Plasma Source Mass Spectrometry Research Articles

Lead Isotopes and the Sources of Granitic Magmas: The Sveconorwegian Granite and Pegmatite Province of Southern Norway

Lead isotope analyses of K-feldspar from late Sveconorwegian (900–1000 Ma) granitic pegmatites and A-type, ferroan granitic intrusions in four different areas of southern Norway analyzed by laser-ablation inductively coupled plasma source mass spectrometry (LA-ICPMS) give compositions in the range 206Pb/204Pb = 16.637 to 17.555, 207Pb/204Pb = 15.445 to 15.534, 208Pb/204Pb = 36.317 to 37.459. These compositions broadly overlap with the initial compositions estimated from previously published solution TIMS whole-rock and feldspar Pb isotope analyses of late Sveconorwegian granitic plutons across the region, suggesting that magmas forming A-type granite plutons and granitic pegmatites have been derived from broadly similar source rocks, i.e., from a continental crust that initially formed in Palaeoproterozoic time (ca. 2.10–1.86 Ga), and subsequently underwent intracrustal partial melting, differentiation and rejuvenation via mafic underplating in Mesoproterozoic time.

Relevant aspects on biomonitoring of heavy metal concentration in environmental air in Asunción city

Introduction: Briophytes (mosses) have long been used to determine the concentration of heavy metals as an alternative to the collection of atmospheric aerosols. We elaborated the present study to evaluate the environmental concentration of lead, cadmium, mercury and arsenic in autochthonous species of moss exposed during a period to urban environment and to analyze some methodological aspects of biomonitoring in Paraguay. Material and methods: In an observational study moss samples were obtained from Cerro Patiño (34.4km from Asuncion) to be transplanted in 5 sites of high vehicular traffic in the city of Asunción. One of the samples was taken as control (Moss control 1). The samples were left outdoors for 58 days (2 September 2013 - 29 October 2013) and then collected and subjected to study using the Inductive Coupling Plasma Source Mass Spectrometry technique. The bryophytes were characterized and recorded all the climatological variables that occurred during the study period. A second sampling phase of control moss was required (Moss control 2). Results: After 58 days of exposure, lead and arsenic levels were detected.  The bryophytes used belonged to two families: hypnaceae and pilotrichaceae. The range of temperature, relative humidity, wind and precipitation did not reach extreme levels during the cycle studied. Discussion: Discrete levels of lead and arsenic are detected in the samples studied here and could represent the studied areas, although other research on variation within and between the moss species of our country is necessary.

Essential (Cu, Zn) and nonessential (Pb, Cd) metals in the muscle of leopard groupers (Mycteroperca rosacea) from a mining port in the Gulf of California, Mexico: human health risk assessment.

Mining activities are a current environmental issue due to heavy metal release and subsequent metal uptake by organisms. In this study, we quantified the concentrations of essential (Cu, Zn) and toxic (Cd, Pb) elements in the muscle of 248 leopard groupers, Mycteroperca rosacea, captured by spearfishing and free diving close to a mining district in the Gulf of California during 2014-2015. We analysed metals using high-resolution inductively coupled plasma source mass spectrometry (HR-ICP-MS). We analysed metal concentrations by fish size, sex, maturity, season, year and risk factor for human consumption. The results indicated common levels of essential elements (Cu: 11 ± 34.3μg/g, Zn: 377 ± 1390μg/g) in comparison with toxic elements (Cd: 0.06 ± 0.1μg/g, Pb: 0.98 ± 1.5μg/g). Cadmium was within the permissible limit of Mexican standards (0.5μg/g), but lead content bordered its limit (1.0μg/g). Heavy metal concentrations were comparable between males and females. Metal variations were not significantly correlated with sex, maturity, season or year (p > 0.05). The evaluation of benefits (daily mineral intake) and risks (target hazard quotients) to health indicated that these fish did not represent a risk of adverse effects to consumers within worldwide limits, while the nutritional benefits were high.

