Compound-specific stable hydrogen isotope analysis of natural samples in nano-molar levels and its application to earth environmental sciences

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Compound-specific hydrogen isotope measurement has been developed at sub-nano molar level using gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC/pyrolysis/IRMS). Isotopic calibration and sample preparation including derivatization of unvolatile compounds and separation of co-eluted compounds by silica gel chromatography were also established for more precise isotope measurement. Finally, it is successful to determine a OD value of natural samples with precision of less than 5‰ using ・0ng hydrogen-containing organic compound. We applied the established method to determine δD values of n-alkanes, n-alkanoic acids, n-alkanols and sterols of biological materials and sediments, in order to discuss their isotope fractionation mechanisms during different biosynthetic pathways as well as their source, diagenetic effects and transportation processes in sediments. We also conducted the δD measurement of polycyclic aromatic hydrocarbons such as pyrene and fluoranthene in carbonaceous chondrites to find different the δD value in spite of their structural isomers each other (C_<16>H_<10>). In addition, hydrogen isotope exchange of pyrene and fluoranthene occurred in hydrothermal solutions under acidic condition, where where hydrogens have exchanged more easily between pyrene and water relative to between fluoranthene and water. The kinetically different behavior between pyrene and fluoranthene coincides with the two-series (pyrene-series and fluoranthene-series) PAH formation mechanisms in carbonaceous chondrites inferred from carbon isotopic compositions of PAH.Originally this reserch project was planned for 4 years (2000-2003 FY). However, since this project has successfully continued to a new research project as titled "Multi-stable isotope systematics of individual organic compounds in cosmogeochemical samples", this project ended up to make a final report.