Enhancing AMS measurement precision with the incorporation of 𝛿13C data measured with IRMS

Within the CRC1211 project-Evolution at the Dry Limit, there is a need for precise dating analysis on soil samples extracted from the Atacama Desert. These samples have a characteristically low carbon content. Consequently, ultra-small samples containing approximately 2-20 𝜇g of carbon, need to be measured reliably. For this reason an elemental analyser (EA) and an isotope ratio mass spectrometer (IRMS) have been coupled to the 6 MV AMS system of CologneAMS as well as an existing gas interface (GIS). This provides a fully automated, online-analysis of ¹⁴C/¹²C, and it delivers precise values for 𝛿¹³C. We investigated whether this set-up improves the fractionation correction which is used in the ¹⁴C data evaluation. 𝛿¹³C values from multiple standard materials are measured quasi-simultaneously at the AMS and at the IRMS. Within these measurements we determined that the 𝛿¹³C values form both AMS and IRMS agree with each other within their respective errors. While the 𝛿¹³C AMS values scatter multiple orders higher than the IRMS values we concluded that the 𝛿¹³C IRMS values can be used for a reliable and more precise AMS measurements.