Impact of deforestation on soil iron chemistry and isotope signatures in Amazonia

We examined the consequences of soil erosion processes following deforestation and long-term pasture establishment for soil chemical and physical properties and Fe isotope compositions within two distinct areas in the Eastern and Central parts of Amazonia (near Rio Capim, Para, Brazil and Lake Balbina/Rio Uatuma, Amazonas, Brazil).For each area studied, soils selected under forest cover and pasture or after recent slash-and-burn practices were investigated. In both forest ecosystems studied, pedogenesis along slopes reflects the evolution of lateritic crust bearing soils (Ferralsol) into iron depleted soils after leaching (Acrisol) and redox processes (Gleysol). Measurements performed by plasma source mass spectrometry show a large range of iron isotope signature within the soil profiles studied at the bottom of the slopes (i.e. foot slope and/or valley soils), under both forest and pasture. Iron isotopic signature in foot slope soils under forest cover (δ57FeIRMM-14 ~ +0.2 to +0.6‰) and pasture (δ57FeIRMM-14 ~ +0.3‰) are significantly heavier than both the continental crust baseline and the reference ferralitic soils from the top of the hill (δ57FeIRMM-14 ~ +0.1‰). This enrichment in heavy isotopes is attributed to the preferential mobilisation and loss of light iron during pedogenesis that involves redox processes in areas periodically flooded at the foot slope and valley soils. Under forest, light iron depletion (where ~90% of the iron was leached in the first metre of the soil) has greater influence on the soil isotopes signature, particularly in foot slope sand-rich soils close to the river system with a remaining Fe having δ57Fe IRMM-14 ~ +0.6‰. Under pasture where soils experienced erosion processes, iron depletion in foot slope and riverside soils is less important (where only a little more than half of the iron was leached in the first metre of the soil) and the resulting δ57FeIRMM-14 ~ +0.4‰ suggests an input of light iron isotopes via colluvic material deposition. This difference indicates that geomorphological changes due to erosion processes following deforestation (i.e. colluvic processes) lead to an “isotopic rejuvenation” of the soils in the valley, mostly apparent within the riverside soils.For comparison, we investigated isotopic changes in a recently deforested small watershed, near Lake Balbina, Central Amazonia, focusing on riverside soils. Results confirm that the isotopic rejuvenation effect appears within a few months following the first stage of deforestation as a consequence of erosion processes following slash-and-burn practices. Erosion can remove isotopically lighter (i.e. close to the continental crust value of ~0.1‰ in δ57Fe) iron bearing soil material from the top of the hill. When such colluvial soil material accumulates in the bottom of the hills on soils that were initially depleted in light iron isotopes, again due to podzolisation as described in the previous site, it induces an “isotopic rejuvenation” (tending again towards a lighter, continental crust-like δ57Fe signature) of the foot slope and riverside soils, besides changes in landscape morphology, water drainage and soil functioning (i.e. hydromorphic processes). Hence, this study illustrates that Fe isotopes can be used to identify erosion within a deforestation context through “isotope rejuvenation”, even when soil textures make it challenging to unravel.

A comparison of sulfur isotope measurements of geologic materials by inductively coupled plasma and gas source mass spectrometry

Sulfur isotope measurements by multi collector-inductively coupled plasma-mass spectrometry (MC-ICP-MS) require up to one hundred times less sulfur than traditional measurements via elemental analyzer isotope ratio mass spectrometry (EA-IRMS). Here, we report an improved MC-ICP-MS protocol for measuring δ34S values in different natural samples, specifically, calcium-sulfate minerals, carbonate associated sulfate, and dissolved sulfate in water. Sample preparation and subsequent anion exchange chromatography quantitatively recovers sulfur as sulfate. However, for samples with high and complex anion budgets, such as meteoric water, a stronger retention of sulfate on the anion exchange resin is observed relative to samples that contain sulfur as pure sulfate such as calcium-sulfate minerals and carbonate associated sulfate. An extended elution scheme with HNO3 is therefore required to achieve full recovery of sulfur, and thus accurate and reproducible δ34S values for the different materials investigated. Sulfur isotope measurements were performed on a Neptune Plus MC-ICP-MS coupled to an Apex-Ω desolvator, resulting in a “dry” plasma, negligible level of isobaric interferences, a sensitivity of >40 V ppm−1 sulfur, and a precision of 0.2‰ (2 S.D.) for δ34S for as little as 70 ng sulfur of a pure sulfate solution. The accuracy of the procedure was tested against duplicate δ34S EA-IRMS measurements for eleven different geologic samples. The EA-IRMS and MC-ICPMS values generally agree well within analytical uncertainty. However, procedural blank levels are on the order of a few tens of nanogram sulfur, and are thus the main limiting factor for accurate low-level sulfur isotope measurements with MC-ICP-MS.

