Funding is requested to purchase a gas chromatograph-isotope ratio mass spectrometer (GC-CIRMS). This instrument permits the measurement of carbon and nitrogen stable isotope ratios of a wide variety of organic molecules, essentially all of those which can be resolved by gas chromatography or which can be converted to a suitable volatile derivative. Also, funds are requested for an off-line, automated high-performance liquid chromatography (HPLC) system for isolation of specific compounds for subsequent, off-line, IRMS. This approach is needed for certain compounds which are too involatile or lack sufficient heat stability for GC; it also can be more convenient for compounds, such as amino acids, which require extensive derivatization for GC. Together, these instruments would constitute a facility that could measure the C and N isotopic composition of virtually any organic substance. Specifically, the HPLC and GC-IRMS would be used to measure the stable isotope composition of amino acids and fatty acids in the course of studies of the growth rate and trophic dynamics of marine mammals. The stable isotope composition of specific organic compounds, such as amino acids, carbohydrates, hydrocarbons, and lipids, from marine and lake sediments would be used in investigations of the sources and diagenetic alteration of these substances, assisting studies of environmental change at high northern latitudes. Also, the instruments would be used in tracer investigations of the metabolism of large mammals by measuring changes over time in the isotopic composition of metabolites such as volatile fatty acids. Finally, the GC-C-IRMS would be used to distinguish naturally-occurring hydrocarbons from petroleum-derived contaminants.
