Isotope Ratio Measurements Research Articles

Lithium Isotope Enrichment Effects in Liquid Metal/Chloride Molten Salt System

The operation of fusion reactors requires the development of a 6Li enrichment process that does not have a negative impact on the environment. This study focuses on a new two-liquid-phase chemical exchange system, liquid-metal/chloride molten salt system. In this system, 6Li is distributed unevenly between immiscible liquid metal and chloride molten salt. After two-liquid contacting mixing, a quadrupole inductively coupled plasma spectrometry measurement was performed. The measured isotope ratio of 6Li to 7Li was corrected with mass bias compensation, and separation factor α was obtained. In both systems (Li/LiCl-KCl system, and Li-Pb/LiCl-KCl system), the α values were greater than 1 at 648 K almost at a 68% confidence interval, showing that more 6Li was likely distributed to liquid metal than to chloride molten salt. These results suggest that this system is applicable to enrich 6Li under optimal temperature conditions.

Faraday detector uranium isotope ratio measurement: Insights from solution- and laser ablation-based sampling methodologies on the Neoma MC-ICP-MS

In this study we utilize an all-faraday cup detector configuration on the Neoma MC-ICP-MS to perform uranium isotope ratio determinations from certified reference materials and a nuclear fuel precursor material via solution and laser ablation based sampling methodologies. The goal in performing these measurements is primarily to demonstrate that the all-faraday cup method can produce highly precise and accurate isotope ratios even at relatively low signal intensity levels while also developing a preliminary understanding of how the complex interplay between different amplifier resistor levels (e.g. 1011 vs 1013 Ω) and integration times impacts the precision and accuracy of different types of measurements. Our results show that the faraday cups with 1013 Ω resistors in their amplifier feedback loops can be used to produce accurate and relatively precise isotope ratios for ion beams down to ∼5 K cps. However, at the lower end of the signal intensities observed in this study, longer integration times are necessary to mitigate the impact of ion beam instability that can occur during laser ablation based sampling. Despite this potential limitation, the all-faraday cup method is highly versatile as exemplified by the analysis of a collection of uranium reference materials with highly variable uranium isotopic compositions.

Developments in analytical techniques for chemostratigraphy, chronostratigraphy, and geochemical fingerprinting studies: Current status and future trends

Chemostratigraphy utilizes the elemental, isotopic, and mineralogical compositions of sediments and rocks to understand the conditions of deposition and diagenesis, variations in paleo-redox conditions, climate, provenance, tectonic setting, and reservoir characteristics. This utility is based on the occurrences and stratigraphic variations of concentrations of certain elements, isotopes, minerals, and some organic compounds in sedimentary rocks. Significant progress has been made in the elemental, isotopic, and mineralogical determination techniques over the last couple of decades and this development is critically helpful to the applications of chemostratigraphy in widely varying fields including, but not limited to stratigraphy, depositional and diagenetic modelling, petroleum exploration, reservoir characterization, forensics, etc. Currently, highly precise data on about 60 elements in the range Li–U can be obtained very rapidly on a routine basis in different types of sediment samples such as drill cuttings, sediment cores, or hand specimens using various analytical techniques such as inductively coupled plasma mass spectrometry (ICP-MS), high resolution ICP-MS (HR-ICP-MS), and Mattauch–Herzog geometry ICP-MS (MH-ICP-MS). Elemental data as ratios of certain elements or proxy values in profile form with depth, isotope values, and certain ratios are used for understanding various geological processes in the earth's history. Mineralogical studies using techniques such as x-ray diffraction spectrometry (XRD) and Raman spectroscopy have proven to be very powerful for identifying different sedimentary successions belonging to different ages. There have been notable advances in the measurement of isotopic concentrations and isotopic ratios both in stable isotopes and radiogenic isotopes. Certain analytical techniques such as laser-induced breakdown spectroscopy (LIBS) are able to distinguish different rock types, their geographic sources, and the geological processes associated with their formation in a field setting in real-time. In addition to the instrumental developments, substantial progress is made in other critical areas such as sample preparation, sample decomposition, analytical protocols, development of international certified geochemical reference materials (CRMs), and quality issues in general. Until recently, the general approach in elemental and mineralogical chemostratigraphic studies was to follow time taking process of collecting the sediment/drill core samples in the field and bringing them to the laboratory to generate the analytical data. This is very expensive, time-consuming, and difficult for covering large areas. But, rapid advances in the area of analytical instrumentation saw some instruments such as x-ray fluorescence spectrometer (XRF), LIBS, visible and near-infrared spectrophotometer, and Raman spectrometer dramatically shrunk in size and have become portable, and changed this scenario completely and increased on-site applications in chemostratigraphy studies. In this review, these developments in analytical instrumentation in general together with some key applications in chemostratigraphy, chronostratigraphy, and geochemical fingerprinting have been summarized.

