Multicollector Inductively Coupled Mass Spectrometry Research Articles

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

This study presents an analytical procedure for measuring the 87Sr/86Sr isotopic ratio in olive oil and pomace using multicollector-inductively coupled mass spectrometry (MC-ICPMS). The developed method combines liquid-liquid extraction with an acid solution and degradation of organic residues in the extract by dry ashing and oxidation by H2O2 and HNO3. The method enabled 87Sr/86Sr ratios to be obtained in olive oil with Sr content as low as 0.2 ng g−1, with a precision of 54 ppm. The method’s validity was confirmed by an interlaboratory comparison using NIST SRM 2387, providing the first data on its elemental Sr (2380 ± 230 ng g−1; n = 10), and 87Sr/86Sr isotopic composition (0.70908 ± 0.00004; n = 14). The procedure was applied to olive oil and pomace samples, showing that they have an identical 87Sr/86Sr ratio, which was consistent with that determined in soils from the same orchards. The results thus revealed that Sr isotopic ratios of olive oil and pomace can both be used in geographical traceability studies of olive oil, which means that, instead of processing large volume of oil, characteristic 87Sr/86Sr signatures of olive oil can be more easily obtained by analyzing small quantities of pomace obtained by centrifuging the oil.

Geochemistry, Monazite U–Pb Dating, and Li–Nd Isotopes of the Madi Rare Metal Granite in the Northeastern Part of the North China Craton

The Madi rare metal granite is a complex massif, which contains a variety of rare metals, such as Nb, Ta, Li, and Be. In this paper, the geochemical characteristics of the granite were obtained by multi‐collector inductively coupled mass spectrometry (MC‐ICP‐MS). The precise crystalline age of the granite was obtained from monazite U‐Pb dating, and the source of the granite was determined using Li‐Nd isotopes. The Madi rare metal granite is a high‐K (calc‐alkaline), peraluminous, S‐type granite. The U‐Pb monazite age indicates that the crystalline age of the granite is 175.6 Ma, which is Early Jurassic. The granite is characterized by a relatively wide range of δ7Li values (+2.99‰ to +5.83‰) and high lithium concentrations (181 ppm to 1022 ppm). The lithium isotopic composition of the granite does not significantly correlate with the degree of magmatic differentiation. An insignificant amount of lithium isotope fractionation occurred during the granitic differentiation. The lithium isotopic composition of the granite significantly differs from that of the wall rock, but it is very similar to that of a primitive mantle peridotite xenolith (mean δ7Li value +3.5‰). The plot of Li concentration versus δ7Li indicates that the Li isotopic composition of the granite is similar to that of island arc lavas. Based on the above‐described evidence, the granite was mainly derived from the crust, but it was contaminated by a deep granitic magma.

Boron isotope-based seasonal paleo-pH reconstruction for the Southeast Atlantic – A multispecies approach using habitat preference of planktonic foraminifera