Femtosecond laser ablation inductively coupled plasma source mass spectrometry for elemental and isotopic analysis: are ultrafast lasers worthwhile?

The figures of merit of fs laser ablation for LA-ICP-MS analysis are reviewed.

Plasma source mass spectrometry for radioactive waste characterisation in support of nuclear decommissioning: a review

The efficient characterization of nuclear waste materials represents a significant challenge during nuclear site decommissioning, with a range of radionuclides requiring measurement in varied and often complex sample matrices. ICP-MS is increasingly a practicable alternative to radiometric methods for medium to long-lived radionuclides.

A review on the mass spectrometric studies of americium: Present status and future perspective.

The manuscript reviews the various mass spectrometric techniques for analysis and chemical studies of Americium. These methods include thermal ionization mass spectrometry (TIMS), and inductively coupled plasma source mass spectrometry (ICPMS) for the determination of Am isotope ratios and concentration in nuclear fuel samples of interest in nuclear technology, and in complex biological and environmental samples. Ultra-sensitive mass spectrometric techniques of resonance-ionization mass spectrometry (RIMS), and accelerator-based mass spectrometry (AMS) are also discussed. The novel applications of electrospray ionization mass spectrometry (ESIMS) to understand the solution chemistry of Am and other actinides are presented. These studies are important in view of the world-wide efforts to develop novel complexing agents to separate lanthanides and minor actinides (Am, Np, and Cm) for partitioning and transmutation of minor actinides from the point of view of nuclear waste management. These mass spectrometry experiments are also of great interest to examine the covalent character of actinides with increasing atomic number. Studies on gas-phase chemistry of Am and its oxides with Knudsen effusion mass spectrometry (KEMS), Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS), and laser-based experiments with reflectron time-of-flight mass spectrometer (R-ToF) are highlighted. These studies are important to understand the fundamental chemistry of 5f electrons in actinides. Requirement of certified isotopic reference materials of Am to improve the accuracy of experimental nuclear data (e.g., the half-life of 243 Am) is emphasized. © 2016 Wiley Periodicals, Inc. Mass Spec Rev.

Determination of Rare- Earth Elements in White Marbles by Inductively Coupled Plasma Source Mass Spectrometry

Determination of Rare- Earth Elements in White Marbles by Inductively Coupled Plasma Source Mass Spectrometry Nurhayat Özdemir, Şeref Güçer Abstract Marmara (23), Afyon (31), Uşak (17) and Paros(9) white marble samples were analyzed by ICP-MS for the quantitative determination of rare earth element (REE) concentration The levels of the isotopes of rare earth elements 139La, 140Ce, 141Pr, 146Nd, 147Sm, 151Eu, 157Gd, 159Tb, 163Dy, 165Ho, 167Er, 169Tm, 173Yb and 175Lu Full Text: PDF DOI: 10.15640/jcb.v4n2a3

Determination of Boron Isotope Ratios in Tooth Enamel by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) After Matrix Separation by Ion Exchange Chromatography