High-precision zinc isotope measurement of chemically different geostandards by multicollector inductively coupled plasma mass spectrometry.

Zinc isotopes are becoming increasingly applicable in high-temperature geochemistry, for example in crust-mantle interaction and volatilization-related processes. The published zinc isotope data for some commonly used reference materials, however, show large interlaboratory offsets. In addition, there is still limited data for zinc isotope compositions of many widely used geological reference materials. For precise and accurate zinc isotopic ratio analysis of chemically diverse geostandards, including ultramafic to felsic igneous rocks, carbonatites, sediments and soils, an improved procedure for chemical purification of zinc was introduced in this study. The factors potentially affecting zinc isotopic ratio measurement were assessed. The accuracy and long-term reproducibility were obtained by measurements on both synthetic solutions and well-characterized geostandards. Purification of geologic samples with different zinc concentrations and matrix compositions yields consistent elution curves with nearly 100% recovery. Acidity and concentration mismatches and the presence of some matrix elements (e.g., Mg, Ti and Cr) have significant impacts on the precision and accuracy of zinc isotopic ratio measurement. The zinc isotope compositions of a suite of reference materials were measured using this method. The present study describes methods for the chemical purification of zinc and high-precision and accurate zinc isotopic ratio measurements using multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS). The long-term external reproducibility for δ66 Zn values is ±0.04‰ (2SD). High-quality zinc isotope data of chemically different geostandards were reported to stimulate future interlaboratory calibrations.

Characterisation of Conventional 87Sr/86Sr Isotope Ratios in Cement, Limestone and Slate Reference Materials Based on an Interlaboratory Comparison Study

An interlaboratory comparison (ILC) was organised to characterise 87Sr/86Sr isotope ratios in geological and industrial reference materials by applying the so‐called conventional method for determining 87Sr/86Sr isotope ratios. Four cements (VDZ 100a, VDZ 200a, VDZ 300a, IAG OPC‐1), one limestone (IAG CGL ML‐3) and one slate (IAG OU‐6) reference materials were selected, covering a wide range of naturally occurring Sr isotopic signatures. Thirteen laboratories received aliquots of these six reference materials together with a detailed technical protocol. The consensus values for the six reference materials and their associated measurement uncertainties were obtained by applying a Gaussian, linear mixed effects model fitted to all the measurement results. By combining the consensus values and their uncertainties with an uncertainty contribution for potential heterogeneity, reference values ranging from 0.708134 mol mol‐1 to 0.729778 mol mol‐1 were obtained with relative expanded uncertainties of ≤ 0.007 %. This study represents an ILC on conventional 87Sr/86Sr isotope ratios, within which metrological principles were considered and the compatibility of measurement results obtained by MC‐ICP‐MS and by MC‐TIMS is demonstrated. The materials characterised in this study can be used as reference materials for validation and quality control purposes and to estimate measurement uncertainties in conventional 87Sr/86Sr isotope ratio measurement.

