Isotope selective analysis of CO(2) with tunable diode laser (TDL) spectroscopy in the NIR.
The performance of a home-built tunable diode laser (TDL) spectrometer, aimed at multi-line detection of carbon dioxide, has been evaluated and optimized. In the regime of the (30(0)1)(III) <-- (000) band of (12)CO(2) around 1.6 microm, the dominating isotope species (12)CO(2), (13)CO(2), and (12)C(18)O(16)O were detected simultaneously without interference by water vapor. Detection limits in the range of few ppmv were obtained for each species utilizing wavelength modulation (WM) spectroscopy with balanced detection in a long-path absorption cell set-up. High sensitivity in conjunction with high precision -- typically +/-1 (per thousand) and +/-6 (per thousand) for 3% and 0.7% of CO(2), respectively -- renders this experimental approach a promising analytical concept for isotope-ratio determination of carbon dioxide in soil and breath gas. For a moderate (12)CO(2) line, the pressure dependence of the line profile was characterized in detail, to account for pressure effects on sensitive measurements.
Horner
Gerald
G
Institute of Chemistry, Physical Chemistry, Potsdam University, Karl-Liebknecht Str. 24-25, D-14476 Potsdam-Golm, Germany.
Lau
Steffen
S
Kantor
Zoltan
Z
Lohmannsroben
Hans-Gerd
HG