Ageing characterization and origin traceability of archaeological amber artefacts via FTIR spectroscopy and pyrolysis-gas chromatography/mass spectrometry

The archaeological amber artefacts from various periods in China provide valuable insights into ancient international trade and cultural interactions. This study investigated several archaeological amber artefacts (Arc 1–6) from the collection of the Hunan Museum, originating from different historical periods. The examination of the ageing characteristics of the cross-section and weathered surface was carried out using scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy and Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) to analyse the functional groups and chemical compositions. FTIR spectroscopy proved limited information in determining the origin due to natural ageing causing alterations in peak shape/position or signal noise. Py-GC/MS analysis identified the amber artefacts as succinite and revealed that a set of compounds can serve as markers for identifying the origin. The pyrogram patterns classified the samples into two groups based on the marker content. Py-GC/MS results indicated that hydrolysis is an inevitable degradation process during the burial of succinite. Additionally, amber went slow oxidation in low-oxygen environments, leading to cyclization and the formation of polycyclic structures. This research highlights the ageing characteristics of amber artefacts and demonstrates that Py-GC/MS is an effective way in determining the provenance of significantly degraded samples, providing clues to ancient trade routes and cultural exchanges via the Silk Road.