Low‐Coherence Photothermal Interferometry for Precision Spectroscopic Gas Sensing

AbstractLaser spectroscopy has shown great potential as a cost‐effective method for trace gas detection with high sensitivity and specificity. However, it still falls short in applications such as the measurement of stable isotope ratios, which require high precision and stability. Here, ultrasensitive gas detection with remarkable precision and stability as well as better immunity to isobaric interference is demonstrated by use of low‐coherence photothermal interferometry. With a 10 cm long hollow‐core fiber, acetylene detection is achieved with a noise‐equivalent concentration of 0.7 part‐per‐billion and measurement precision of 0.025%. The instability of the detection over a period of 3 h is ±0.038%, 10 times better than the state‐of‐the‐art photothermal spectroscopy. The measurement of the 13C/12C isotope ratio of acetylene is demonstrated with measurement precision of ≈0.01%. This study highlights the potential of low‐coherence photothermal interferometry as an alternative to mass spectrometers, offering reliable gas detection in a compact form.

Salinity spatial patterns in Mediterranean coastal areas: The legacy of historical water infrastructures

Mediterranean coastal areas have been occupied and developed intensively for a long time facing issues related to agricultural production, urbanization, tourism, preservation of natural resources often linked to salinity. This article explores the relationship between historical land planning and water management, and current soil and water salinity to gain insights into future projections.Soil samples (1185) were collected in a coastal plain of 114 km2 in the south of France and saturated paste extract Electrical Conductivity (ECsp) was deduced from 1:5 dilution. Soil salinity exhibits a wide range of variation (from 0.54 to 113.1 mS cm−1) and spatial patterns. ECsp is significantly different among soil types, higher at depth than at the surface and influenced by the distance to ancient water infrastructures (Pettitt test). Surface water and shallow groundwater samples were collected for trace element concentrations and Oxygen (18O/16O) isotope ratio measurements. The geochemical signatures indicate a mixture between surface freshwater and seawater, reveal the presence of over-salted seawater and a stratification of salinity from the surface to the depth.Results suggest that groundwater is the source of soil salinity, and illustrate the long-term impact of old water infrastructures. Less saline soils are found near the freshwater supply channel (constructed from 15th to 18th), while more saline soils are located near drainage channels. The presence of over-salted water reflects temporal evolution of the plain over the last few centuries (initially under seawater, gradually filled in, presence of ponds and salt works that have now disappeared). The current soil salinity patches continue to be a visible reminder of this evolution. The trend towards desalinization of the plain over the last few centuries has been made possible by massive freshwater inflows, which are now under threat due to the general decrease of water resources availability.

Artefacts from Ban Chiang, Thailand: Pre-metal Age cord-marked pottery

Abstract Pottery excavated from the archeological UNESCO world heritage site Ban Chiang in Thailand stem from distinct periods. Black vessels with cord-mark design from Pre-metal Age (ca. 3000–1000 BC), Bronze Age pottery (ca 1000–300 BC) with yellow-brown surface and Iron Age samples (ca. 300 BC–200 AD) with red pictorial surface patterns. In a previous work [Bismayer U., Srilomsak S., Treekamol Y., Tanthanuch W., Suriyatham K. Artefacts from Ban Chiang, Thailand: pottery with hematite-red geometric patterns. Z. Kristallogr. 2020, 235, 559–568] we studied the mineralogical composition and their surface colour materials of shards from Bronze and Iron Age. In this work we focus on bulk features of the dark Pre-metal Age cord-marked ceramic shard PSN2-S10E13 and compare its elemental and mineralogical composition with bulk composition of sample 5412-S6E15 from Bronze Age. Experimental techniques are electron microprobe, X-ray powder diffraction, FTIR spectroscopy, optical microscopy and X-ray tomographic microscopy (XTM). Sample PSN2-S10E13 contains more quartz than 5412-S6E15. In the bulk of the Pre-metal Age shard, diffraction signals of mullite occur, indicating higher firing temperatures compared to the younger sample. Phyllosilicate signals are seen in FTIR spectra of both shards. E-modes of quartz dominate FTIR spectra of both samples. Optical thin sections show voids around micro-particles in PSN2-S10E13 and XTM indicates that the pore volume percentage of sample PSN2-S10E13 is higher than in 5412-S6E15. Because of the large age gap to younger samples from Ban Chiang, the proper age of our oldest sample PSN2-S10E13 was determined using an accelerator mass spectrometer (AMS) by simultaneous 14C/12C and 13C/12C isotope ratio measurements which yielded a radiocarbon age of 3609 ± 29 BP (resp. 1659 ± 29 BC).