The boron isotopic composition of planktonic foraminiferal shell calcite (δ11BCc) provides valuable information on the pH of ambient water at the time of calcification. Hence, δ11BCc of fossil surface-dwelling planktonic foraminifera can be used to reconstruct ancient aqueous pCO2 if information on a second carbonate system parameter, temperature and salinity is available. However, pH and pCO2 of surface waters may vary seasonally, largely due to changes in temperature, DIC, and alkalinity. As also the shell fluxes of planktonic foraminifera show species-specific seasonal patterns that are linked to intra-annual changes in temperature, it is obvious that δ11BCc of a certain species reflects the pH and thus pCO2 biased towards a specific time period within a year. This is important to consider for the interpretation of fossil δ11BCc records that may mirror seasonal pH signals. Here we present new Multi-Collector Inductively Coupled Mass Spectrometry (MC-ICPMS) δ11BCc coretop data for the planktonic foraminifera species Globigerina bulloides, Globigerinoides ruber, Trilobatus sacculifer and Orbulina universa and compare them with δ11Bborate derived from seasonally resolved carbonate system parameters. We show that the inferred season-adjusted δ11BCc/δ11Bborate relationships are similar to existing calibrations and can be combined with published δ11BCc field and culture data to augment paleo-pH calibrations. To test the applicability of these calibrations, we used a core drilled on the Walvis Ridge in the Southeast Atlantic spanning the last 330,000 years to reconstruct changes in surface-water pCO2. The reconstruction based on G. bulloides, which reflects the austral spring season, was shown to yield values that closely resemble the Vostok ice-core data indicating that surface-water pCO2 was close to equilibrium with the atmosphere during the cooler spring season. In contrast, pCO2 estimated from δ11BCc of O. universa, T. sacculifer and G. ruber that predominantly lived during the warmer seasons, exhibits up to ∼50 ppmv higher values than the Vostok ice-core data. This is probably due to the higher austral summer and fall temperatures, as shown by Mg/Ca to be on average ∼4 °C higher than during the cooler spring season, accounting for an increase in pCO2 of ∼4% per 1 °C. Our results demonstrate that paleo-pH estimates based on δ11BCc contain a significant seasonal signal reflecting the habitat preference of the recording foraminifera species.

Single laboratory comparison of MC-ICP-MS and N-TIMS boron isotope analyses in marine carbonates

Measurements of boron isotopes (δ11B) in marine carbonates are an important tool for reconstructing past ocean acidity and atmospheric carbon dioxide levels, but are challenging to obtain due to low boron concentrations and the presence of only two stable boron isotopes. Previous studies have observed differences in absolute δ11B values of marine carbonates measured via negative thermal ionization mass spectrometry (N-TIMS) and multicollector inductively coupled mass spectrometry (MC-ICP-MS) that are relatively large compared to magnitudes of δ11B variability in paleoceanographic studies. Here we investigate the cause of these δ11B offsets and implications for paleo-pH reconstructions by performing N-TIMS and MC-ICP-MS measurements within the same laboratory on a suite of eighteen homogenized samples, including inorganic calcites grown under controlled pH conditions and Quaternary planktic foraminifera. Results show that δ11B values between both measurement techniques are highly correlated (R2>0.99), but calcite δ11B values are ~0.5 to 2.7‰ lower when measured by MC-ICP-MS compared to N-TIMS. The δ11B offset between techniques cannot be attributed to procedural blank contribution, but the magnitude of offset moderately correlates with indicators of sample chemical composition, including B/Ca, Mg/Ca and δ18O (R2=0.39 to 0.50). N-TIMS δ11B does not change with calcium addition to a biogenic carbonate sample, suggesting that varying calcium abundance between samples and standards is not the reason for N-TIMS “matrix effects”. Correlation between δ18O and the δ11B offset is particularly apparent for calcites (R2=0.71); the origin of this relationship is not clear, but is not likely due to 17O interference. Although identifying the origin of measurement offsets requires further study, we demonstrate that such offsets do not affect the validity of δ11B data: The sensitivity of δ11B in inorganic calcite to pH is the same when measured by either technique, and paleo-pH reconstructed from δ11B measurements in planktic foraminifera is equivalent within uncertainty when a technique-specific constant offset is applied. Our results strongly indicate that δ11B measurements from both measurement techniques (N-TIMS and MC-ICP-MS) can be employed for paleo-pH reconstructions with equal confidence.

A new boron isotope-pH calibration for Orbulina universa, with implications for understanding and accounting for ‘vital effects’

Boron isotope ratios, as measured in planktic foraminifera, can be a useful tracer of past ocean pH, and hence help to discern the concentration of CO2 in the ancient atmosphere. However, different species of planktic foraminifera demonstrate different patterns of boron isotope variation with ambient seawater pH. Therefore when applying the proxy to questions in the geological past, species-specific calibrations are preferable. Beyond the evolutionary history of a calibrated species, we must rely on our understanding of the causes of the observed “vital effects” in the modern ocean, and the applicability of that understanding to extinct species. Here we present a new open-ocean calibration of the planktic foraminifera Orbulina universa, measured via Multi-Collector Inductively Coupled Mass Spectrometry (MC-ICPMS). Unlike other symbiont-bearing foraminifera, O. universa record a δ11B (and hence pH) that is lower than its surrounding seawater, but with a pH-sensitivity roughly equal to that of aqueous borate ion. We discuss the significance of this for application of the boron isotope proxy in deep time, with recommendations for best practice and future research directions.

