechanisms of OPs. This is the first report on the combination of δ 2H and δ 13C isotope analysis of OPs, and this is the first study providing a systematic evaluation of HTC and Cr/HTC for hydrogen isotope analysis using OPs as target compounds. Graphical Abstract Comparison of δ2H measurement of non-chlorinated and chlorinated OPs via GC-Cr/HTC-IRMS and GC-HTC-IRMS system.

Compound-specific bromine isotope ratio analysis using gas chromatography/quadrupole mass spectrometry.

Brominated organic compounds (BOCs) are common persistent toxic pollutants. Compound-specific stable bromine isotope ratio analysis is one of the potential approaches for investigating BOC transformations in the environment. In the present study, we demonstrate that precise bromine isotope analysis of BOCs can be successfully performed by gas chromatography/quadrupole mass spectrometry (GC/qMS) systems that are widely available in analytical laboratories. Optimization and validation of the GC/qMS method were performed by analysis of bromoform, 3-bromophenol and 4-bromotoluene. In addition, comparison of the results obtained by GC/qMS and GC/multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) for 1,2-dibromoethane and 3-bromophenol samples with different bromine isotope composition was carried out to evaluate the analytical performance of the developed method. Precisions in the range 0.2-0.3‰ were attained for sample amounts in the range of tens to thousands pmol. Good correlation between the results obtained by GC/qMS and GC/MC-ICPMS for laboratory standard materials (1,2-dibromoethane and 3-bromophenol) (regression coefficient R(2) >0.98) was achieved. The GC/qMS method for bromine isotope analysis shows a good performance and can be applied routinely for studying transformations of BOCs. Due to the observed dependence of the measured isotope ratios on the amount of the analyte and the calculation scheme applied, normalization of the results versus appropriate standards is required for source attribution applications. Copyright © 2016 John Wiley & Sons, Ltd.

Preliminary Figures of Merit for Isotope Ratio Measurements: The Liquid Sampling-Atmospheric Pressure Glow Discharge Microplasma Ionization Source Coupled to an Orbitrap Mass Analyzer.

In order to meet a growing need for fieldable mass spectrometer systems for precise elemental and isotopic analyses, the liquid sampling-atmospheric pressure glow discharge (LS-APGD) has a number of very promising characteristics. One key set of attributes that await validation deals with the performance characteristics relative to isotope ratio precision and accuracy. Owing to its availability and prior experience with this research team, the initial evaluation of isotope ratio (IR) performance was performed on a Thermo Scientific Exactive Orbitrap instrument. While the mass accuracy and resolution performance for Orbitrap analyzers are well-documented, no detailed evaluations of the IR performance have been published. Efforts described here involve two variables: the inherent IR precision and accuracy delivered by the LS-APGD microplasma and the inherent IR measurement qualities of Orbitrap analyzers. Important to the IR performance, the various operating parameters of the Orbitrap sampling interface, high-energy collisional dissociation (HCD) stage, and ion injection/data acquisition have been evaluated. The IR performance for a range of other elements, including natural, depleted, and enriched uranium isotopes was determined. In all cases, the precision and accuracy are degraded when measuring low abundance (<0.1% isotope fractions). In the best case, IR precision on the order of 0.1% RSD can be achieved, with values of 1%-3% RSD observed for low-abundance species. The results suggest that the LS-APGD is a promising candidate for field deployable MS analysis and that the high resolving powers of the Orbitrap may be complemented with a here-to-fore unknown capacity to deliver high-precision IRs. Graphical Abstract ᅟ.

Selenium isotope analysis by N-TIMS: Potential and challenges

The isotope composition of selenium (Se) can provide important constraints on biological, geochemical, and cosmochemical processes taking place in different reservoirs on Earth and during planet formation. To provide precise qualitative and quantitative information on these processes, accurate and highly precise isotope data need to be obtained. The currently applied ICP-MS methods for Se isotope measurements are compromised by the necessity to perform a large number of interference corrections. Differences in these correction methods can lead to discrepancies in published Se isotope values of rock standards which are significantly higher than the acclaimed precision. An independent analytical approach applying a double spike (DS) and state-of-the-art TIMS may yield better precision due to its smaller number of interferences and could test the accuracy of data obtained by ICP-MS approaches. This study shows that the precision of Se isotope measurements performed with two different Thermo Scientific™ Triton™ Plus TIMS is distinctly deteriorated by about ±1‰ (2 s.d.) in δ80/78Se by a memory Se signal of up to several millivolts and additional minor residual mass bias which could not be corrected for with the common isotope fractionation laws. This memory Se has a variable isotope composition with a DS fraction of up to 20% and accumulates with increasing number of measurements. Thus it represents an accumulation of Se from previous Se measurements with a potential addition from a sample or machine blank. Several cleaning techniques of the MS parts were tried to decrease the memory signal, but were not sufficient to perform precise Se isotope analysis. If these serious memory problems can be overcome in the future, the precision and accuracy of Se isotope analysis with TIMS should be significantly better than those of the current ICP-MS approaches.

