Dual-inlet Isotope Ratio Mass Spectrometer Research Articles

Application of environmental isotopes and hydrochemistry in the identification of source of seepage and likely connection with lake water in Lesser Himalaya, Uttarakhand, India

Oxygen (\({\updelta }^{18}\hbox {O}\)) and hydrogen (\({\updelta }^{2}\hbox {H}\) and \(^{3}\hbox {H}\)) isotopes of water, along with their hydrochemistry, were used to identify the source of a newly emerged seepage water in the downstream of Lake Nainital, located in the Lesser Himalayan region of Uttarakhand, India. A total of 57 samples of water from 19 different sites, in and around the seepage site, were collected. Samples were analysed for chemical tracers like \(\hbox {Ca}^{++}\), \(\hbox {Mg}^{++}\), \(\hbox {Na}^{+}\), \(\hbox {K}^{+}\), \({\hbox {SO}_{4}}^{--}\) and \(\hbox {Cl}^{-}\) using an Ion Chromatograph (Dionex IC-5000). A Dual Inlet Isotope Ratio Mass Spectrometer (DIIRMS) and an Ultra-Low Level Liquid Scintillation Counter (ULLSC), were used in measurements of stable isotopes (\({\updelta }^{2}\hbox {H}\) and \({\updelta }^{18}\hbox {O}\)) and a radioisotope (\(^{3}\hbox {H}\)), respectively. Results obtained in this study repudiate the possibility of any likely connection between seepage water and the lake water, and indicate that the source of seepage water is mainly due to locally recharged groundwater. The study suggests that environmental isotopes (\({\updelta }^{2}\hbox {H}\), \({\updelta }^{18}\hbox {O}\) and \(^{3}\hbox {H}\)) can effectively be used as ‘tracers’ in the detection of the source of seepage water in conjunction with other hydrochemical tracers, and can help in water resource management and planning.

Rapid and high-resolution stable isotopic measurement of biogenic accretionary carbonate using an online CO2 laser ablation system: Standardization of the analytical protocol.

The elaborate sampling and analytical protocol associated with conventional dual-inlet isotope ratio mass spectrometry has long hindered high-resolution climate studies from biogenic accretionary carbonates. Laser-based on-line systems, in comparison, produce rapid data, but suffer from unresolvable matrix effects. It is, therefore, necessary to resolve these matrix effects to take advantage of the automated laser-based method. Two marine bivalve shells (one aragonite and one calcite) and one fish otolith (aragonite) were first analysed using a CO2 laser ablation system attached to a continuous flow isotope ratio mass spectrometer under different experimental conditions (different laser power, sample untreated vs vacuum roasted). The shells and the otolith were then micro-drilled and the isotopic compositions of the powders were measured in a dual-inlet isotope ratio mass spectrometer following the conventional acid digestion method. The vacuum-roasted samples (both aragonite and calcite) produced mean isotopic ratios (with a reproducibility of ±0.2 ‰ for both δ18 O and δ13 C values) almost identical to the values obtained using the conventional acid digestion method. As the isotopic ratio of the acid digested samples fall within the analytical precision (±0.2 ‰) of the laser ablation system, this suggests the usefulness of the method for studying the biogenic accretionary carbonate matrix. When using laser-based continuous flow isotope ratio mass spectrometry for the high-resolution isotopic measurements of biogenic carbonates, the employment of a vacuum-roasting step will reduce the matrix effect. This method will be of immense help to geologists and sclerochronologists in exploring short-term changes in climatic parameters (e.g. seasonality) in geological times.

Improved analysis of micro- and nanomole-scale sulfur multi-isotope compositions by gas source isotope ratio mass spectrometry.

Multiple sulfur isotope compositions are usually measured on relatively large samples (in the range of micromoles); however, sometimes only small amounts are available and thus it is necessary to analyze small (sub-micromole) samples. We report an improved method to measure multiple sulfur isotope compositions: δ(33) S, δ(34) S and δ(36) S values on the SF6 molecule (m/z 127, 128, 129, 131) for quantities down to 0.1 micromole, and δ(33) S and δ(34) S values for quantities down to 20 nanomoles. Multiple sulfur isotope analyses including fluorination and purification of two international Ag2 S standards, IAEA-S1 and IAEA-S3, were carried out at various low concentrations on a dual-inlet isotope ratio mass spectrometer using a microvolume and modified resistor capacities. The analyses yielded a narrow range of δ(34) S values vs CDT (the international standard), with an overall standard deviation of ±0.2 ‰, which was within the range of certified values. This demonstrates the feasibility of determining both Δ(33) S and Δ(36) S values on the sub-micromole scale, and Δ(33) S values on the nanomole scale with similar accuracy to conventional dual-inlet analyses. The analysis of the three S-isotope ratios on the SF6 molecule using the so-called conventional fluorination method and dual-inlet ion ratio mass spectrometry is reliable for sample sizes down to ~20 nanomoles. Despite being close to the theoretical limits for maintaining the viscous flow regime of gas in the capillary, errors were not limited by counting statistics, but probably relate to sample gas purification. Copyright © 2016 John Wiley & Sons, Ltd.

