T02_P07

Samples screening and treatment for accurate radiocarbon dating

Hajdas I¹,  Guidobaldi G¹, Haghipour N^1,2, Wyss K¹

¹Laboratory of Ion Beam Physics, ETH Zurich, Zurich, Switzerland, ²Earth Sciences Department, ETH Zurich, Zurich, Switzerland

Only carbon inherent to the material in quest of dating contains the original ¹⁴C signal from the time of formation or deposition. Apart from reservoir effects and calibration issues that must be considered, the major challenge in radiocarbon dating is the extraction of autogenic carbon. Various prescreening and purity checkups of sample material are vital to the choice of sample treatment. At the ¹⁴C prep laboratory ETH Zurich, the FTIR analysis supports the binocular investigations, which provides information on the sample's composition. Significantly, any anthropogenic conservation substances can be detected and identified, allowing for proper choice of treatment steps. Bulk sediments are cross-checked for carbonates or dolomite. Also, the treated samples are checked for purity before the final combustion. Occasionally, contaminated fractions are analyzed using a gas ion source to support evaluation.

Preservation of sample material is a crucial factor and assessing it helps choose an appropriate laboratory procedure. Currently, we estimate the N% and C/N ratio of the original bone sample to predict the success of collagen separation, although the use of FTIR analysis would simplify this step as the sample does not require weighing. On the other hand, the N% and C% of the original samples can be directly stored in the database after combustion in the elemental analyzer. Evaluation of procedures and their modifications is vital for an efficiently working laboratory. This paper will present an overview of methods applied to evaluate and treat various materials and samples.