A method for determining the isotopic composition of dissolved zinc in seawater by MC-ICP-MS with a 67Zn–68Zn double spike

The biogeochemical cycling of dissolved zinc in seawater is dominated by biological uptake in the surface ocean and its regeneration at depth leading to a large concentration gradient between the surface and deep ocean. The advent of multi-collector inductively coupled mass spectrometry (MC-ICP-MS) provides the marine community with a new way of probing the biogeochemical zinc cycle through changes in its isotope composition. In this paper we document the mathematical and analytical procedures involved in determining the dissolved zinc isotopic composition of seawater using the double spike technique. Seawater samples were spiked with a 67Zn–68Zn double spike, before processing. Measurement of zinc by the MC-ICP-MS requires the sample to be free of the seawater matrix and other interfering elements; for this purpose Toyopearl AF-Chelate 650M and AG1X8 resins were used to pre-concentrate zinc from seawater and separate it from major cations and anions. The optimum pH range for loading zinc for affinity chromatography was between 5 and 8. After pre-concentration, zinc was purified from other trace element by anion exchange chromatography. The reproducibility of the procedure was excellent for a deep water sample [6.55±0.34nmolL−1 and 0.59±0.02‰ (n=9) w.r.t. JMC-Lyon] and a shallow water sample [0.05±0.01nmolL−1 and 0.08±0.02‰ (n=3). w.r.t. JMC-Lyon] analyzed over a period of 1year. Analysis of GEOTRACES IC1 BATS and SAFe inter-calibration samples produced data in good agreement with data published by other groups. As a further test of the methodology, we determined the isotopic composition of dissolved zinc for samples collected at various depths from station 40°S, 162°E located in the Tasman Sea, SW Pacific Ocean. The δ66Zn vs. depth profile showed isotope variability in the upper water column (0–200m) with values ranging between −0.03‰ and 0.53‰. These variations were attributed to biological activity. In deep waters the isotope composition of dissolved zinc (0.50±0.10‰) is comparable to other data published.

Strontium isotopes and the long-term residency of thalattosuchians in the freshwater environment

AbstractThalattosuchians are crocodylomorphs mainly known from marine strata of Early Jurassic to Early Cretaceous age. They represent the earliest crocodylomorph radiation to an aquatic habitat and their evolutionary history offers very few records from freshwater settings. Here, we report several exquisitely preserved thalattosuchian skulls attributed to a derived teleosaurid from a pedogenic horizon located at the base of a fluvial series of alternating silts and sandstones of the Phu Kradung Formation (Upper Jurassic) of northeastern Thailand. Using laser ablation multicollector inductively coupled mass spectrometry (MC-ICP-MS) on tooth enamel and dentine, we measured isotopic ratios of strontium (87Sr/86Sr) to test the habitat of these teleosaurids. In addition, Sr concentrations of the dental tissues were estimated from the calibrated signal intensities of the Sr isotope measurements. The dataset includes bioapatite (teeth or scales) of eight terrestrial and five aquatic vertebrates. Theropods exhibit lower Sr concentrations both in enamel and dentine compared to others groups, a pattern in accordance with the calcium biopurification process, which predicts that Sr concentrations in the body of vertebrates decrease up the trophic chain. It also excludes the possibility that diagenesis has completely overprinted the Sr isotope compositions of the fossil assemblage, which exhibits a homogeneous87Sr/86Sr signature above the Late Jurassic seawater value. Values for teleosaurid teeth are in the range of other values for vertebrates in the continental assemblage and imply that these crocodylomorphs did not migrate between freshwater and marine habitats at least in the time constraint of the mineralizing tooth. This result represents the first demonstration that a population of teleosaurids was established for a prolonged time in a freshwater environment. Whether the ability of teleosaurids to inhabit freshwater habitats is a secondary adaptation or whether it is plesiomorphic and inherited from freshwater ancestors is discussed.

