Microdestructive analysis with Py-GC/MS for the identification of birch tar: a case study from the Huayang site in late Neolithic China

The use of birch tar has a long history, and its remains are found worldwide, especially in Europe, but few remains are found in Asia. Common characterization methods include gas chromatography/mass spectrometry (GC/MS), direct exposure electron ionization mass spectrometry (DE-MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Py-GC/MS requires no solvent extraction, less sample than GC/MS, and no statistical analysis compared to DE-MS. However, Py-GC/MS has been rarely applied to identify birch tar because some critical characteristic molecules of birch tar were not identified. In this study, we first reported some biomarkers of birch tar that could be identified by Py-GC/MS in terms of analyzing modern birch tar. Then, the analysis criteria were used to analyze archaeological samples adhered to stone artifacts from a late Neolithic site (about 4000 BP) in northeast China. The results provide the earliest evidence of the exploitation of birch tar in northeast Asia up to date.