STABLE CARBON ISOTOPIC ANALYSES OF LIGNIN-DERIVED CUO OXIDATION-PRODUCTS BY ISOTOPE RATIO MONITORING GAS CHROMATOGRAPBY MASS-SPECTROMETRY (IRM-GC-MS)

In this paper, we evaluate compound-specific isotope analyses of ligni n reaction products through the combined application of alkaline CuO o xidation and isotope ratio monitoring-gas chromatography-mass spectrom etry (irm-GC-MS). Analyses of phenol standards as trimethylsilyl ether s/esters by irm-GC-MS yield accurate (+/-0.5 parts per thousand) estim ates of their isotopic signatures after correcting for added derivativ e carbon with precisions greater than or equal to 1 parts per thousand CuO oxidation of purified lignin polymers yields reaction products th at retain the isotopic composition of their polymeric precursors (with in +/-1 parts per thousand). Analyses of a variety of vascular plant t issues reveal important differences in the isotopic compositions of li gnin phenols from C-3 (average of all compounds = -30.4 parts per thou sand +/- 3.9 parts per thousand) and C-4 (-16.9 +/- 2.7 parts per thou sand) plants. These differences are apparent in organic matter concent rates from several sediments and can be used to estimate the principal sources of lignin and vascular plant remains in a variety bf settings . Finally, comparative analyses of bulk sediment and organic matter co ncentrate from the same sample show that it is possible to characteriz e directly the isotopic composition of sedimentary lignins by combined application of alkaline CuO oxidation and irm-GC-MS without the need for prior demineralization. Copyright (C) 1996 Elsevier Science Ltd