Validation of Bulk Analysis with Simulated Swipe Samples Containing Ultra-Trace Amounts of Uranium and Plutonium Using MC-ICP-MS

Suitable analytical procedures for the bulk analysis of ultra-trace amounts of uranium and plutonium have been developed using multi-collector inductively coupled mass spectrometry (MC.ICP.MS). The quantification and determination of the isotopic ratios of uranium and plutonium in three simulated swipe samples, a swipe blank, and a process blank were performed to validate the analytical performance. The analytical results for the simulated swipe samples were in good agreement with the certified values, based on the measurement quality goals for the analysis of bulk environmental samples recommended by the International Atomic Energy Agency (IAEA)

A ‘Geo-Pedo-Fingerprint’ (GPF) as a tracer to detect univocal parent material-to-wine production chain in high quality vineyard districts, Campi Flegrei (Southern Italy)

An interdisciplinary study, involving geologists, chemists and pedologists, started aiming at identifying a “Geo-Pedo-Fingerprint” (GPF) univocally linking the wine to its origin, namely, the Piedirosso vineyards growing in the Campi Flegrei volcanic area. The focal point of this research was the characterization of the whole parent material–soil–vineyard–wine system, achieved by correlating the elemental pattern – with special reference to micro-nutrients and Rare Earth Elements (REEs) – and Sr isotopic ratios, to identify a reliable and convenient ‘GPF‘, as a guaranteed indicator of wine provenance. A representative soil/Piedirosso vineyard system was identified and characterized. Samples from each soil horizon as well as from vine branches, leaves, grapes and wine were collected and analyzed. All samples were analyzed by multi-collector inductively coupled mass spectrometry (MC-ICPMS) to determine their 87Sr/86Sr isotopic composition, by ICP-Quadrupole MS to measure multi-elemental composition including REE, and by X-Ray Powder Diffraction (XRPD) for the quantitative evaluation of the mineral phases occurring in soil samples.Statistical analysis (Hierarchical Cluster Analysis, Factor Analysis) revealed the existence of separate correlations of element distribution between: i) soil, as nutrient pool source, and vegetative compartments, i.e. branches and leaves, as biochemical yards for nutrient elaboration and marshaling, ii) vegetative compartments and the productive compartment, i.e. grapes as the metabolic outcome of the vine, and, iii) the productive compartment and its artifact produced by man, i.e. wine. However, no sequential correlation of elements from soil to wine did appear, likely because clusters of elements were discriminated due to the varying takeup and fractionation processes in plants, as well as during vinification processes. Therefore, none of the investigated elements was a liable ‘GPF’ as a candidate tracer from soil to wine.In contrast, the use of a petrogenetic tracer such as 87Sr/86Sr isotopic composition provided satisfactory responses. In fact, the values of such a ratio within the entire studied chain vary in a very small range from 0.7076 to 0.7084, thus falling within the typical range for volcanites of Campi Flegrei (0.7065–0.7086). These results currently represent the only study focusing on a geotracer, such as the 87Sr/86Sr isotopic ratio, linked with a pedological survey to identify the volcanic Campanian wine-producing chains from soil parent material-to-wine.

Iron uptake and ferrokinetics in healthy male subjects of an iron-based oral phosphate binder (SBR759) labeled with the stable isotope (58)Fe.

