Improved Precision of 14C Measurements for CH4 and CO2 Using GC and Continuous-Flow AMS Achieved by Summation of Repeated Injections

Cameron McIntyre
2013 Radiocarbon: An International Journal of Cosmogenic Isotope Research  
Compound specific radiocarbon measurements can be made instantaneously using a gas chromatograph (GC) combustion system coupled to a 14 C AMS system fitted with a gas ion source. Samples below 10 µg C can be analyzed but the precision is reduced to 5-10% because of lower source efficiency. We modified our GC for CH 4 and CO 2 analysis and injected samples multiple times to sum data and increase precision. We attained a maximum precision of 0.6% for modern CO 2 from 25 injections of 27 µg C and
more » ... background of ~0.5% (40 kyr) for ancient methane. The 14 C content of dissolved CO 2 and CH 4 in water samples collected at a deep-sea hydrothermal vent and a serpentine mud volcano was measured and the results for the vent sample are consistent with previously published data. Further experiments are required to determine a calibration and correction procedure to maximize accuracy.
doi:10.2458/azu_js_rc.55.16348 fatcat:gajru2kg7veltjyarwqf5ecqje