The use of CuO oxidation in combination with isotope ratio monitoring GC-MS to characterize lignins from vascular plant tissues and sedimentary samples

A variety of phenolic standards were analyzed as trimethylsilyl derivatives by irm-GC-MS and their {gamma}{sup 13}C values (after correcting for derivative carbons) found to be within 1{per_thousand} of the isotopic compositions determined by off-line combustion. CuO oxidation products from several isolated lignins were analyzed by irm-GC-MS and their {gamma}{sup 13}C values determined to be representative of the isotopic composition of their respective polymeric precursors. Oxidation of several plant tissues from both C{sub 3} and C{sub 4} showed clear distinctions in the lignin isotopic signatures of these two plant types, consistent with their bulk {gamma}{sup 13}C{sub TOC}. In some cases, we observed differences in the isotopic composition of individual classes of lignin oxidation products that might reflect their biosynthetic pathway. Various woods degraded under laboratory conditions were analyzed and the {gamma}{sup 13}C values of the individual lignin products determined in order to assess the effects of degradation on their isotopic signatures. Several riverine, estuarine and marine sediments were analyzed in a similar manner and the isotopic signatures of individual lignin-derived phenols used to trace the predominant lignin sources.