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-vol ume metal bellows. Compressed air from the bellows is then routed to a non- dispersive infrared gas analyzer (1RGA). Tests indicate that this configura tion has an overall accuracy of +/-0.3 and a precision of +/-0.2 mu mol mol (-1) and will work with flask volumes as low as 64 ml air (STP). When combi ned with continuous-flow mass spectrometry approaches, both atmospheric CO2 mixing ratios and isotope ratio analyses can now be, routinely analyzed wi th small flasks, enabling more extensive sampling Of CO2 exchange processes between the biosphere and the atmosphere. (C) 2001 Elsevier Science B.V. A ll rights reserved.