Adoption and evaluation of a sample pretreatment protocol for radiocarbon dating of cremated bones at HEKAL

A comparative study was undertaken to adopt and evaluate a radiocarbon ( ¹⁴ C) preparation procedure for accelerator mass spectrometry (AMS) measurements of cremated bones at our laboratory, including different types of archaeological samples (cremated bone, bone, charcoal, charred grain). All ¹⁴ C analyses were performed using the EnvironMICADAS AMS instrument at the Hertelendi Laboratory of Environmental Studies (HEKAL) and the ancillary analyses were also performed at the Institute for Nuclear Research (ATOMKI). After the physical and chemical cleaning of cremated bones, CO2 was extracted by acid hydrolysis followed by sealed-tube graphitization and ¹⁴ C measurement. The supplementary δ ¹³ C measurements were also performed on CO2 gas while FTIR was measured on the powder fraction. Based on the FTIR and ¹⁴ C analyses, our chemical pretreatment protocol was successful in removing contamination from the samples. Good reproducibility was obtained for the 0.2-0.3 mm fraction of blind-tested cremated samples and a maximum age difference of only 150 yr was found for the remaining case studies. This confirms the reliability of our procedure for ¹⁴ C dating of cremated bones. However, in one case study, the age difference of 300 yr between two cremated fragments originating from the same urn shows that other processes affecting the cremated samples in the post-burial environment can substantially influence the ¹⁴ C age, so caution must be exercised.