Boron isotopes in teeth has been a new proxy for dietary reconstructions and its resistance to diagenetic alteration. In this study a method using inductively coupled plasma source mass spectrometry (ICP-MS) for the measurement of boron isotope ratio in human dental enamel has been developed. Human dental enamel were digested with HNO3-H2O2 in a microwave system. Boron in solution was separated from the matrix components using Amberlite IRA-743 resin. The factors that may affect precision and accuracy in isotope ratio determination by ICP-MS, including memory effects, mass bias drift, and concentration effects, were investigated to obtain optimum conditions. Then, the 10B/11B ratios in teeth were measured. The results showed that 2% of HNO3 + 2% of NH3•H2O, selected as the diluent/rinse solution could be effective in the elimination of boron memory effect. There was no concentration effect on boron isotope ratios when the ratio of samples B concentration to standard B concentration (refers to Csample/Cstd) varied from 0.5 to 2. The result of 10B/11B ratios in tooth enamel by sex and age fluctuated over a broad range, ranged from 0.2007 to 0.2574. This method is expected to be used for boron isotope ratio analyses in archeometry, forensic identification, paleoecology, and other disciplines in the future.

High-precision measurements of seawater Pb isotope compositions by double spike thermal ionization mass spectrometry

A new method for the determination of seawater Pb isotope compositions and concentrations was developed, which combines and optimizes previously published protocols for the separation and isotopic analysis of this element. For isotopic analysis, the procedure involves initial separation of Pb from 1 to 2L of seawater by co-precipitation with Mg hydroxide and further purification by a two stage anion exchange procedure. The Pb isotope measurements are subsequently carried out by thermal ionization mass spectrometry using a 207Pb–204Pb double spike for correction of instrumental mass fractionation. These methods are associated with a total procedural Pb blank of 28±21pg (1sd) and typical Pb recoveries of 40–60%. The Pb concentrations are determined by isotope dilution (ID) on 50mL of seawater, using a simplified version of above methods. Analyses of multiple aliquots of six seawater samples yield a reproducibility of about ±1 to ±10% (1sd) for Pb concentrations of between 7 and 50pmol/kg, where precision was primarily limited by the uncertainty of the blank correction (12±4pg; 1sd). For the Pb isotope analyses, typical reproducibilities (±2sd) of 700–1500ppm and 1000–2000ppm were achieved for 207Pb/206Pb, 208Pb/206Pb and 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, respectively. These results are superior to literature data that were obtained using plasma source mass spectrometry and they are at least a factor of five more precise for ratios involving the minor 204Pb isotope. Both Pb concentration and isotope data, furthermore, show good agreement with published results for two seawater intercomparison samples of the GEOTRACES program. Finally, the new methods were applied to a seawater depth profile from the eastern South Atlantic. Both Pb contents and isotope compositions display a smooth evolution with depth, and no obvious outliers. Compared to previous Pb isotope data for seawater, the 206Pb/204Pb ratios are well correlated with 207Pb/206Pb, underlining the significant improvement achieved in the measurement of the minor 204Pb isotope.

Lu-Hf 동위원소시스템의 지질학적 활용

The Lu-Hf isotope system, coupled with the advent of multiple collector inductively coupled plasma source mass spectrometry, is now widely utilized as a tracer for geological processes. The paper presents a comprehensive review on the principles of the Lu-Hf isotopes, and its current and potential applications to both geochronology and petrogenesis. Finally, based on the Lu-Hf isotopic data from Korean mafic and ultramafic rocks, its has been discussed evolution of the mantle beneath the Korean Peninsula.

Ultra-precise titanium stable isotope measurements by double-spike high resolution MC-ICP-MS

