New on-line method for water isotope analysis of speleothem fluid inclusions using laser absorption spectroscopy (WS-CRDS) (original) (raw)
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Rapid Communications in Mass Spectrometry, 2013
RATIONALE: The hydrogen and oxygen isotopic analyses (δ 2 H and δ 18 O values) of water trapped within speleothem carbonate (fluid inclusions) have traditionally been conducted utilizing dual-inlet isotope ratio mass spectrometry (IRMS) or continuous-flow (CF)-IRMS methods. The application of cavity ring-down spectroscopy (CRDS) to the δ 2 H and δ 18 O analysis of water in fluid inclusions has been investigated at the University of Miami as an alternative method to CF-IRMS. METHODS: An extraction line was developed to recover water from the fluid inclusions consisting of a crusher, sample injection port and an expansion volume (either 100 or 50 cm 3) directly connected to the CRDS instrument. Tests were conducted to determine the reproducibility of standard water injections and crushes. In order to compare results with conventional analytical methods, samples were analyzed both at the University of Miami (CRDS method) and at the Vrije Universiteit Amsterdam (CF-IRMS method). RESULTS: The analytical reproducibility of speleothem samples crushed on the Miami Device demonstrates an average external standard deviation of 0.5 and 2.0 ‰ for δ 18 O and δ 2 H values, respectively. Sample data are shown to fall near the global meteoric water line, supporting the validity of the method. Three different samples were analyzed at Vrije Universiteit Amsterdam and the University of Miami in order to compare the performance of each laboratory. The average offset between the two laboratories is 0.7 ‰ for δ 18 O and 2.5 ‰ for δ 2 H. CONCLUSIONS: The advantage of CRDS is that the system is a low-cost alternative to CF-IRMS for fluid inclusion isotope analysis. The CRDS method demonstrates acceptable precision and good agreement with results from the CF-IRMS method. These are promising results for the future application of CRDS to fluid inclusion isotope analysis.
Rapid Communications in Mass Spectrometry, 2020
Online oxygen (δ 18 O) and hydrogen (δ 2 H) isotope analysis of fluid inclusion water entrapped in minerals is widely applied in paleo-fluid studies. In the state of the art of fluid inclusion isotope research, however, there is a scarcity of reported inter-technique comparisons to account for possible analytical offsets. Along with improving analytical precisions and sample size limitations, interlaboratory comparisons can lead to a more robust application of fluid inclusion isotope records. Methods: Mineral samples-including speleothem, travertine, and vein materialwere analyzed on two newly setup systems for fluid inclusion isotope analysis to provide an inter-platform comparison. One setup uses a crusher unit connected online to a continuous-flow pyrolysis furnace and an isotope ratio mass spectrometry (IRMS) instrument. In the other setup, a crusher unit is lined up with a cavity ringdown spectroscopy (CRDS) system, and water samples are analyzed on a continuous standard water background to achieve precisions on water injections better than 0.1‰ for δ 18 O values and 0.4‰ for δ 2 H values for amounts down to 0.2 μL. Results: Fluid inclusion isotope analyses on the IRMS setup have an average 1σ reproducibility of 0.4‰ and 2.0‰ for δ 18 O and δ 2 H values, respectively. The CRDS setup has a better 1σ reproducibility (0.3‰ for δ 18 O values and 1.1‰ for δ 2 H values) and also a more rapid sample throughput (<30 min per sample). Fluid inclusion isotope analyses are reproducible at these uncertainties for water amounts down to 0.1 μL on both setups. Fluid inclusion isotope data show no systematic offsets between the setups. Conclusions: The close match in fluid inclusion isotope results between the two setups demonstrates the high accuracy of the presented continuous-flow techniques for fluid inclusion isotope analysis. Ideally, experiments such as the one presented in this study will lead to further interlaboratory comparison efforts and the selection of suitable reference materials for fluid inclusion isotopes studies.
