(The Agony and the Ecstasy of) CO2 Dual Inlet Measurements - Michelle Chartrand
Michelle Chartrand, Juris Meija and Zoltan Mester
Metrology, National Research Council Canada
Dual inlet measurements of CO2 are considered the holy grail of isotopic measurements, with uncertainties usually a magnitude lower than those obtained from EA-IRMS. However, these measurements require numerous tedious steps such as converting carbonates to CO2 gas, sample introduction techniques, and low-throughput sampling regimes. A project was undertaken at NRC to characterize the carbon and oxygen isotope delta values of 13 CO2 gas cylinders with nominal δVPDB(13C) values ranging from +10 to -40 ‰. Strategies for cross-contamination evaluation, and carbon and oxygen isotope delta value assignment via three different calibration techniques: direct measurement, calibration curve and global least squares adjustment involving 1000+ measurements, will be presented. The results will demonstrate that NRC can measure carbon and oxygen isotope delta measurements of CO2 gas with standard precisions of 0.01 ‰ and 0.04 ‰, respectively.