In this contribution, we present a new technique for the ultra-precise determination of titanium stable isotope composition (expressed as δ49Ti or deviation of the 49Ti/47Ti ratio to the reference standard) of geological samples by multi-collection plasma source mass spectrometry (MC-ICPMS) using the double spike method to correct for instrumental mass bias. Tails of polyatomic spectral interferences on 46Ti are accounted for by using sample-standard bracketing in high-resolution mode. Choice of ideal double and triple spike composition is investigated and results show that analytical error for a single measurement is optimised for a 47Ti–49Ti double spike composed of ca. 50% of each spike and mixed with ca. 52% of sample. Measurements of pure Ti solution show that internal error on single measurements of ca. 0.010‰ (95% c.i.) is attainable on δ49Ti, in agreement with the error model. Due to the lack of a widely available reference isotopic standard for titanium, all results are expressed as deviations relative to newly created reference material (OL-Ti standing for Origins Laboratory – titanium) prepared from an ultra-pure titanium metal rod. A range of analytical tests demonstrates the robustness of our method. An external reproducibility of ca. 0.020‰ (2sd) is routinely achievable for Ti stable isotopes. Data for a range of basaltic rock standards as well as a subduction zone basalt reference suite is presented and show that the Ti stable isotope compositions of terrestrial basalt show resolvable variations but are overall very close to the OL-Ti reference standard. The average Ti isotopic composition of the basalts studied here is the present best estimate of the upper mantle composition; δ49Ti = +0.004 ± 0.062‰ (2sd).

Silicon isotope variations in the inner solar system: Implications for planetary formation, differentiation and composition

Accurate and precise Si isotope measurements were obtained using magnesium doping and high-resolution plasma source mass spectrometry for samples representative of the Earth, as well as lunar samples, meteorites from Mars (SNC), eucrites, a howardite, carbonaceous chondrites (CC), ordinary chondrites (OC) and enstatite chondrites (EC). Our data confirm that significant Si isotope fractionations exist among the inner solar system planetary bodies. They show that the Earth and the Moon share the same Si isotopic composition, which is heavier than all other measured bodies, in agreement with most of previous studies. At the other end of the spectrum, enstatite chondrites have the lightest Si isotope compositions. In order to precisely estimate the amount of Si that may have entered the Earth’s core, we developed a refined model of Si partitioning based on continuous planetary accretion that takes into account the likely variations in T, P and fO2 during the Earth’s accretion, as well as isotopic constraints involving metal–silicate partitioning derived from both experimental and natural sample data sets.Assuming that the difference between the isotopic signature of the bulk silicate Earth (BSE) and chondrites solely results from Si isotope fractionation during core formation, our model implies that at least ∼12wt% Si has entered the Earth’s core, which is greater than most of the estimates based on physical constraints on core density or geochemical mass balance calculations.This result leads us to propose two hypotheses to explain this apparent contradiction: (1) At least part of the Earth’s building blocks had a Si isotope composition heavier than that observed in chondrites (i.e., δ30Si>−0.39‰). (2) If on the contrary the Earth accreted only from material having chondritic δ30Si, then an additional process besides mantle–core differentiation is required to generate a stronger isotope fractionation and lead to the observed heavy isotope composition of the bulk silicate Earth. It may be the loss of light Si isotopes during partial planetary vaporization in the aftermath of the Moon-forming giant impact. This process, which may have affected metallic cores, required a thorough isotopic re-equilibration between core and silicate to explain the similar heavy isotope composition of the silicate portions of the Earth and the Moon.

Characterization of l-cysteine capped CdTe quantum dots and application to test Cu(II) deficiency in biological samples from critically ill patients

The catalytic activity of copper ion gives, from the physiological point of view, a central role in many biological processes. Variations in the composition and location of cellular copper have been addressed given their physiological and pathological consequences. In this paper l-cysteine capped CdTe quantum dots is used for the fluorimetric determination of Cu(II) in biological samples from healthy individuals and patients admitted to the Intensive Care Units (ICU). An acceptable homogeneity in the CdTe QDs size has been obtained with an average value of 3nm. No significant alterations in the spectral properties were observed for 2 months when stored in vacutainers at 6°C and a concentration of approximately 2μM. Data from oxidative stress markers such superoxide dismutase, total antioxidant capacity and DNA damage can be correlated with a Cu(II) deficiency for the ICU patients as measured by flame-atomic absorption spectroscopy (FAAS) and inductively coupled plasma source mass spectrometry (ICP-MS). Aqueous solutions 0.3μM of l-cysteine capped CdTe QDs in MOPS buffer (6mM, pH 7.4) used at 21°C in the range 15–60min after preparation of the sample for the measurements of fluorescence gives contents in Cu(II) for erythrocytes in good agreement with those obtained in FAAS and ICP-MS but the comparative ease of use makes the fluorimetric technique more suitable than the other two techniques for routine analysis.