The recovery and isotopic measurement of water from fluid inclusions in speleothems
Geochimica et Cosmochimica Acta, 2001
The isotopic composition of speleothems is a useful palaeoclimatic indicator, but its value would be enhanced if information on the composition of the parent dripwaters could be recovered from fluid inclusions in the speleothem calcite. To develop a robust method for extracting and measuring oxygen and hydrogen isotopic composition of fluid inclusions we have used anhydrous Iceland Spar and microlitre glass capillaries of water as an analogue system. Crushing the capillary and calcite together in a high vacuum cell we have investigated the adsorbtive and isotopic behaviour of water when exposed to clean fracture surfaces. Significant water adsorption occurs at room temperature, accompanied by large negative isotopic shifts of both oxygen and hydrogen in the recovered free water at H 2 O/CaCO 3 mass ratios Ͻ10 mg g Ϫ1 . Cryogenic pumping fails to achieve total desorption. The degree of depletion is inversely related to the water/calcite ratio, fractionation of hydrogen isotopes exceeding Ϫ20‰, and oxygen isotopes Ϫ10‰, at ratios typically observed in natural speleothems. Heating the crushed calcite at 150°C for 60 min. totally desorbs the water and allows retrieval of the correct isotopic composition. Application of these methods to a British Late Holocene speleothem yields ␦ 18 O and ␦ 2 H compositions for the inclusion water which are closely comparable with the modern cave dripwaters and local precipitation. The results show that isotopic compositions can be recovered from inclusion samples of Ͻ1L (equivalent to approximately 1g of calcite) with precisions that are useful for palaeoclimatic research, Ϯ0.4‰ for ␦ 18 O and Ϯ3‰ for ␦ 2 H. Greater precision than this will require replicate analysis for each speleothem growth increment.
2002
This thesis is one of the results of a research project at the Centrum voor IsotopenOnderzoek (CIO) of the University of Groningen. Dr. Harro Meijer started the project in 1993 and it was set going with some preliminary measurements at the University of Nijmegen, in cooperation with dr. ir. Nico Dam and prof. dr. Jörg Reuss. When a proposal was granted by the stichting Fundamenteel Onderzoek der Materie (FOM), a color center laser and other equipment was purchased. Then dr. ir. Erik Kerstel joined the project and Jaap van der Ploeg, an electro-technicien, was put on the work as well. In 1997 I joined the team. Erik received a prestigeous grant as a Research Fellow from the Koninklijke Nederlandse Academie van Wetenschappen (KNAW) and, after that ended, he received a permanent position within the CIO, thus ensuring the continuation of the project. The project aimed to develop a new method for measuring the relative stable isotope ratios of 18 O/ 16 O, 17 O/ 16 O and 2 H/ 1 H in water. During my contract, the research group was supposed to develop thr method up to a level where it could be employed to real-world applications. My work was scheduled to end after the application of the method to some interesting fields, namely biomedicine and paleoclimatology. The present thesis reports on our collective results which were achieved during my presence at the CIO, but could never have been completed without the work already done in the period before my arrival. Chapter 1 of this thesis provides some general information on the field of isotope physics as studied within the CIO. Chapter 2 gives detailed information on the current measurement setup and the underlying principles. In Chapter 3 an overview is given of the results of the measurements on biomedical (enriched) samples, while Chapter 4 shows the results of the measurements on a deep Greenland ice core. Chapter 5 describes a more exotic application of the technique. In Chapter 6, finally, an outlook of further expected developments is given.
Rapid Communications in Mass Spectrometry, 2009
An analytical line for stable isotope analyses of water recovered from fluid inclusions in minerals was built and successfully tested. The line is based on the principle of continuous-flow analysis of water via high-temperature reduction on glassy carbon. It includes a custom-designed set of high-efficiency crushers and a cryo-focusing cell. This paper provides details of the line design and discusses strategies for line conditioning and mitigation of memory effects. The line allows measurements of hydrogen and oxygen isotopes during a single acquisition. The precision of the analyses depends on the amount of water released from the inclusions. The best results are obtained for samples containing at least 0.1–0.2 µL (0.06–0.11 µmol) H2O. For such samples precision is better than 1.5‰ for δD and 0.5‰ for δ18O (1σ). Smaller amounts of water can be measured but at lower precision. Analyses of modern calcite formed under stable conditions in a deep cave allowed assessment of the accuracy of the analyses. The δD values measured in fluid inclusions of this working standard match the δD value of the parent water, and the oxygen isotope values agree within ca. 0.5‰. This indicates that fluid inclusions trapped in calcite at near-ambient temperatures (e.g. speleothems and low-temperatures phreatic calcite) faithfully preserve the original isotopic composition of the parent waters. Copyright © 2009 John Wiley & Sons, Ltd.
