Original paper

Fresenius' Journal of Analytical Chemistry

, Volume 370, Issue 4, pp 358-362

An interlaboratory study to test instrument performance of hydrogen dual-inlet isotope-ratio mass spectrometers

  • W. A. BrandAffiliated withMax-Planck-Institute for Biogeochemistry, P.O. Box 100164, 07701 Jena, Germany
  • , T. B. CoplenAffiliated withU.S. Geological Survey, 431 National Center, Reston, VA 20192, USA e-mail: tbcoplen@usgs.gov

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Abstract

An interlaboratory comparison of forty isotope-ratio mass spectrometers of different ages from several vendors has been performed to test 2H/1H performance with hydrogen gases of three different isotopic compositions. The isotope-ratio results (unsufficiently corrected for H3 + contribution to the m/z = 3 collector, uncorrected for valve leakage in the change-over valves, etc.) expressed relative to one of these three gases covered a wide range of values: –630‰ to –790‰ for the second gas and –368‰ to –462‰ for the third gas. After normalizing the isotopic abundances of these test gases (linearly adjusting the δ values so that the gases with the lowest and highest 2H content were identical for all laboratories), the standard deviation of the 40 measurements of the intermediate gas was a remarkably low 0.85‰. It is concluded that the use of scaling factors is mandatory for providing accurate internationally comparable isotope-abundance values. Linear scaling for the isotope-ratio scales of gaseous hydrogen mass spectrometers is completely adequate.