Extraction and derivatization of absorbed lipid residues from very small and very old samples of ceramic potsherds for molecular analysis by gas chromatography–mass spectrometry (GC–MS) and single compound stable carbon isotope analysis by gas chromatography–combustion–isotope ratio mass spectrometry (GC–C–IRMS)

Abstract

Lipid residue analysis has become a common technique for the identification of the organic residues remaining from resources processed in archaeological ceramic vessels. However, recovery of lipids from the vessels can be problematic in cases of high age and/or very small sample amounts. Here we show that acid-catalyzed direct extraction and methylation offers an efficient way to obtain enough fatty acids for quantification and stable carbon isotope analysis. We compared this technique with the more conventional technique of ultrasonically aided solvent extraction followed by silylation, which gave no measurable yields. Both techniques were applied on the absorbed residues of six extremely small sample amounts of less than 0.1g of ceramic powder each from the Sankakuyama I site, Kyushu, South Japan (~13,900–13,300calBP). They belong to one of the oldest so far reported pottery traditions in the world, the Japanese Incipient Jōmon. δ13C analysis of the identified target C16:0 and C18:0 fatty acids indicated that the examined vessels were used for food-processing purposes, pointing to a significant contribution of terrestrial animal sources in the residues.