Characterising native plant resins from Australian Aboriginal artefacts using ATR-FTIR and GC/MS

Abstract

Resin use by Australian Aborigines has been documented in ethnographic accounts across the continent and is also evident from archaeological and anthropological artefacts. This research assesses the use of attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and gas chromatography coupled mass spectrometry (GC/MS) for the identification of native plant resins on museum artefacts. A collection of thirteen museum artefacts were analysed using light microscopy and characterised using both ATR-FTIR and GC/MS. The resins were identified to the plant genus and one to the species level, as spinifex (Triodia spp. R.Br.), ironwood (Erythrophleum chlorostachys (F. Muell.) Baill.) and grass tree (Xanthorrhoea spp. Sm.) by comparison to a reference collection of modern exudates from 34 Australian plant species. The two analytical methods used, produced a significant agreement in results but one has practical advantages. On eight of the artefacts, ATR-FTIR was able to be performed on the residue in situ, without removal, presenting a non-destructive analytical method for the identification of resins which is applicable to rare and delicate artefacts from museum collections. Permission to remove the residue off the artefact is not always granted or feasible, so ATR-FTIR has a significant advantage over GC/MS and other methods which require chemical treatment or even destruction of the archaeological sample. Both of the methods examined are demonstrated to accurately infer the botanical origin of archaeological and anthropological resins, providing insight on the use, preparation and trading of resins, with the consequent contribution to an understanding of the development and use of hafted tools and other aspects of cultural development.