A year-round observation of δ13C of dicarboxylic acids and related compounds in fine aerosols: Implications from Central European background site

Isotopic analysis of specific compounds in aerosols can be a useful tool when studying atmospheric processes. Here, we present the results of stable carbon isotope ratio (δ13C) measurements performed on a one-year set (n = 96, Sep. 2013–Aug. 2014) of dicarboxylic acids and related compounds in PM1 at a rural Central European background site, Košetice (Czech Republic).The most 13C enriched acid was oxalic (C2, annual average = −16.6 ± 5.0‰) followed by malonic (C3, avg. = −19.9 ± 6.6‰) and succinic (C4, avg. = −21.3 ± 4.6‰) acids. Thus, δ13C values decreased with an increase in carbon numbers. Azelaic acid (C9, avg. = −27.2 ± 3.6‰) was found to be the least 13C enriched.A comparison of δ13C of dicarboxylic acids from other background sites, especially in Asia, shows similar values to those from the European site. This comparison also showed that C2 is more 13C enriched at background sites than at urban ones. In general, we did not observe significant seasonal differences in δ13C values of dicarboxylic acids at the Central European station. We observed statistically significant differences (p value < 0.05) between winter and summer δ13C values solely for C4, glyoxylic acid (ωC2), glutaric acid (C5) and suberic acid (C8).The only significant correlations between δ13C of C2 and δ13C of C3 were found in spring and summer, suggesting that the oxidation of C3 to C2 is significant in these months with a strong contribution from biogenic aerosols. The strongest season-independent annual correlation was observed in δ13C values between C2 and C4, the two dominant dicarboxylic acids. Therefore, C4 appears to be the main intermediate precursor of C2 throughout the whole year.

Development of three chalcopyrites and one copper metal as potential reference materials for copper isotopic analysis by LA-MC-ICP-MS.

Laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) has become a powerful technique for in situ Cu isotopic analysis in natural geological samples. Cu isotopic compositions in natural chalcopyrites have been used to reveal aspects of the mineralization processes directly. However, internationally or commercially available matrix-matched chalcopyrite reference materials for mass fractionation correction or quality control purposes are still lacking for in situ Cu isotopic analysis using LA-MC-ICP-MS. Three natural chalcopyrites 14ZJ12-1, JGZ-29 and JGZ-78, and one copper metal GBW02141 with different Cu isotopic compositions were investigated as potential microanalytical reference materials by LA-MC-ICP-MS. Ga element was used as an internal standard to correct the mass fractionation of Cu isotopes during LA-MC-ICP-MS analysis. A large number of Cu isotope ratio measurements using femtosecond LA-MC-ICP-MS were conducted and produced good intermediate precision of δ65 CuNIST976 (0.07-0.08‰, 2 standard deviations), demonstrating the homogeneous Cu isotopic distribution in the recommended samples. The mean δ65 CuNIST976 values of -0.21 ± 0.04‰, 0.46 ± 0.04‰, -0.06 ± 0.04‰ and 0.11 ± 0.05‰ (2 standard deviations) in 14ZJ12-1, JGZ-29, JGZ-78 and GBW02141, respectively, were obtained using solution-MC-ICP-MS in the four recommended samples. Here, we describe three natural chalcopyrites 14ZJ12-1, JGZ-29, JGZ-78, and one copper metal GBW02141 as the potential Cu isotopic reference materials for LA-MC-ICP-MS analysis. Our analyses demonstrate that these recommended materials have a high degree of elemental and isotopic homogeneity, indicating that they are suitable for microanalysis techniques for data quality assurance or interlaboratory calibration.

