We use over thirty different pre-treatment methods for samples of different kinds and in different states of preservation. These methods have been developed as part of the laboratory's research programs.
The Oxford Radiocarbon Accelerator Unit has radiocarbon dated over 40,000 samples using accelerator mass spectrometry (AMS) since its inception in the early 1980s, and is currently dating about 2000, mainly archaeological, samples per year. These samples fit into 5 general groups according to their chemical components, namely:
• Collagen-containing materials, i.e. bone, tooth, antler, ivory
• Charcoal and charred material, e.g. wood and seeds
• Cellulose-containing materials,e.g. wood, seeds, plant remains, textiles, and paper
• Shells, other carbonates, and cremated bones
• Other materials, e.g. hair, sediments, carbonized pottery residues
The pretreatment methods applied range from simple acid/base/acid treatments to separation of amino acids from proteins using HPLC.
Our pretreatment and extraction methods have previously been outlined in several publications, including our regular Archaeometry Datelists, and in refereed journal articles, that most recent of which is Brock et al. (2010a). Our approach to pretreatment is based on our experience of dating over 40,000 samples. The quality of sample is also vital, and demands a sensitive response on the part of the laboratory and a seamless line of communication between submitter and laboratory.
In accordance with our ISO 9001:2015 accreditation, we have over 25 pre-treatment methods that provide standardised procedures for preparing samples for AMS dating at the ORAU. The general approach of sample pre-treatment chemistry is to attempt to date materials that can be chemically characterised rather than dating bulk samples which may be inhomogeneous. Our approach is to select identifiable material that is representative of the bulk as a whole, for example, taking macrofossils from peat or sampling charcoal fragments from sediment. Further problems arise when considering samples which may be homogeneous but which acquire carbon from other sources during post-depositional diagenesis. Our pre-treatment protocols are designed to reduce the likelihood of contamination to a level where it contributes an insignificant amount of error to the final radiocarbon measurement.
Compound-Specific Radiocarbon Analysis
For radiocarbon results to be accurate, samples must be free of contaminating carbon. Sample pre‐treatment using a high‐performance liquid chromatography (HPLC) approach has been developed at the Oxford Radiocarbon Accelerator Unit (ORAU) as an alternative to conventional methods for dating heavily contaminated bones. This approach isolates hydroxyproline from bone collagen, enabling a purified bone‐specific fraction to then be radiocarbon dated by accelerator mass spectrometry (AMS).
Please get in touch if you would like to discuss submitting your samples for compound-specific dating. See our Charges and Turnaround Times page for details on pricing.