The Determination of Arsenic Compounds: A Critical Review

A large number of publications describe the determination of arsenic in “environmental” samples in the broadest sense, a substantial subset of which focus on plant-based foodstuffs. There is a considerable interest in the inorganic arsenic content of food, especially rice, as there is recent evidence that concentrations may be high enough to exceed acceptable risk thresholds. The methodology for the determination of arsenic in rice is critically evaluated and results (a) for a rice flour reference material (National Institute of Standards SRM 1568a, certified only for total arsenic) and (b) a recent proficiency test (run by the European Commission's Joint Research Centre Institute for Reference Materials and Measurement) are examined. Difficulties with this particular analysis may lie in the sample preparation stages, over which there is still disagreement with regard to species stability, though a simple, hot-water extraction may be sufficient. High performance liquid chromatography separations with plasma-source mass spectrometry detection are popular; however, chromatographic separations are often not adequately described, the enhancement effect of carbon-containing species is often overlooked, and the fate of chlorine-containing species, responsible for an isobaric overlap interference, often obscure. Compound-dependent responses, for which there is a plenty of evidence, are almost never acknowledged or discussed.

A Simple and Fast Separation Method of Fe Employing Extraction Resin for Isotope Ratio Determination by Multicollector ICP-MS

A new, simple and fast separation method for Fe using an extraction chromatographic resin, Aliquat 336 (commercially available as TEVA resin) has been developed. A one milliliter column containing 0.33 mL TEVA resin on 0.67 mL CG-71C was used.Iron was adsorbed with 6mol·L-1 HCl + H2O2 on TEVA resin, and recovered with 2 mol·L-1HNO3. The recovery yield and total blank were 93.5 ± 6.5% and 6 ng, respectively. Theseparation method is simple, and takes < 2 hours. For evaluation of the Fe separation, Fe isotope ratios were measured by a double-spike method employing multicollector inductively coupled plasma source mass spectrometry (MC-ICP-MS) with repeatability of 0.06‰ (SD) for the standard solution and ~0.05‰ for the silicate samples. Therefore, the column chemistry developed in this study is a viable option for Fe isotope ratio measurement by MC-ICP-MS.

Comparison of novel and conventional calibration techniques for the analysis of urine samples using plasma source mass spectrometry combined with a new dual-drop-on-demand aerosol generator

The accuracy and precision of the analytical data from the analysis of liquid samples with high matrix load often suffer from a compromised performance of the sample introduction system. This is especially significant in the case of miniaturized, pneumatic low flow nebulizers. Alternative low-flow sampling devices based on different operating principles are imperative to overcome this drawback. The superior performance of such an alternative liquid sample introduction system for ICP-MS, the drop-on-demand (DOD) aerosol generator based on thermal inkjet technology, was recently outlined by the same group for the analysis of aqueous standard solutions. Current improvements of the system now allow for the independent operation of two sampling nozzles, which expands the system capabilities to independently dosing two liquids simultaneously into the carrier gas stream of an ICP-MS. The applicability of the proposed dual-DOD (dDOD) ICP-MS method to the analysis of real urine samples is outlined. Its susceptibility to matrix effects was studied through 2-dimensional ion distributions within the ICP for different matrices. A new calibration strategy for ICP-MS based on the dosing frequencies of the dDOD (dosing frequency-based calibration, DFC) and its application to trace metal analysis in micro-volumes of real samples with high matrix content are presented. Using this method Li, Sr, Mo, Sb and Cs were accurately determined in the concentration range of 8–122 μg L−1 in urine reference material. The advantages of the DFC, e.g. minimum sample and analysis time consumption, are outlined and the quality of the achievable results with respect to accuracy and precision is critically discussed. All analytical data are compared to those obtained with a conventional MicroMist nebulization system in combination with ICP-MS using classic calibration procedures.

