Universal Interface for Online Measurements of 13C and 14C Concentrations in CO2
Melina Wertnik1,2, Dr. Caroline Welte1,2, Dr Lukas Wacker2, Philip Gautschi2, Dr. Negar Haghipour1,2
1ETH Zurich Biogeoscience Group, Zurich, Switzerland, 2ETH Zurich Laboratory for Ion Beam Physics, Zurich, Switzerland
Combined δ¹³C and ¹⁴C/¹²C measurements are a staple ingredient for carbon cycle studies, biogeoscience and paleoclimatology because together they provide information not only about the source (e.g. marine or terrestrial) and sink but also about time (e.g. age mixtures). For organic samples ¹³C and ¹⁴C can be measured concurrently by using a commercially available Elemental Analyser – Isotope Ratio Mass Spectrometer (EA-IRMS) system coupled with the ETH Zurich Accelerator Mass Spectrometer (AMS). Here, the CO₂ from the EA is first introduced to the IRMS and then split for introduction into the AMS. However, the existing system is limited to sample materials that can be processed in an EA.
Here we present an update to our universal gas interface for ¹⁴C analysis which allows simultaneous δ¹³C measurements independent of the source material (e.g. carbonates, cracker samples, etc.). The samples are converted to CO₂ that is collected in a syringe and diluted with Helium to a concentration of 4%, ensuring reproducible conditions for subsequent measurements. The CO₂-helium gas mixture is then fed over two separate capillaries into the Gas Chromatography (GC)-inlet of the IRMS as well as the gas ion source of the AMS for simultaneous δ¹³C and ¹⁴C/¹²C analysis.
The performance of the proof of concept for simultaneous δ¹³C and ¹⁴C/¹²C analysis will be demonstrated on various representative standard materials.
 C. P. McIntyre et al., ‘Online 13C and 14C Gas Measurements by EA-IRMS-AMS at ETH Zürich’, Radiocarbon, vol. 59, no. 3, pp. 893–903, Oct. 2016, doi: 10.1017/rdc.2016.68.
 L. Wacker et al., ‘A versatile gas interface for routine radiocarbon analysis with a gas ion source’, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, vol. 294, pp. 315–319, Jan. 2013, doi: 10.1016/j.nimb.2012.02.009.
Melina Wertnik studied physics at ETH Zurich and now works there as a PhD candidate in the groups for biogeoscience and ion beam physics.