The use of GCMS and LCMS is a long-established and valuable technique for the determination of biomarkers in the archaeological record. Natural plant exudates are of particular interest as identification of the organic compounds present in these resinous materials permits conclusions to be drawn as to their origin. Such information relating to the botanical and geographical source of these highly valued aromatic substances has enabled the extent of ancient trade networks and cultural influences to be evaluated. For example, the analysis of organic residues recovered from burial contexts in Britain has shed light on the long-distance transport of resins for use as part of mortuary rites in the Roman period.Robust ways of differentiating between the often structurally similar compounds present in such plant exudates is therefore important. Two such compounds are the isomeric triterpenes oleanolic acid (1) and ursolic acid (3). Analysis of these triterpenes is further complicated by the fact that both compounds can be found in nature as either their 3α (2 and 4) or 3β epimers. This presentation will discuss the use of positive mode APCI for the differentiation of stereoisomers of compounds of this type. The fragmentation of the protonated molecule varies systematically with stereochemistry, with the secondary fragmentation of the [MH-H2O]+ offering conformatory evidence for the stereochemistry. The mechanism of these divergent fragmentations will be analysed.

Positive mode atmospheric pressure chemical ionisation mass spectrometry in archaeological analyis: Differentiation of epimers of pentacyclic terpenoids

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.