Accuracy and precision of ESI-Orbitrap-IRMS observations of hours to tens of hours via reservoir injection

Orbitrap isotope ratio mass spectrometry (Orbitrap-IRMS) has recently been applied to high-precision, natural-abundance isotope ratio measurements of a diverse range of compounds, including amino acids, oxyanions, fatty acids, and metals. These measurements can characterize many isotope ratios simultaneously at high (≈1.0‰) precision. In a successful experiment, observed precision will track the shot-noise limit and be limited by experimental time. Some isotope ratios, for example those involving 17O in organic compounds or multiply-substituted (‘clumped’) isotopologues, require experimental times of hours to tens of hours to achieve desired precision, while current sample introduction techniques focus on observations on the order of seconds to tens of minutes. In this study, we characterize Orbitrap-IRMS performance for three long duration measurements (individual acquisitions ≥1 h and as long as 24 h) using an automated reservoir injection system coupled to a Q Exactive HF Orbitrap with an electrospray ionization (ESI) source. First, we characterize long-term intra-measurement stability through a 24-h long measurement of acetone. We report the following isotope ratios and precisions (as acquisition errors, errors on the observed ratio within this measurement (σAE)): 13C/12C (σAE = 0.07‰), 17O/16O (σAE = 1.1‰), 18O/16O (σAE = 0.3‰), and 13C13C/12C (σAE = 0.65‰). The σAE of each tracks the shot noise limit throughout and is limited by the challenging conditions (high resolution and low numbers of ions per scan) required for 17O/16O measurement in the presence of 13C via Orbitrap. Second, we characterize inter-measurement stability via a sequence of seven 75-min analyses of perchlorate. We observe the following ratios and acquisition errors: 37Cl/35Cl (σAE = 0.09‰); 17O/16O (σAE = 1.6‰); 18O/16O (σAE = 0.7‰), 37Cl17O/35Cl16O (σAE = 2.7‰), and 37Cl18O/35Cl16O (σAE = 1.2‰). However, we find that inter-measurement drift between acquisitions limits our accuracy and precision for standardized measurements (i.e., error on reported δ values) to ≈1‰ for the 37Cl/35Cl measurement. Hence, the benefits of low σAE may not be fully realized. Third, we demonstrate accuracy via sample/standard comparisons of a methionine sample with 13C enrichment of ≈20‰ relative to a known standard. Using a sequence of seven 60-min analyses, we recover the following isotope ratios and standardized precisions (i.e., error on reported δ values, denoted propagated acquisition errors, σPAE): 33S/32S (σPAE = 1.0‰), 34S/32S (σPAE = 0.7‰), 15N/14N (σPAE = 2.1‰), 2H/1H (σPAE = 3.2‰),13C/12C (σPAE = 0.4‰), 18O/16O (σPAE = 1.6‰), &13C13C/12C (σPAE = 2.8‰) with confirmation of accurate results for the known 13C/12C and 13C13C/12C enrichments. Together, our results demonstrate the viability of Orbitrap-IRMS for long duration measurements of diverse sample types via an automated reservoir injection system. Inter-measurement stability remains a challenge; we expect our methods to be most applicable to extended measurements of hard-to-observe properties, such as 17O in organics and clumped isotopologues.

Multiple Technology Approach Based on Stable Isotope Ratio Analysis, Fourier Transform Infrared Spectrometry and Thermogravimetric Analysis to Ensure the Fungal Origin of the Chitosan.

Chitosan is a natural polysaccharide which has been authorized for oenological practices for the treatment of musts and wines. This authorization is limited to chitosan of fungal origin while that of crustacean origin is prohibited. To guarantee its origin, a method based on the measurement of the stable isotope ratios (SIR) of carbon δ13C, nitrogen δ15N, oxygen δ18O and hydrogen δ2H of chitosan has been recently proposed without indicating the threshold authenticity limits of these parameters which, for the first time, were estimated in this paper. In addition, on part of the samples analysed through SIR, Fourier transform infrared spectrometry (FTIR) and thermogravimetric analysis (TGA) were performed as simple and rapid discrimination methods due to limited technological resources. Samples having δ13C values above -14.2‱ and below -125.1‱ can be considered as authentic fungal chitosan without needing to analyse other parameters. If the δ13C value falls between -25.1‱ and -24.9‱, it is necessary to proceed further with the evaluation of the parameter δ15N, which must be above +2.7‱. Samples having δ18O values lower than +25.3‱ can be considered as authentic fungal chitosan. The combination of maximum degradation temperatures (obtained using TGA) and peak areas of Amide I and NH2/Amide II (obtained using FTIR) also allows the discrimination between the two origins of the polysaccharide. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) based on TGA, FTIR and SIR data successfully distributed the tested samples into informative clusters. Therefore, we present the technologies described as part of a robust analytical strategy for the correct identification of chitosan samples from crustaceans or fungi.