Influence of dissolved ions on determination of oxygen isotope composition of aqueous solutions using the CO2‐H2O equilibration method

Stable isotope compositions of natural waters, such as seawater, glaciers and basinal brines, can provide valuable information about Earth's hydrological cycle and its evolutionary history. However, a high concentration of dissolved ions in some natural waters hinders an accurate analysis of their oxygen isotope composition. A laboratory study was carried out in order to provide guidelines on how to resolve this analytical difficulty. CO(2) gas was equilibrated with saline aqueous solutions of various chemical compositions at 25 °C. Subsequently, the oxygen isotope composition of the CO(2) was determined at different equilibration times using a dual-inlet isotope ratio mass spectrometer in order to evaluate the oxygen isotope salt effect and the rate of oxygen isotope exchange between CO(2) and the saline solution. Using the experimentally determined oxygen isotope salt effects of aqueous chloride and sulfate solutions, an empirical method for the prediction of the oxygen isotope salt effect of a 1.0 molal chloride or sulfate solution was proposed. The rates of oxygen isotope exchange between CO(2) and saline solutions were also examined. Our experimental data indicates that the sequence of the oxygen isotope exchange time is as: MgSO(4) > CaCl(2) ≈ Na(2)SO(4) > NaCl > MgCl(2) > KCl > H(2)O. The isotope salt effect and the kinetics of isotope exchange must be taken into account when the oxygen isotope composition of a saline aqueous solution is determined using the CO(2)-H(2)O equilibration method. Our experimental data and the proposed prediction method provide essential guidelines for the accurate δ(18)O analysis of saline aqueous solutions.

Mass-dependent fractionation of quadruple stable sulfur isotope system as a new tracer of sulfur biogeochemical cycles

Sulfur isotope studies of post-Archean terrestrial materials have focused on the ratio 34S/ 32S because additional isotopes, 33S and 36S, were thought to carry little information beyond the well-known mass-dependent relationship among multiple-isotope ratios. We report high-precision analyses of Δ 33S and Δ 36S values, defined as deviations of 33S and 36S from ideal mass-dependent relationships, for international reference materials and sedimentary sulfides of Phanerozoic age by using a fluorination technique with a dual-inlet isotope ratio mass spectrometer. Measured variations in Δ 33S and Δ 36S are explained as resulting from processes involve branching reactions (two or more reservoirs formed) or mixing. Irreversible processes in closed systems (Rayleigh distillation) amplify the isotope effect. We outline how this new isotope proxy can be used to gain new insights into fundamental aspects of the sulfur biogeochemical cycle, including additional constraints on seawater sulfate budget and processes in sedimentary sulfide formation. The isotope systematics discussed here cannot explain the much larger variation of Δ 33S and Δ 36S observed in Archean rock records. Furthermore, Phanerozoic samples we have studied show a characteristic Δ 33S and Δ 36S relationship that differs from those measured in Archean rocks and laboratory photolysis experiments. Thus, high precision analysis of Δ 33S and Δ 36S can be used to distinguish small non-zero Δ 33S and Δ 36S produced by mass-dependent processes from those produced by mass-independent processes in Archean rocks and extraterrestrial materials.

A robust and fast method of sampling and analysis of δ13C of dissolved inorganic carbon in ground waters

The stable carbon isotopic composition of dissolved inorganic carbon (δ13CDIC) is traditionally determined using either direct precipitation or gas evolution methods in conjunction with offline gas preparation and measurement in a dual-inlet isotope ratio mass spectrometer. A gas evolution method based on continuous-flow technology is described here, which is easy to use and robust. Water samples (100–1500 μl depending on the carbonate alkalinity) are injected into He-filled autosampler vials in the field and analysed on an automated continuous-flow gas preparation system interfaced to an isotope ratio mass spectrometer. Sample analysis time including online preparation is 10 min and overall precision is 0.1 ‰. This method is thus fast and can easily be automated for handling large sample batches.

