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 H2
yields 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.
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.
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.