Standardization for oxygen isotope ratio measurement - still an unsolved problem

Kornexl, Barbara E.; Werner, Roland A.; Gehre, Matthias

doi:10.1002/(sici)1097-0231(19990715)13:13<1248::aid-rcm560>3.0.co;2-h

Cited by 31 publications

(30 citation statements)

References 33 publications

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“…Recently, Arndt Schimmelmann (Indiana University) has begun making organic standards of known 13 C and 2 H composition available to the research community at nominal cost. No organic O-isotopic standards are available, and standardization for 18 O analyses remains particularly problematic [79]. Most labs currently generate their own standard compounds by calibration using other forms of isotopic analysis, but this leads to obvious concerns about intercalibration between laboratories.…”

Section: Standardizationmentioning

confidence: 99%

Isotope‐ratio detection for gas chromatography

Sessions¹

2006

J of Separation Science

241

270

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Isotope-ratio detection for gas chromatographyInstrumentation and methods exist for highly precise analyses of the stable-isotopic composition of organic compounds separated by GC. The general approach combines a conventional GC, a chemical reaction interface, and a specialized isotoperatio mass spectrometer (IRMS). Most existing GC hardware and methods are amenable to isotope-ratio detection. The interface continuously and quantitatively converts all organic matter, including column bleed, to a common molecular form for isotopic measurement. C and N are analyzed as CO 2 and N 2 , respectively, derived from combustion of analytes. H and O are analyzed as H 2 and CO produced by pyrolysis/reduction. IRMS instruments are optimized to provide intense, highly stable ion beams, with extremely high precision realized via a system of differential measurements in which ion currents for all major isotopologs are simultaneously monitored. Calibration to an internationally recognized scale is achieved through comparison of closely spaced sample and standard peaks. Such systems are capable of measuring 13 C/ 12 C ratios with a precision approaching 0.1? (for values reported in the standard delta notation), four orders of magnitude better than that typically achieved by conventional "organic" mass spectrometers. Detection limits to achieve this level of precision are typically a1 nmol C (roughly 10 ng of a typical hydrocarbon) injected on-column. Achievable precision and detection limits are correspondingly higher for N, O, and H, in that order.

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Section: Standardizationmentioning

confidence: 99%

Isotope‐ratio detection for gas chromatography

Sessions¹

2006

J of Separation Science

241

270

View full text Add to dashboard Cite

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“…The resulting CO 2 was analysed on a VG Isogas SIRA 10 mass spectrometer. Precision and accuracy were monitored by repeat analysis of international standard NBS 127 (8.6 ± 0.4‰, n = 10, accepted value 8.7‰; Kornexl et al 1999).…”

Section: Oxygen and Hydrogen Isotopesmentioning

confidence: 99%

Anomalous alkaline sulphate fluids produced in a magmatic hydrothermal system — Savo, Solomon Islands

et al. 2010

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In magmatic-hydrothermal and associated geothermal systems, acidic magmatic-derived fluids (pH<3) commonly discharge from springs proximal to the vent of active (degassing) volcanoes and more alkaline (pH>5) geothermal fluids are typically limited to lateral outflows some distance from the main vent. Here we describe an unusual hydrothermal system associated with Savo volcano, a recently active (1830-40) trachyte-dominated island arc stratovolcano in the Solomon Islands. Hot springs (~100°C) near to the volcanic crater discharge alkaline waters instead of the more commonly recognised acidic fluids. 2The hydrothermal system of Savo dominantly discharges sinter and travertine-forming alkaline sulphate (pH 7-8) waters at hot springs on its upper flanks, in addition to a small number of lower discharge acid sulphate springs (pH 2-7). Alkaline sulphate springs discharge dilute, chloride-poor (<50 mg/l), sulphate-(>600 mg/l) and silica-rich (>250 mg/l) fluids. They have restricted δ 34 S SO4 (5.4 ± 1.5‰) and δ 18 O H2O values (−4‰; local nonthermal groundwater is −8‰). Acid sulphate springs discharge low chloride (<20 mg/l), high sulphate (300-800 mg/l) waters, with variable silica (100-300 mg/l) and distinctly lower δ 34 S SO4 values (−0.6 ± 2.5‰) compared to the alkaline sulphate fluids. They also display high δ 18 O H2O and δD H2O relative to non-thermal groundwater.Geochemical modelling shows that water-rock reaction and dilution in the presence of secondary anhydrite, pyrite and quartz leads to chloride being diluted to low concentrations, whilst maintaining high sulphate and silica concentrations in the fluid. Strontium, oxygen and hydrogen isotopes confirm water-rock reaction and mixing with groundwater as primary controls on the composition of the alkaline sulphate springs.The highly unusual dilute chemistry of all discharges at Savo is a consequence of high regional rainfall, i.e. climatic control, and results from open system mixing at depth between hydrothermal and meteoric waters.

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“…The d 18 O-value (difference) of both benzoic acid lab standards was confirmed by an independent method (off-line decarboxylation; Santrock and Hayes, 1985) by A. Schimmelmann (Indiana University, Bloomington, USA; Brand, Schimmelmann) (Werner to be published). The standardisation scheme of the carbon reduction measurements (analogous to that described by Kornexl et al, 1999b) included the required SLAP/V-SMOW normalisation (Coplen, 1988), and the measurement strategy and calculation of d 18 Ovalues was analogous to that described by Werner and Brand (2001 …”

Section: O-value Analysis By Irmsmentioning

confidence: 99%