Isotope-ratio-monitoring gas chromatography methods for high-precision isotopic analysis of nanomole quantities of silicate nitrogen

Gray Edward Bebout, Bruce D. Idleman, Long Li, Andreas Hilkert

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

We have developed a system for analyzing nanomole-sized quantities of silicate-derived N2 by carrier-gas methods, through combination of a metal high-vacuum extraction line fabricated at Lehigh University and a commercially available continuous-flow, gas chromatography interface (the Finnigan Gas Bench II). This work involves heating of samples to 950-1050 °C (depending on the material being analyzed), with Cu metal and Cu oxide reagents, in evacuated and sealed 6 mm (o.d.) quartz tubes. Uncertainties (expressed as 1σ for ≥ 3 replicate analyses of both internal silicate standards and unknowns) are generally less than 5% for N concentrations and on the order of 0.15‰ δ15N for samples with > 5 ppm N. At current blank levels (minimum overall system blank of 3.8 ± 0.2 nmol N2 with a δ15Nair value of - 7.3 ± 0.4‰, mean ± 1σ), uncertainty in δ15N increases to ∼ 0.6‰ for samples with 1-2 ppm N. Practical minimum sample size, taking into account blanks and other factors affecting N2 transfer, is now ∼ 10 nmol, two orders of magnitude smaller than that previously possible in our laboratory using dual-inlet microvolume methods (∼ 1 μmol). These methods, which can be employed in any laboratory able to undertake continuous flow techniques (with a dynamic-vacuum, isotope ratio mass spectrometer), afford increased spatial resolution in some studies and open up many new avenues of investigation previously impeded by the absence of sufficiently N-rich materials.

Original languageEnglish
Pages (from-to)1-10
Number of pages10
JournalChemical Geology
Volume240
Issue number1-2
DOIs
Publication statusPublished - May 15 2007
Externally publishedYes

Fingerprint

Silicates
isotopic analysis
Isotopes
Gas chromatography
gas chromatography
Nitrogen
silicate
Gases
Metals
Vacuum
isotope
Quartz
Monitoring
nitrogen
Mass spectrometers
monitoring
Oxides
metal
Heating
gas

Keywords

  • Carrier gas
  • Mass spectrometry
  • Nitrogen isotopes
  • Oceanic basalt

ASJC Scopus subject areas

  • Geology
  • Geochemistry and Petrology

Cite this

Isotope-ratio-monitoring gas chromatography methods for high-precision isotopic analysis of nanomole quantities of silicate nitrogen. / Edward Bebout, Gray; Idleman, Bruce D.; Li, Long; Hilkert, Andreas.

In: Chemical Geology, Vol. 240, No. 1-2, 15.05.2007, p. 1-10.

Research output: Contribution to journalArticle

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