The Material Complexity of Three Seventeenth-Century Cabinets Exported from the Far East

ABSTRACT This paper focuses on three Far East cabinets that have ended up in Sweden for various reasons and on various routes. Some specific characteristics have been analysed using various scientific methods: sectional microscopy, wood taxonomy, X–ray fluorescence microscopy, pyrolysis-gas chromatography-mass spectrometry, strontium isotope ratio measurement, and radiocarbon dating. The results show that the cabinets contain wood from species endemic to Japan, namely asunaro (Thujopsis dolabrata) and hinoki (Chamaecyparis obtuse). They are coated with urushi sap derived from Toxicodendron vernicifluum trees, in two cases confirmed to be harvested in China, and one case probably blended with sap exuded from Toxicodendron succedanea harvested in North Vietnam. Their black appearance is due to a soot pigment typical of many products from the early Edo period or older. The data obtained with scientific methods, unavailable in the past, improve knowledge about these cabinets. Such new information should be made available to scholars and the general public.

Application of elemental analysis-coupled isotope ratio mass spectrometry for protein turnover analysis using deuterium labeling: Purification and analysis of hydrogen isotope ratio of non-derivatized protein-bound alanine.

Heavy water can be used as a tracer for the evaluation of protein turnover. By adding heavy water (D2 O) to the precursor pool, nonessential amino acids, including alanine, can be isotopically labeled in vivo. Protein turnover can then be quantified by measuring the hydrogen isotope ratio of protein-bound alanine. In this study, we constructed a novel method to apply deuterium labeling of alanine to the evaluation of protein turnover using elemental analysis-coupled isotope ratio mass spectrometry (EA-IRMS). We established a preparative high-performance liquid chromatography method to isolate alanine from protein hydrolysates. EA-IRMS was then used to determine the hydrogen isotope ratio of alanine isolated from hydrolysates of protein from mouse myoblast C2C12 cells that had been treated with D2 O over the course of 72 h. In cells treated with 4% D2 O, the deuterium enrichment of alanine increased to approximately 0.9% over time, while that of cells treated with 0.017% D2 O increased to approximately 0.006%. The rate of protein synthesis calculated by fitting the increase of deuterium excess to rise-to-plateau kinetics was similar regardless of the concentration of D2 O. When C2C12 cells treated with insulin and rapamycin were analyzed 24 h after the addition of 0.017% D2 O, protein turnover was found to be accelerated by insulin, but this effect was offset by co-treatment with rapamycin. The derivative-free measurement of the hydrogen isotope ratio of protein-bound alanine using EA-IRMS can be applied to the evaluation of protein turnover. The proposed method is an accessible option for many laboratories to perform highly sensitive IRMS-based evaluations of protein metabolic turnover.