SBR759 is a novel polynuclear iron(III) oxide-hydroxide starch·sucrose·carbonate complex being developed for oral use in chronic kidney disease (CKD) patients with hyperphosphatemia on hemodialysis. SBR759 binds inorganic phosphate released by food uptake and digestion in the gastro-intestinal tract increasing the fecal excretion of phosphate with concomitant reduction of serum phosphate concentrations. Considering the high content of ∼20% w/w covalently bound iron in SBR759 and expected chronic administration to patients, absorption of small amounts of iron released from the drug substance could result in potential iron overload and toxicity. In a mechanistic iron uptake study, 12 healthy male subjects (receiving comparable low phosphorus-containing meal typical for CKD patients: ≤1000 mg phosphate per day) were treated with 12 g (divided in 3 × 4 g) of stable (58)Fe isotope-labeled SBR759. The ferrokinetics of [(58)Fe]SBR759-related total iron was followed in blood (over 3 weeks) and in plasma (over 26 hours) by analyzing with high precision the isotope ratios of the natural iron isotopes (58)Fe, (57)Fe, (56)Fe and (54)Fe by multi-collector inductively coupled mass spectrometry (MC-ICP-MS). Three weeks following dosing, the subjects cumulatively absorbed on average 7.8 ± 3.2 mg (3.8-13.9 mg) iron corresponding to 0.30 ± 0.12% (0.15-0.54%) SBR759-related iron which amounts to approx. 5-fold the basal daily iron absorption of 1-2 mg in humans. SBR759 was well-tolerated and there was no serious adverse event and no clinically significant changes in the iron indices hemoglobin, hematocrit, ferritin concentration and transferrin saturation.

Isotope analysis of strontium by multicollector inductively-coupled plasma mass spectrometry: High-precision combined measurement of 88Sr/86Sr and 87Sr/86Sr isotope ratios

The paper describes a new high-precision method for the simultaneous precise determination of 88Sr/86Sr and 87Sr/86Sr ratios in a single portion of a geological sample by multicollector inductively coupled mass spectrometry (MC-ICP-MS). The isotope analysis is carried out with mass bias effect correction by a combination of internal normalization to the standard Zr-isotope ratio and bracketing standard method (external normalization). Our results for geochemical IAPSO and BCR-1 standard samples are in a good agreement with the published data. The reproducibility of the 88Sr/86Sr ratio varies from ±0.015 to ±0.05‰ (depending on the sample features) and, together with the analysis accuracy, is superior to the previously reported methods of MC-ICP-MS analysis. Still ahead is only double spike thermal ionization mass spectrometry with its ±0.02‰ reproducibility. However, the new method allows the simultaneous determination of 88Sr/86Sr and 87Sr/86Sr ratios and its productivity is higher by 5 to 6 times. On the other hand, in sample preparation, it is necessary to strive for at least 95% Sr yield from the chromatographic column; otherwise the sorption-desorption process may lead to a 0.6‰ 88Sr/86Sr ratio bias relative to the true value.

Silicon isotopic composition of boreal forest vegetation in Northern Sweden

Thorough characterization of the Si isotopic composition of the terrestrial biogenic pool could potentially allow Si isotope information to be used when assessing the relative contributions from biogenic and mineral sources to soil water, plants and surface waters. In the present study, the Si isotopic compositions of major biomass components in a boreal forest in Northern Sweden were investigated, along with the relative contributions from exogenous Si incorporated in the plant structure. This was achieved using chemical purification and high-resolution multi-collector inductively coupled mass spectrometry (MC-ICP-MS) for the precise and accurate determination of the Si isotopic composition of plants. The technique, which relies on multi-elemental analysis of plant ashes and sample-specific HF-dissolution followed by strong-anion exchange chromatography, allows efficient separation of Si from matrix and interfering elements, while recovering in excess of 99% Si. The long-term instrumental reproducibility, expressed as two standard deviations (2 σ), for the isotopic reference material NBS28 ( n = 12) was 0.06‰ for δ 29Si and 0.12‰ for δ 30Si. Results for the analyses of composite plant samples for the eight most prolific species in the boreal forest yielded a surprisingly homogenous Si isotopic composition, expressed as δ 29Si (± expanded combined uncertainty) and δ 30Si, ranging from (− 0.15 ± 0.11)‰ to (0.13 ± 0.06)‰ and (− 0.31 ± 0.08)‰ to (0.22 ± 0.13)‰, respectively. Isotopic and elemental analyses of local airborne particulate material suggest that the exogenous Si contribution varies between < 1% and > 70%, indicating that the potential surface contribution must be considered during Si uptake studies. The present study thus provides evidence that thorough appreciation of the forms of Si in plants is an absolute requirement when assessing the plant impact on the Si cycle via the difference in dissolution kinetics for phytoliths and lithogenic Si.

