High-precision determination of the 13CO2/12CO2 isotope ratio using a portable 2.008-μm diode-laser spectrometer

Abstract

High-precision determination of the (CO2)-C-13/(CO2)-C-12 isotope ratio using a portable 2.008-mu m diode

Method allows for continuous monitoring of volcanic gases

“…This indicates that a mixing between magmatic and sedimentary fluids is occurring probably at mantle level [Tedesco, 1994]. The near-infrared DLS is a simplified and more compact version of that reported else where [Gagliardi et al, 2003]. Designed to work in a volcanic environment, it is housed in a 60 by 60 centimeter square breadboard, thermally-insulated, and is fully-controlled by a laptop computer (Figure l).C0 2 is con veyed to the DLS after the fluid is cooled in a Pyrex trap and the H 2 0 is separated from the whole gas phase.…”

Diode laser absorption spectrometry for 13CO2/12CO2 isotope ratio analysis: Investigation on precision and accuracy levels

“…The experimental work described in the present paper is the continuation of our previously published work [16]. We have developed a simplified version of the earlier spectrometer, implementing a compact design suitable for field applications and, particularly, for in-situ isotope ratio determinations in volcanic CO 2 .…”

“…Moreover, high quality, distributed feed-back (DFB) diode lasers are commercially available in this region. Implementing wavelength modulation spectroscopy to sensitively monitor the laser absorption in a multiple reflection cell, we have demonstrated the feasibility of high precision δ 13 C determinations in mixtures of CO 2 and N 2 , and provided a clear indication of the most promising way to satisfy the new demand for portable isotopic analysers [16]. A radically different approach to build a compact instrument would involve the use of a room-temperature or thermo-electrically cooled quantum cascade (QC) spectrometer at 4.3 µm, as recently discussed by Weidmann et al [17].…”

Mid-infrared laser spectroscopic determination of isotope ratios of N2O at trace levels using wavelength modulation and balanced path length detection

“…At low concentrations the detector signal measured with wavelength modulation is proportional to the concentration of the gas [28]. Therefore, the δ-value (1) can be obtained by taking the ratio of the measured signals of the sample and the reference gas for both isotopomers and by comparing these ratios for the absorption lines of the main and the less abundant isotopomers.…”

“…By repeating this procedure for each isotopomer I and comparing the slopes I a of these curves of the main and the less abundant isotopomers, the difference of the isotopic composition between the sample gas and the reference gas can be calculated [28]: Figure 3 shows the result for wavelength modulation with single long path detection.…”