Clara Azemard

Analysis of diterpenic compounds by GC-MS/MS: contribution to the identification of main conifer resins

AbstractThe three principal types of molecules composing diterpenic resins are the abietanes, pimaranes and labdanes. The study of their fragmentation was performed by gas chromatography coupled to an ion trap mass spectrometer, on standards and resins used in paint varnishes: colophony and sandarac. We found that the general fragmentation pattern was mostly governed by the location of the double bonds on the different cycles and the presence of functional groups, and not by the nature of the C13 group in the case of abietanes and pimaranes. As for the labdanes, the loss of their alkyl chain is very specific. This study develops an analytical strategy using tandem mass spectrometry (MS/MS) experiments to validate the proposed mechanisms of fragmentation and to find the ions of interest for the identification of diterpenic molecules. Graphical AbstractAnalysis of diterpenic compounds by GC-MS/MS

Geochemical Characterization of Lapita Ceramics From the Western Solomon Islands by Means of Portable X-Ray Fluorescence and Scanning Electron Microscopy

ABSTRACT The study of interaction and exchange among different geographic areas in the Western Pacific occupied by Lapita people (3500–2500 BP) has been an important component of research into the colonization process of the Pacific region. The Western Solomon Islands, lying in the central area of the Lapita distribution, have a unique archaeological record presenting intertidal sites with Late/Post Lapita ceramics as the only material evidence of Lapita occupation. Previous studies have indicated that Lapita ceramic production was mainly local. However, temper analysis has identified exotic ceramics in Late Lapita sites in the New Georgia Group, indicating complex ceramic transfer including from outside the Solomon Islands region. Analysis of Late Roviana (New Georgia) and historic period ceramic sherd temper has also suggested ceramic transfer from the nearby island of Choiseul, where ceramics were manufactured until recent times. Here we present results of a series of portable X-ray fluorescence and Scanning Electron Microscopy analyses carried out on ceramic pastes from the New Georgia group in the Western Solomon Islands. These results confirm that during the Early (Lapita/Post Lapita) ceramic period, production was present at multiple locations and that ceramics were transferred at different geographic scales involving occasional long-distance interactions. During the later period (AD 1400–1900) ceramic production had a more restricted occurrence with transfer networks changing and receding to become exclusively regional.