Hf isotope constraints on mantle sources and shallow‐level contaminants during Kerguelen hot spot activity since ∼120 Ma

We report new Hf isotopic data for basalts from the Kerguelen large igneous province (LIP) obtained using high‐precision multicollector inductively coupled mass spectrometry (MC‐ICP‐MS) analysis. All drill sites from the southern Indian Ocean Kerguelen Plateau–Broken Ridge, in addition to two volcanic suites from the Kerguelen Archipelago, are represented. These new data are integrated with other recently reported geochemical data for this LIP. We examine the geochemical signatures of the mantle sources and shallow‐level contaminants present during the past ∼120 Ma history of Kerguelen hot spot activity. Our results highlight the contribution of distinct mantle source compositions during Cretaceous (Kerguelen Plateau and Broken Ridge) and Cenozoic (northernmost Kerguelen Plateau and Kerguelen Archipelago) magmatism arising from melting of the Kerguelen plume head and plume tail, respectively. The Cretaceous Kerguelen plume basalts have primitive mantle‐like Pb, Sr, and Nd isotopic compositions and moderately depleted Hf isotopic compositions and are different from the Cenozoic plume basalts, which extend to more radiogenic Pb isotopic compositions. Neodymium and Hf isotopes are decoupled in Kerguelen plume‐derived rocks, and this, in combination with their Pb isotopic compositions, implies that the Kerguelen plume contains small amounts of ancient pelagic sediment mixed with old, recycled enriched oceanic crust. Different contributions from pelagic sediments relative to oceanic crust are able to account for the distinction between the isotopic compositions of the Cretaceous and Cenozoic mantle plume sources. Assimilation of shallow‐level continental crust, left stranded in the Indian Ocean during Gondwana breakup, by plume‐derived magmas was the dominant process recorded in Cretaceous Kerguelen Plateau basalts. During the Cenozoic, magmas from the Kerguelen plume mixed to varying degrees with local, Indian Ocean depleted upper mantle and assimilated the overlying Cretaceous Kerguelen Plateau lithosphere. Despite the geochemical heterogeneity of the Kerguelen LIP, we find evidence for a finite number of components involved in the genesis of Kerguelen Plateau–Broken Ridge and Kerguelen Archipelago rocks.

High precision isotope ratio measurements of mercury isotopes in cinnabar ores using multi-collector inductively coupled plasma mass spectrometry.

Variations in Hg isotope ratios in cinnabar ores obtained from different countries were detected by high precision isotope ratio measurements using multi-collector inductively coupled mass spectrometry (MC-ICP-MS). Values of delta198/202Hg varied from 0.0-1.3 percent per thousand relative to a NIST SRM 1641d Hg solution. The typical external uncertainty of the delta values was 0.06 to 0.26 percent per thousand. Hg was introduced into the plasma as elemental Hg after reduction by sodium borohydride. A significant fractionation of lead isotopes was observed during the simultaneous generation of lead hydride, preventing normalization of the Hg isotope ratios using the measured 208/206Pb ratio. Hg ratios were instead corrected employing the simultaneously measured 205/203T1 ratio. Using a 10 ng ml(-1) Hg solution and 10 min of sampling, introducing 60 ng of Hg, the internal precision of the isotope ratio measurements was as low as 14 ppm. Absolute Hg ratios deviated from the representative IUPAC values by approximately 0.2% per u. This observation is explained by the inadequacy of the exponential law to correct for mass bias in MC-ICP-MS measurements. In the absence of a precisely characterized Hg isotope ratio standard, we were not able to determine unambiguously the absolute Hg ratios of the ore samples, highlighting the urgent need for certified standard materials.