Organic residues are extracted from materials of archaeological interest by solvent extraction and subjected directly to high-temperature gas chromatography (GC) and gas chromatographymass spectrometry (GC -MS). The use of hig h-temperature GC allows intact acyl lipids, e.g., triacylglycerols, diacylglycerols, monoacylglycerols and wax esters, to be analysed without prior degradation (e.g., saponification) to release constituent fatty acids and alcohols. Trimethylsilylation is employed to block protic sites in free fatty acids and hydroxylated components. The data obtained from temperature programmed GC and GC -MS analyses, employing im mo bi I ised a pola r (d i met hyl polysi loxane type) stationary phases, provide essentia I compositional information that would be lost if the more conventional degradative approach to acyl lipid analysis was adopted.
Organic residue analysis has heen performed on 62 reconstructed vessels from a single archaeological site ( Raunds, Northamptonshire. U . K . ) . In order to establish regions of lipid accumulation within a vessel, sherds were sampled from different purrs .f' u vessel, ,for e.xample base. body and rim, andsubmitred lo lipidc,.rtractionprocedure.s. The techniques c, f high-temperature gas chromatography (GC) and CClmass spectr0metr.y (GCIMS) were then used to analyse the sherd lipid extracts. The quantitative results obtained show diflerential accumulation and preservation of' lipid in oarious parts of the same vessel. This latter observation has serious implicationsfi,r the sumpling ofpotsherdsfor organic residue analysis. Furthermore, the amount ~fah.sorbed lipid varies quite considerably between vessel types. On this basis. a new method is proposedfor classifying vessel use hy comparing the concentration of lipid present in dijferent parts of individual vessels.
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