Molybdenum isotopic analysis by negative thermal ionization mass spectrometry (N-TIMS): effects on oxygen isotopic composition

We developed a new, highly precise, and accurate Mo isotope analysis by thermal ionization mass spectrometry in negative ionization mode (N-TIMS) by determining the in situ O isotope composition for each measurement and using the data to correct for the O isotope interferences.

On-line separation of strontium from a matrix and determination of the 87Sr/86Sr ratio by Ion Chromatography/Multicollector-ICPMS

In this work a high throughput, robust and sensitive method for the precise isotopic analysis of 87Sr/86Sr by coupling Ion Chromatography (IC) and Multicollector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) is presented.

Precise and accurate uranium isotope analysis by modified total evaporation using 1013 ohm current amplifiers

This study presents analytical advances in thermal ionization mass spectrometry for uranium isotope analysis involving minor isotopes. The potential of 1013 ohm current amplifiers for detecting minor isotope ion beams down to the 10 kcps range during modified total evaporation analyses is assessed on sub-microgram U loads, which is one order of magnitude less material than typical. Sub-‰ to ‰ precision and accuracy may be achieved for uranium isotopic ratios in the 10−5 to 10−4 range. This is 1.2–2.9 times better than expected from scaling down the performance achieved on microgram loads using 1012 ohm current amplifiers.

Plume mapping and isotopic characterisation of anthropogenic methane sources

Methane stable isotope analysis, coupled with mole fraction measurement, has been used to link isotopic signature to methane emissions from landfill sites, coal mines and gas leaks in the United Kingdom. A mobile Picarro G2301 CRDS (Cavity Ring-Down Spectroscopy) analyser was installed on a vehicle, together with an anemometer and GPS receiver, to measure atmospheric methane mole fractions and their relative location while driving at speeds up to 80 kph. In targeted areas, when the methane plume was intercepted, air samples were collected in Tedlar bags, for δ13C–CH4 isotopic analysis by CF-GC-IRMS (Continuous Flow Gas Chromatography-Isotope Ratio Mass Spectrometry). This method provides high precision isotopic values, determining δ13C–CH4 to ±0.05 per mil. The bulk signature of the methane plume into the atmosphere from the whole source area was obtained by Keeling plot analysis, and a δ13C–CH4 signature, with the relative uncertainty, allocated to each methane source investigated. Both landfill and natural gas emissions in SE England have tightly constrained isotopic signatures. The averaged δ13C–CH4 for landfill sites is −58 ± 3‰. The δ13C–CH4 signature for gas leaks is also fairly constant around −36 ± 2‰, a value characteristic of homogenised North Sea supply. In contrast, signatures for coal mines in N. England and Wales fall in a range of −51.2 ± 0.3‰ to −30.9 ± 1.4‰, but can be tightly constrained by region. The study demonstrates that CRDS-based mobile methane measurement coupled with off-line high precision isotopic analysis of plume samples is an efficient way of characterising methane sources. It shows that isotopic measurements allow type identification, and possible location of previously unknown methane sources. In modelling studies this measurement provides an independent constraint to determine the contributions of different sources to the regional methane budget and in the verification of inventory source distribution.

Lead isotopic analysis of Antarctic snow using multi-collector ICP-mass spectrometry

Precise and accurate lead isotopic analysis of Antarctic snow at the pg g−1 concentration level has been achieved by combining a total consumption sample introduction system with MC-ICP-MS.

High-precision Fe isotopic analysis of whole blood for biomedical purposes without prior isolation of the target element

Accurate and precise isotopic analysis of Fe in whole blood using multi-collector mass spectrometry is possible after acid digestion and dilution, provided that mass discrimination is corrected for using a combination of internal and external correction.

Direct detection and isotope analysis of individual particles in suspension by single particle mode MC-ICP-MS for nuclear safety

Direct detection and precise isotope analysis of individual particles in suspension by single particle mode MC-ICP-MS.