The determination of [formula omitted] in soil microbial biomass using fumigation-extraction

The determination of the isotopic composition of the microbial biomass C in soil is an important tool to study soil microbial ecology and the decomposition and microbial immobilization of soil organic C. We discuss advantages and disadvantages of different methods to determine 13C/ 12C in soil microbial biomass and propose a new procedure that is based on the UV-catalyzed liquid oxidation of fumigated and non-fumigated soil extracts combined with trapping of the released CO 2 in liquid nitrogen and subsequent determination of δ 13 CO 2 -C by a gas chromatograph connected with an isotope ratio mass spectrometer (IRMS). This method was evaluated using test solutions with known isotopic composition and soil extracts. Additionally, the method was compared with an off-line sample preparation technique combined with isotope analysis by a dual-inlet IRMS and an on-line analysis using an elemental analyser connected with an IRMS. All methods applied obtained comparable results and there were no significant differences between the δ 13 C values measured. The off-line preparation procedure had the highest precision but it was also the most labour-intensive. The choice of the most suitable method depends mainly on the number of samples that have to be analysed, the salt concentration of the extracts and the differences of δ 13 C that have to be detected. The application of this method with liquid oxidation and subsequent GC-IRMS analysis showed that microbial biomass C of a grassland soil was 13C-enriched by 2‰ δ 13 C PDB compared with the total soil organic C. The addition of maize straw resulted in a rapid immobilization of maize C in the microbial biomass.

Hydrogen isotope analysis of natural abundance and deuterium-enriched waters by reduction over chromium on-line to a dynamic dual inlet isotope-ratio mass spectrometer.

This paper describes the application of a simple chromium reduction furnace which can be interfaced with a dual inlet isotope-ratio mass spectrometer thus providing the capacity for cheap, fast, accurate and precise measurement of deltaD(V-SMOW) by dynamic mass spectrometry. Measurements are precise to the order of < or =0.5 per thousand. Mean 95% confidence intervals for the Vienna Standard Mean Ocean Water (V-SMOW) to Standard Light Antarctic Precipitation (SLAP) range are in the order of 2.5 per thousand and the system is linear over the range -428 to 23,000 per thousand. Memory effects do exist, but are small for natural abundance samples and can be minimised by careful planning of the analytical load.

High precision and spatial resolution sulfur isotope analysis using MILES laser microprobe

The MILES ( Micro In situ Laser Extraction System) laser microprobe permits high spatial resolution (< 10 −3mm 3, or < 0.2 μmol S) in situ sampling of geological material for sulfur isotope analysis. Sulfides are combusted in F 2 by absorption of CO 2 laser radiation and converted to sulfur hexafluoride (SF 6). The product SF 6 is purified by cryogenic distillation. In combination with a high-sensitivity dualinlet isotope ratio mass spectrometer, sulfur isotope analyses of powders of pyrite, galena, and sphalerite yield δ 34S cdt values with a high precision, ranging from 0.03 to 0.09%. The sulfur isotope ratios measured are accurate and exhibit no matrix-dependent sulfur isotope effects over the range of 62%. A minimum F 2 pressure of 20 kPa (for MILES) is required to mediate against small isotopic fractionations between multiple sulfur species apparently caused by laser isotope separation and/or reaction with oxygen during analysis. The precision and accuracy of δ 34S cdt values from in situ analyses are good ( $ ̌ 0.2‰), but isotopically homogeneous working standards or intercomparison materials are not available thus far. Sulfur isotope ratios derived by conventional-SO 2 and laser-SF 6 are well correlated ( r 2 = 0.99999), but a slope different from unity ( m = 1.035) arises, probably due to inadequate corrections to SO 2 data for oxygen isobaric interferences. Sulfur isotope isopleths in a large, cubic metamorphic pyrite porphyroblast, determined from 79 in situ analyses, are discordant to crystallographic zonation. Concordance between crystallographic and isotopic zonation needs be tested using high precision and spatial resolution analyses such as those described here. Sampling crystallographic zones in minerals can result in erroneous conclusions if isotopic and crystallographic zoning are not coincident.

A Rapid 13C/12C Test for Determination of Corn Syrups in Honey

Abstract The AOAC official method for detection of corn syrup products in honey measures the 13C/12C ratio (δ13C) (978.17). In the official method, a suspect honey is combusted off-line to C02 gas for analysis on a dual-inlet isotope ratio mass spectrometer (IRMS). The procedure is manual, requires liquid N2, and takes 20-50 min/sample. In the present study, we examine a recently developed alternative, automated 15N 13C analysis mass spectrometry (ANCA-MS). This procedure combusts and analyzes 66 samples in a batch and takes only 5 min/sample. We used both ANCA-MS and IRMS with offline combustion to analyze 6 honeys containing from 0 to 100% high fructose corn syrup (HFCS). δ13C values by both methods agreed within 0.2%o and gave an excellent straight line fit (slope = 0.991; R = 1). As an alternative to IRMS, ANCA-MS is automated and provides a 5-fold increase in sample throughput.