T01_04

Testing the measurement of small (<50 ug C) graphite samples on the ORAU MICADAS

Becerra-Valdivia L¹,  Cameron J¹, Spindler L¹, Gianni M¹, Chivall D¹, Bronk Ramsey C¹, Wood R¹

¹Oxford Radiocarbon Acceleration Unit, Oxford, United Kingdom

The Oxford Radiocarbon Accelerator Unit (ORAU) has processed about 5,000 samples for research and commercial purposes since the installation of a Mini Carbon Dating System AMS (MICADAS; Ionplus AG, CH) in 2019. Very few of the measurements produced, however, have been on graphite samples of less than 100 ug C. Given the need to reduce sample size in order to adequately address research questions across disciplines, a study was aimed at testing our ability to reliably measure very small graphite samples (<50 ug C) as an alternative to gas measurement by reassessing our current graphitisation (iron-catalysed hydrogen reduction), combustion and cleaning procedures. This included decreasing reaction vessel volume, increasing the mass of iron powder used, and decreasing graphitisation temperature to assess isotopic fractionation and AMS current behaviour. Throughout these experiments, efforts were made to efficiently and minimally adjust our current equipment set-up for simplicity. Here we present the preliminary results of this study and discuss archaeological and paleoecological applications.