Gas chromatograph/pyrolysis/isotope ratio mass spectrometer (GC/pyrolysis/IRMS) and pyrolysis elemental analyzer/isotope ratio mass spectrometer (pyrolysis-EA/IRMS) are relatively new instruments for on-line determination of stable hydrogen isotopic composition (D/H) of organic compounds, which allow easy and rapid access to their isotopic composition in various biological and geological samples. The hydrogen isotopic composition is a potential tool for the reconstruction of hydrological cycle in paleoenvironment. Combined with carbon isotopic composition (¹³C/¹²C), it has also been used for the evaluation of sources and delivery of organic compounds in geological as well as geographical samples. This paper reviews recent studies on the compound-specific hydrogen isotope analysis of lipids and pigments, which consists of brief summaries of (1) biological controls on the isotopic composition, (2) isotopic modification associated with biodegradation and diagenesis, and (3) its application in organic geochemistry.

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Diamondoid hydrocarbons have been identified in Toarcian black shale alternated with bedded chert from Unuma-Hosekiji, Gihu, central Japan. The thickness of the black shale was 60cm, and seven samples were collected vertically. 73 adamantanes, 21 diamantanes and 6 triamantanes were identified in this black shale. Five diamondoid hydrocarbon ratios have been used as maturity and source rock parameter to compare each sample. These parameters indicate that the maturity levels of the black shale were increased with depth, and the influence of marine and carbonate source material were also increased with depth, although all samples were expected to indicate same values. The reason of the change of parameters is not clear, but the causes seem to be (1) the difference of contents of catalysis such as clay minerals and zeolites, (2) the migration of organic matter from radiolarian mud during early diagenesis, (3) the change of oxic/anoxic environment during the black shale accumulation.

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The chemical compositions of woody fossil fragments collected by picking manually and density centrifugation from sandstones of the Lower Cretaceous Yezo Group in Oyubari, central Hokkaido, Japan were analyzed by KOH/methanol hydrolysis (saponification) after solvent extraction. Organic compounds bound in macromolecules of the woody fragments with ester bonds, obtained by saponification, were mainly composed of short-chain (C₁₄ to C₁₈) fatty acids and series of n-alkanols ranging from C₁₂ to C₂₈ homologues. These ester bound constituents are attributed to moieties of polyester parts of selectively preserved resistant macromolecule like cutin or suberin. Even carbon-number predominance was observed in both compounds, which indicated that biological components were well preserved. The bound fatty acids showed similar distribution patterns among all samples, indicating that these moieties might have been altered by strong diagenetic processes. On the other hand, the distribution patterns of n-alkanols significantly varied. In particular, those of long-chain (>C₂₀) n-alkanols varied possibly depending on plant taxonomy. Thus, we suggest that these parameters are strongly useful as molecular paleobiological indicators for chemotaxonomic analyses. Also, the distributions of short-chain n-alkanols and the ratios of short to long-chain homologues are presumably useful indicators for diagenesis, taphonomy and environment.

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