A new era of plutonium assay and isotope ratio measurements at ultra-low levels in IAEA safeguards environmental swipe samples by isotope dilution MC-ICP-MS using a 244Pu spike

A new era of plutonium assay and isotope ratio measurements at ultra-low levels in IAEA safeguards environmental swipe samples by isotope dilution MC-ICP-MS using a 244Pu spike

Analytical performance of single particle aerosol mass spectrometer for accurate sizing and isotopic analysis of individual particles

The commercial Hexin Single particle aerosol mass spectrometer (SPAMS) has been widely used for environmental aerosol monitoring and source apportionment. However, particle size measurement is easily affected by environment pressure fluctuation and sampling orifice clogging. The capability for quantitative analysis is poor, and few isotope measurement has been reported. This paper aims to evaluate the analytical performance of SPAMS and extend its application. First, the flight time of standard particles having different densities and sizes was measured under various conditions (aerodynamic lens upstream pressure and carrier gas). We proposed a universal method for particle size calibration, measurement and correction, taking into account the effects of lens geometry (acceleration nozzle diameter), particle parameters (density, diameter, and shape factor), and operating conditions (lens upstream pressure and carrier gas). Then, isotope measurement was performed when introducing a solution droplet containing a single element. Metal oxide and metal cluster ions were observed in the mass spectrum, indicating incomplete ionization of the sample droplet. The mass discrimination effect was carefully evaluated to correct the measured isotope ratio. Results show that the achievable accuracy of the corrected isotope ratio for elements investigated was 5%. The instrumental performance was relatively poor for elements having great ionization potential or bond energy. Finally, Ag/Eu2O3 suspension and yellow cake/ethanol suspension were analyzed for size, elemental and isotopic analysis. We confirmed that the mass discrimination effect during suspension introduction could be corrected using the mass discrimination correction factor obtained during solution introduction. The Ag, Eu and U in these suspension particles were all found to be at natural abundance. The uranium in the yellow cake was identified as sodium duranyate (Na2U2O7) with volumetric equivalent diameter of approximately 65 nm. The work presented here is beneficial for instrument improvement and wide application.

Optimization of a Picarro L2140-i cavity ring-down spectrometer for routine measurement of triple oxygen isotope ratios in meteoric waters

Abstract. The demanding precision of triple oxygen isotope (Δ17O) analyses in water has restricted their measurement to dual-inlet mass spectrometry until the recent development of commercially available infrared laser analyzers. Laser-based measurements of triple oxygen isotope ratios are now increasingly performed by laboratories seeking to better constrain the source and history of meteoric waters. However, in practice, these measurements are subject to large analytical errors that remain poorly documented in scientific literature and by instrument manufacturers, which can effectively restrict the confident application of Δ17O to settings where variations are relatively large (∼ 25–60 per meg). We present our operating method of a Picarro L2140-i cavity ring-down spectrometer (CRDS) during the analysis of low-latitude rainwater where confidently resolving daily variations in Δ17O (differences of ∼ 10–20 per meg) was desired. Our approach was optimized over ∼ 3 years and uses a combination of published best practices plus additional steps to combat spectral contamination of trace amounts of dissolved organics, which, for Δ17O, emerges as a much more substantial problem than previously documented, even in pure rainwater. We resolve the extreme sensitivity of the Δ17O measurement to organics through their removal via Picarro's micro-combustion module, whose performance is evaluated in each sequence using alcohol-spiked standards. While correction for sample-to-sample memory and instrumental drift significantly improves traditional isotope metrics, these corrections have only a marginal impact (0–1 per meg error reduction) on Δ17O. Our post-processing scheme uses the analyzer's high-resolution data, which improves δ2H measurement (0.25 ‰ error reduction) and allows for much more rich troubleshooting and data processing compared to the default user-facing data output. In addition to competitive performance for traditional isotope metrics, we report a long-term, control standard root mean square error for Δ17O of 12 per meg. Overall performance (Δ17O error of 6 per meg, calculated by averaging three replicates spread across distinct, independently calibrated sequences) is comparable to mass spectrometry and requires only ∼ 6.3 h per sample. We demonstrate the impact of our approach using a rainfall dataset from Uganda and offer recommendations for other efforts that aim to measure meteoric Δ17O via CRDS.

