title: Optimization of on-line hydrogen stable isotope ratio measurements of halogen- and sulfur-bearing organic compounds using elemental analyzer-chromium/high-temperature conversion isotope ratio mass spectrometry (EA-Cr/HTC-IRMS).
abstract: BACKGROUND
  Accurate hydrogen isotopic analysis of halogen- and sulfur-bearing organics has not been possible with traditional high-temperature conversion (HTC) because the formation of hydrogen-bearing reaction products other than molecular hydrogen (H2) is responsible for non-quantitative H2yields and possible hydrogen isotopic fractionation. Our previously introduced, new chromium-based EA-Cr/HTC-IRMS (Elemental Analyzer-Chromium/High-Temperature Conversion Isotope Ratio Mass Spectrometry) technique focused primarily on nitrogen-bearing compounds. Several technical and analytical issues concerning halogen- and sulfur-bearing samples, however, remained unresolved and required further refinement of the reactor systems.
  
  
  METHODS
  The EA-Cr/HTC reactor was substantially modified for the conversion of halogen- and sulfur-bearing samples. The performance of the novel conversion setup for solid and liquid samples was monitored and optimized using a simultaneously operating dual-detection system of IRMS and ion trap MS. The method with several variants in the reactor, including the addition of manganese metal chips, was evaluated in three laboratories using EA-Cr/HTC-IRMS (on-line method) and compared with traditional uranium-reduction-based conversion combined with manual dual-inlet IRMS analysis (off-line method) in one laboratory.
  
  
  RESULTS
  The modified EA-Cr/HTC reactor setup showed an overall H2-recovery of more than 96% for all halogen- and sulfur-bearing organic compounds. All results were successfully normalized via two-point calibration with VSMOW-SLAP reference waters. Precise and accurate hydrogen isotopic analysis was achieved for a variety of organics containing F-, Cl-, Br-, I-, and S-bearing heteroelements. The robust nature of the on-line EA-Cr/HTC technique was demonstrated by a series of 196 consecutive measurements with a single reactor filling.
  
  
  CONCLUSIONS
  The optimized EA-Cr/HTC reactor design can be implemented in existing analytical equipment using commercially available material and is universally applicable for both heteroelement-bearing and heteroelement-free organic-compound classes. The sensitivity and simplicity of the on-line EA-Cr/HTC-IRMS technique provide a much needed tool for routine hydrogen-isotope source tracing of organic contaminants in the environment. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Department for Isotope Biogeochemistry, Helmholtz-Centre for Environmental Research (UFZ), Permoserstrasse 15, D-04318, Leipzig, Germany.
authors.forename: Matthias
authors.identifier: http://orcid.org/0000-0001-7177-0422
authors.initials: M
authors.lastname: Gehre
authors.affiliation: Department for Isotope Biogeochemistry, Helmholtz-Centre for Environmental Research (UFZ), Permoserstrasse 15, D-04318, Leipzig, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Renpenning
authors.affiliation: Max-Planck-Institute for Biogeochemistry, Beutenberg Campus, P.O. Box 100164, D-07701, Jena, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Geilmann
authors.affiliation: U.S. Geological Survey, 431 National Center, Reston, VA, 20192, USA.
authors.forename: Haiping
authors.initials: H
authors.lastname: Qi
authors.affiliation: U.S. Geological Survey, 431 National Center, Reston, VA, 20192, USA.
authors.forename: Tyler B
authors.initials: TB
authors.lastname: Coplen
authors.affiliation: Department for Isotope Biogeochemistry, Helmholtz-Centre for Environmental Research (UFZ), Permoserstrasse 15, D-04318, Leipzig, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Kümmel
authors.affiliation: Department for Isotope Biogeochemistry, Helmholtz-Centre for Environmental Research (UFZ), Permoserstrasse 15, D-04318, Leipzig, Germany.|Isodetect GmbH, Deutscher Platz 5b, D-04103, Leipzig, Germany.
authors.forename: Natalija
authors.initials: N
authors.lastname: Ivdra
authors.affiliation: Max-Planck-Institute for Biogeochemistry, Beutenberg Campus, P.O. Box 100164, D-07701, Jena, Germany.
authors.forename: Willi A
authors.initials: WA
authors.lastname: Brand
authors.affiliation: Department of Geological Sciences, Indiana University, Bloomington, IN, 47405-1405, USA.
authors.forename: Arndt
authors.initials: A
authors.lastname: Schimmelmann