Improved method for simultaneous determination of the carbon isotopic composition and concentration of atmospheric CO2 using CF-IRMS

Abstract

Determination of the concentration and isotopic composition of atmospheric CO2 is essential for the identification of sources and sinks of anthropogenic CO2 and the monitoring of various emission reduction techniques, such as geological CO2 storage. A customized and convenient method was proposed to determine the carbon isotopic composition and concentration of CO2 of air samples simultaneously using a continuous flow-isotope ratio mass spectrometer (CF-IRMS) interfaced with a GasBench II (Thermo Fisher Scientific, Bremen, Germany). Convenient sampling and isotopic analysis were achieved using 12-mL Exetainer vials with open tops, screw caps, and rubber septa for both air sampling and isotopic analysis. The proposed method differs from previously reported methods in several aspects, including the convenience of sampling and analysis, and high accuracy and precision despite small sample consumption. Combined with the Keeling plot technique, this method allows accurate determination of the isotope composition of atmospheric CO2. The proposed technique can be applied in various studies involving the isotopic composition and concentration of CO2, such as diagnosing cancer, tracing of anthropogenic CO2 and monitoring of leakage from subsurface CO2 storage.