title: An automated system for stable isotope and concentration analyses of CO2 from small atmospheric samples.
abstract: We have developed an automated, continuous-flow isotope ratio mass spectrometry (CF-IRMS) system for the analysis of delta(13)C, delta(18)O, and CO(2) concentration (micromol mol(-1)) ([CO(2)]) from 2 mL of atmospheric air. Two replicate 1 mL aliquots of atmospheric air are sequentially sampled from fifteen 100 mL flasks. The atmospheric sample is inserted into a helium stream and sent through a gas chromatograph for separation of the gases and subsequent IRMS analysis. Two delta(13)C and delta(18)O standards and five [CO(2)] standards are run with each set of fifteen samples. We obtained a precision of 0.06 per thousand, 0.11 per thousand, and 0.48 micromol mol(-1) for delta(13)C, delta(18)O, and [CO(2)], respectively, by analyzing fifty 100 mL samples filled from five cylinders with a [CO(2)] range of 275 micromol mol(-1). Accuracy was determined by comparison with established methods (dual-inlet IRMS, and nondispersive infrared gas analysis) and found to have a mean offset of 0.00 per thousand, -0.09 per thousand, and -0.26 micromol mol(-1) for delta(13)C and delta(18)O, and [CO(2)], respectively.
authors.affiliation: Stable Isotope Ratio Facility for Environmental Research, Department of Biology, University of Utah, 257 S. 1400 E., Salt Lake City, UT 84112, USA. schauer@biology.utah.edu
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Schauer
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Lott
authors.forename: Craig S
authors.initials: CS
authors.lastname: Cook
authors.forename: James R
authors.initials: JR
authors.lastname: Ehleringer
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D001272:Atmosphere / Q000737:chemistry*; D002245:Carbon Dioxide / Q000032:analysis*; D002247:Carbon Isotopes; D008401:Gas Chromatography-Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D010103:Oxygen Isotopes; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods
chemical_list: D000393:Air Pollutants; D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D002245:Carbon Dioxide