Studies of SRM NIST glasses by laser ablation multicollector inductively coupled plasma source mass spectrometry (LA-ICP-MS)

In this paper we present the fundamentals for a protocol for optimizing isotopic determination of lead for comparison of man-made glass by use of laser ablation inductively coupled mass spectrometry (LA-ICP-MS). Comparison of objects in order to establish a possible common origin is relevant within different disciplines, such as forensic sciences and archaeometry. Measurement of isotope ratios (IR) of lead is a method widely used by geochemists in order to establish the origin and evolution of minerals and rocks. In archaeometry, lead isotopes are used to determine the provenance of artefacts. Lead isotope ratios have shown potential not only for provenance determination, but also for comparison of different objects. Laser ablation as a sample introduction method to inductively coupled plasma mass spectrometry (LA-ICP-MS) is an established method in the geosciences, where it is used both for concentration and isotope ratio analysis of solids, but has still not obtained the same position in forensic science and archaeometry. The elegance of laser ablation as a sample introduction system is due to the simplicity of sample preparation and high spatial resolution. This spatial resolution provides advantages over methods where the sample has to be dissolved or melted in larger amounts. In order to outline a suitable protocol for analysis of lead isotope ratios in glass by LA-ICP-MS, we have followed a threefold approach. Firstly, we describe the influence of laser conditions on the Pb-isotope ratios obtained for low-lead glasses such as SRM NIST 610–614. Secondly, we evaluate the influence of the selection of detectors (ion counters vs. Faraday detectors) on the reliability of the final result. Thirdly, we discuss the phenomenon of fractionation and instrumental mass discrimination for lead during analysis.

Calcium isotope measurement by combined HR-MC-ICPMS and TIMS

We report a novel approach for the chemical purification of Ca from silicate rocks by ion-exchange chromatography, and a highly-precise method for the isotopic analysis of Ca—including the smallest isotope 46Ca (0.003%)—by high-resolution multiple collector inductively coupled plasma source mass spectrometry (HR-MC-ICPMS), in combination with thermal ionization mass spectrometry (TIMS). Using this approach, we measured the Ca isotope composition of a number of terrestrial rock standards and seawater. Based on these data, we show that the non-mass-dependent abundances of μ43Ca, μ46Ca, and μ48Ca (normalized to 42Ca/44Ca) can be measured with an external reproducibility of 1.8, 45 and 12.5 ppm, respectively, when measured by HR-MC-ICPMS and μ40Ca and μ43Ca to 80 and 23 ppm, respectively, when measured by TIMS (μ notation is the per 106 deviation from the reference material). Comparison with earlier studies demonstrate that it is possible to measure the mass-dependent Ca isotope composition of terrestrial materials using HR-MC-ICPMS with an external reproducibility comparable to that typically obtained with double spike TIMS techniques. The resolution of the mass-independent 43Ca, 46Ca and 48Ca data obtained by HR-MC-ICPMS represents more than a 45-, 120-, and 18-fold improvement, respectively, relative to earlier measurements obtained by TIMS. This improvement allows for a better understanding of the mass fractionation laws responsible for the mass-dependent fractionation of Ca present in natural samples and synthetic standards. For example, the presence of an apparent excess of ∼60 ppm in the μ48Ca composition of the SRM 915a suggests that equilibrium fractionation processes have generated the mass-dependent fractionation of this material. In contrast, the absence of residual anomalies in the mass-independent composition of seawater implies that biogenic and inorganic processes of carbonate formation fractionate Ca kinetically from seawater. Finally, we note that SRM 915b has a mass-dependent and mass-independent Ca isotope composition that is within the resolution of our method identical to that of bulk silicate Earth (BSE). This observation, together with the potential heterogeneity in the 40Ca composition of the SRM 915a inferred from our measurements, suggests that the SRM 915b is a better reference material to study the Ca isotope composition of terrestrial and non-terrestrial materials.