Oxygen and chlorine isotope fractionation during microbial perchlorate reduction in static and flow through systems

Perchlorate (ClO4−) is an oxyanion with both anthropogenic and natural sources that is widespread on earth and throughout the solar system. Stable isotope ratio measurements are a powerful tool to assess the origin and predict the fate of perchlorate in the environment. The aim of this study was to perform an experimental survey of parameters that influence microbial O and Cl isotope fractionation during microbial perchlorate reduction, covering microbiological (genetic background and community context) and environmental (temperature, salinity, electron donor type and limitation) factors. A new method for the purification of perchlorate for isotope ratio mass spectrometry (IRMS) was developed to allow for more efficient sample preparation and suitable for samples containing small amounts of perchlorate (0.4–2 mg). Although most experiments, regardless of treatment, yielded a consistent isotope enrichment factor ratio (Λ = ε18O/ε37Cl ∼ 2.5), a greater variability was observed of individual isotope enrichment factors (ε18O and ε37Cl). Although most experiments yielded isotope enrichment factors (epsilon) in the larger negative range of previously published values, smaller negative values of ε18O and ε37Cl were observed for a halophilic isolate, Haloarcula marismortui, (ε18O = −15 to −22‰ and ε37Cl = −5 to −7‰), and in sediment column experiments (ε18O = −4 to −15‰ and ε37Cl = −1 to −6‰). Given the complexity of isolating individual parameters from our proposed model, we view our dataset as a survey that points to future opportunities where a particular parameter could be isolated to better understand controls on O and Cl isotope fractionation during microbial perchlorate reduction.

Low-cost and sensitive method for Pb isotope determination using a novel β-Si3N4 emitter by thermal ionization mass spectrometry

Thermal ionization mass spectrometry (TIMS) is the workhorse for lead isotopic ratio analysis due to its excellent precision. Silica gel as ionization activator on Re filament is proved to the best emitter that can provide excellent sensitivity even small Pb sample size. However, the price of Re filament is three times that of Ta filament that leads to high experimental cost for TIMS laboratory. Here, we first present a novel silicon nitride (β-Si3N4) emitter on the Ta filament with good sensitivity for Pb isotopic ratio measurements. Hence, the cost of filament material is cut down ∼70%. The β-Si3N4 emitter can yield stable and long-life Pb+ signal, about 2–3 V 208Pb and 0.65–0.90 V 208Pb for 20 ng and 5 ng NIST SRM981 sample size that is applicable to the most geological materials for bulk analysis. A suite of silicate reference materials were analyzed to verify the reliability and accuracy of our method. For 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb isotope ratios of geological samples, excellent internal precisions (2 SE) of ±0.005%–0.013% are achieved. Replicate digestions and analyses of the basalt standard BCR-2 and coal fly ash standard GBW08401 demonstrate that good external precision is obtainable that is 0.10–0.18% (n = 6, 2 SD) for 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios.

Estimate of Neutron Fluence Using Isotope Ratio Method for ZR-2.5NB Materials Irradiated in the National Research Universal Reactor

Abstract The isotope ratio method (IRM) is a technique used for estimating the energy production in a fission reactor by measuring isotope ratios in nonfuel reactor components. This method has been successfully demonstrated on the estimation of cumulative energy production as well as plutonium production in graphite-moderated and light-water-moderated reactors for nonproliferation purposes. In this paper, IRM was used to estimate neutron fluence in Zr-2.5Nb materials irradiated in fast neutron (FN) irradiation facilities in the National Research Universal (NRU) reactor. Neutron fluence has been shown to be an important parameter for studying irradiation effects on the performance and properties of critical reactor components. Selected isotope ratios of hafnium and iron were used as indicators of the neutron fluence in Zr-2.5Nb sample materials. Correlations between neutron fluence and the indicator element isotope ratios were generated using the reactor physics simulation codes Winfrith improved multigroup scheme (WIMS)-AECL and SCALE/Oak Ridge Isotope GENeration code (ORIGEN). Inductively coupled plasma-mass spectrometry (ICP-MS) was used to obtain accurate measurements of the isotope ratios. Neutron fluence values estimated using IRM, were in good agreement with the values based on measured irradiation power histories of the NRU reactor. This study proposes a potential application of IRM to the estimation of neutron fluence for critical reactor components in heavy-water-moderated reactors such as pressure and calandria tubes in CANDU® reactors.