A statistical analysis of IRMS and CRDS methods in isotopic ratios of 2H/1H and 18O/16O in water
SN Applied Sciences
Quantitative information about the variation in natural isotopic abundances in water is of great importance in a variety of fields. Due to the wide range of applications and types of samples, it is necessary that isotopic analyses have precision, accuracy and reproducibility. The present study compares the techniques of cavity ring-down spectroscopy (CRDS) and isotope-ratio mass spectrometry (IRMS) for the determination of the isotopic ratios of 2 H/ 1 H and 18 O/ 16 O in water in the two secondary standards, denoted PB3 and PB4, and in a certified material, GISP, Greenland Ice Sheet Precipitation, used as a quality tester of such measurements. The traditional method for measuring isotopic ratios is IRMS. Because of the nature of the molecule, the samples are not introduced directly into the mass spectrometer. Instead, the water is chemically converted to CO 2 and H 2. The other technique, CRDS, is a system of laser absorption that has great potential for the detection of atomic and molecular species with high sensitivity by measuring the light absorption ratio as a function of time, confined within an optical cavity of high finesse. In this technique, the water sample is converted into steam without undergoing conversion processes. Parametric (test T) and nonparametric (Wilcoxon) statistical tests were performed to compare the results obtained in the system, and CRDS and IRMS are from the same population. The values of the isotopic abundances of the two secondary standards [PB3, δD = − 1.9 ± 0.4 (‰) and δ 18 O = − 2.19 ± 0.24 (‰) and PB4, δ 2 H = − 71.4 ± 0.4 (‰) and δ 18 O = − 10.08 ± 0.19 (‰)] were determined with accuracy. For the certified standard GISP, values of δ 2 H = − 189.3 ± 0.5 (‰) and δ 18 O = − 24.69 ± 0.20 (‰) were obtained. Both techniques have factors that interfere with the accuracy of the measurements and require corrections. Comparing the results revealed that there was a greater accuracy for measurements with CRDS and greater precision for IRMS. However, the results are within the tolerance range of 0.2‰ for δ 18 O and 2.0‰ for δ 2 H in isotope hydrology.
Geochemistry, Geophysics, Geosystems
18 O and D of fluid inclusions in carbonates provide insights into temperatures and fluid chemical compositions prevailing during the carbonate precipitation, however various analytical restrictions limit a wider application of this proxy. This paper presents a new fluid inclusions isotopic analytical line coupled to an online cavity ring-down spectrometer that increased the analytical productivity up to ten carbonate samples per working day. This efficiency allowed for the first time to assess the reliability a large set of water samples with size ranging from 0.1 to 1 µL. Good reproducibility (± 0.5 ‰ for 18 O and ± 2 ‰ D; 1) is obtained for water quantity superior or equal to 0.3 L and no evidence of memory effect is found. The line is further tested using two types of natural carbonates: (1) modern speleothems samples from caves for which 18 O and D values of drip water were measured and (2) diagenetic carbonates for which the 18 O of the parent water were independently back-calculated from carbonate clumped isotope 47 measurements. Speleothem fluid inclusion values despite falling close to the Global Meteoritic Water Line are not always representative of the isotopic composition of the parent drip water. Results on diagenetic cements show that the 18 O water values measured in fluid inclusions agree, within 1 %, with the 18 O water independently derived from 47 measurements. Overall, this study confirms the reliability and accuracy of the developed analytical line for carbonate fluid inclusion analyses with a good reproducibility obtained for water quantity above 0.3 L.