2:35 PM - 2:50 PM
[U05-04] Bile acids as tracers of human and animal activity: a method proposal
Keywords:organic geochemistry, methods, biomarker
Due to taxa-specificity and relatively high resistance to degradation, the bile acids (BAs), metabolites of cholesterol, may work as biomarkers - palaeoenvironmental and geoarchaeological tools indicating the past activity of vertebrates. It is a prominent instrument for Anthropocene study in aspects of land-use, animal husbandry, and human population changes.
The common method for BAs, gas chromatography-mass spectrometry (GC-MS), requires complex pre-treatment. Liquid chromatography-mass spectrometry (LC-MS) can identify BAs without derivatization, and the purpose of this study was to establish an advanced LC-MS method that could be applied to soils and sediments routinely. The limit of detection of the proposed LC-MS method is 0.01 ng/μl, which is theoretically equivalent to 0.1 ng/g dry soil (if following the full protocol).
A comparison of different extraction methods was performed. For soil contaminated with faeces, the sonication and accelerated solvent extraction (ASE) showed similar results with the negligible advantage of sonication. Notably, the recovery of added standards differed from one of the natural bile acids in faeces. Thus, the quantification using the internal standard method has to be done with precautions.
The method was tested on faeces of different species and archaeological soils. The faecal BA profile of Ezo sika deer is newly reported. Deoxycholic and lithocholic acids in a ratio that is typical for humans were found in the soil layer from the Kashiwagigawa 9 archaeological site (Hokkaido, Japan) containing most artifacts preliminarily attributed to the Jomon period.
The common method for BAs, gas chromatography-mass spectrometry (GC-MS), requires complex pre-treatment. Liquid chromatography-mass spectrometry (LC-MS) can identify BAs without derivatization, and the purpose of this study was to establish an advanced LC-MS method that could be applied to soils and sediments routinely. The limit of detection of the proposed LC-MS method is 0.01 ng/μl, which is theoretically equivalent to 0.1 ng/g dry soil (if following the full protocol).
A comparison of different extraction methods was performed. For soil contaminated with faeces, the sonication and accelerated solvent extraction (ASE) showed similar results with the negligible advantage of sonication. Notably, the recovery of added standards differed from one of the natural bile acids in faeces. Thus, the quantification using the internal standard method has to be done with precautions.
The method was tested on faeces of different species and archaeological soils. The faecal BA profile of Ezo sika deer is newly reported. Deoxycholic and lithocholic acids in a ratio that is typical for humans were found in the soil layer from the Kashiwagigawa 9 archaeological site (Hokkaido, Japan) containing most artifacts preliminarily attributed to the Jomon period.