An automated system for stable isotope and concentration analyses of CO2 from small atmospheric samples |
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Authors: | Schauer Andrew J Lott Michael J Cook Craig S Ehleringer James R |
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Institution: | 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 |
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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. |
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