BioArCh has a well-established profile for excellence in stable isotope research investigating diet and subsistence strategies in past societies across the globe, ranging from the Mesolithic to Post Medieval periods.
BioArCh itself is home to laboratory facilities for both research and teaching dedicated to the preparation of organic remains for isotopic analysis, particularly protein extraction from bone (collagen), tooth (dentine) and hair (keratin) and also deposits such as charred food crusts from ceramic vessels and archaeological plant remains. We have various specialist equipment for these procedures including a freeze drier and a microbalance, listed below.
We have two isotope ratio mass spectrometers housed with the Envrionment building.
A Sercon continuous flow 20-22 Isotope Ratio Mass Spectrometer interfaced with a Universal Sercon GSL preparation unit which is configured for high-quality isotope ratio measurements for a range of light isotopes:
Carbon (13C), Nitrogen (15N) in solid samples, such as lyophilized collagen, plant materials, soils and dried extracts (combustion)
Hydrogen (HD) and Oxygen (18O) in solid organic samples (pyrolysis)
A Thermo Delta V advantage coupled to a Trace GC and Flash 2000 Elemental analyser. This is a versitile instrumnet capable of determining 15N in amino acids for example in hydrolysed collagen samples or carbon (13C) and Nitrogen (15N) in solid samples.
During Elemental Analysis-Isotope Ratio Mass Spectrometry (EA-IRMS), samples are aliquoted into tin capsules and loaded into an autosampler on the Sercon GSL preparation module. The samples are dropped individually into a 1000ºC furnace and combusted in the presence of oxygen, chromium oxide and silvered copper oxide. The resultant gases are swept through a helium stream and passed through a reduction unit (copper oxide) to remove oxides. N2 and CO2 are separated on a GC column before entering the IRMS where the gas species are separated by their different masses in a magnetic field and are collected in Faraday cups. The dual inlet allows us to analyze both 13C and 15N in the same sample, or we have the option of using a CO2 trap to measure 15N only in the case of materials that contain very low levels of nitrogen, such as plant remains.
Analysis of Oxygen and Hydrogen takes place in the high temperature furnace, during which samples aliquoted into silver capsules are dropped into the furnace held at 1300°C. As before, the resultant gases are swept through on a stream of helium to the mass spectrometer for analysis.
Our BSc and MSc students have the option of conducting stable isotope projects involving the skeletal collections (human and animal) housed at York and will gain hands on experience of the extraction techniques and using the IRMS.
We also have an interest in participating in outside collaborative projects. For further information contact our administrator, Josie Thomas.