Precision trace gas analysis by FT-IR spectroscopy. 2. The 13C/12C isotope ratio of CO2.
We report the development of a method of carbon stable isotope ratio analysis based on 1-cm-1 resolution Fourier transform infrared (FT-IR) spectroscopy, deployable in both laboratory and field applications. We demonstrate the determination of the 13C/12C ratio of CO2 (i.e., delta 13CO2) in air with an analytical precision of the order of +/- 0.1/1000 (i.e., +/- 0.01%). The FT-IR method relies on calibration using synthetically calculated absorbance spectra and a multivariate calibration algorithm. The method requires no sample preparation other than optional drying of the sample and may be applied directly to ambient air samples containing approximately 350 mumol mol-1 CO2 (molar mixing ratio). It may also be applied to samples more concentrated in CO2, such as human breath, approximately 5% CO2. We demonstrate the utility of the technique to the analysis of delta 13CO2 in air during an experimental field campaign and to the laboratory-based analysis of human breath. A similar method could also be used to determine the H/D ratio in atmospheric water vapor.
Esler
M B
MB
Department of Chemistry, University of Wollongong, Australia. mesler@uow.edu.au
Griffith
D W
DW
Wilson
S R
SR
Steele
L P
LP
D000388:Air / Q000032:analysis; D002244:Carbon / Q000032:analysis*; D002245:Carbon Dioxide / Q000032:analysis*; D002247:Carbon Isotopes; D016481:Helicobacter Infections / Q000175:diagnosis; D006801:Humans; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
D002247:Carbon Isotopes; D002245:Carbon Dioxide; D002244:Carbon