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- Title
Diode laser absorption spectrometry for <sup>13</sup>CO<sub>2</sub>/<sup>12</sup>CO<sub>2</sub> isotope ratio analysis: Investigation on precision and accuracy levels.
- Authors
Castrillo, A.; Casa, G.; Kerstel, E.; Gianfrani, L.
- Abstract
Near-infrared laser spectroscopy is used to measure the 13C/12C isotope abundance ratio in gas phase carbon dioxide. The spectrometer, developed expressly for field applications, is based on a 2 μm distributed feedback diode laser in combination with sensitive wavelength modulation detection. It is characterized by a simplified optical layout, in which a single detector and associated electronics are used to probe absorptions of a pair of 13CO2 and 12CO2 lines, simultaneously in a sample, as well as a reference gas. For a careful investigation of the achievable precision and accuracy levels, we carried out a variety of laboratory tests on CO2 samples with different isotopic compositions, calibrated with respect to the international standard material by means of isotope ratio mass spectrometry. The 1-σ accuracy of the 13CO2/12CO2 determinations, reported in the so-called δ notation, is about 0.5‰ (including both statistical and systematic errors), for δ-values in the range from -30‰ to +20‰. We show that the major source of systematic errors is a consequence of the non-linearity of the Lambert–Beer absorption law, and can be corrected for to a very high degree of accuracy.
- Subjects
DIODES; LASERS in physics; ABSORPTION spectra; MEASUREMENT errors; CARBON dioxide; ISOTOPES; PHYSICS
- Publication
Applied Physics B: Lasers & Optics, 2005, Vol 81, Issue 6, p863
- ISSN
0946-2171
- Publication type
Article
- DOI
10.1007/s00340-005-1949-4