APPLICATION OF ISOTOPE RATIO MONITORING GAS-CHROMATOGRAPHY MASS-SPECTROMETRY TO THE ANALYSIS OF ORGANIC RESIDUES OF ARCHAEOLOGICAL ORIGIN

Isotope ratio monitoring gas chromatography-mass spectrometry (irm GC- MS) was used to determine the delta C-13 values of individual compound s present in organic residues preserved in archaeological potsherds. T he lipid fractions of the preserved organic residues were extracted fr om potsherds recovered from excavations performed as part of the Raund s Area Project, Northamptonshire, UK. The lipid extracts were analysed by high temperature GC and GC-MS. The leaf wax of a contemporary wild -type Brassica was also extracted and analysed for comparative purpose s. Prior to irm GC-MS analysis, lipid extracts were fractionated; alka ne and ketone fractions were obtained from the wild-type Brassica leaf wax, the total lipid extracts of two of the potsherds, and an archaeo logical soil sample using small- scale flash chromatography. The delta C-13 values obtained for the samples were consistent with the individ ual lipids investigated being of C-3 plant origin. These data support the hypothesis that the lipids preserved in the potsherds were derived from a Brassica species such as cabbage. These results confirm the po tential value of irm GC-MS to derive stable isotope ratios for individ ual lipid species of archaeological interest, and, more specifically, the potential for application of the technique to palaeodietary invest igations.