Technique to measure CO2 mixing ratio in small flasks with a bellows/IRGA system

We developed a laboratory method to obtain high precision CO2 mixing ratios in air samples contained in 100 ml glass flasks, which involves extracting air from the flask into a pre-evacuated manifold containing a variable-volume metal bellows. Compressed air from the bellows is then routed to a non-dispersive infrared gas analyzer (IRGA). Tests indicate that this configuration has an overall accuracy of ±0.3 and a precision of ±0.2 μmol mol−1 and will work with flask volumes as low as 64 ml air (STP). When combined with continuous-flow mass spectrometry approaches, both atmospheric CO2 mixing ratios and isotope ratio analyses can now be routinely analyzed with small flasks, enabling more extensive sampling of CO2 exchange processes between the biosphere and the atmosphere.