Discrete sample introduction module for quantitative and isotopic analysis of methane and other gases by cavity ring-down spectroscopy

Environmental Science & Technology
By: , and 

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Abstract

Carbon dioxide (CO2) and methane (CH4) are natural and anthropogenic products that play a central role in the global carbon cycle and regulating Earth’s climate. Applications utilizing laser absorption spectroscopy, which continuously measure concentrations and stable isotope ratios of these greenhouse gases, are routinely employed to measure the source and magnitude of atmospheric inputs. We developed a discrete sample introduction module (DSIM) to enable measurements of methane and CO2 concentrations and δ13C values from limited volume (5–100 mL) gas samples when interfaced with a commercially available cavity ring-down spectroscopy (CRDS) analyzer. The analysis has a dynamic range that spans six orders of magnitude from 100% analyte to the lower limit of instrument detection (2 ppm). We demonstrate system performance for methane by comparing concentrations and δ13C results from the DSIM-CRDS system and traditional methods for a variety of sample types, including low concentration (nanomolar CH4) seawater and high concentration (>90% CH4) natural gas. The expansive concentration range of the field-portable DSIM-CRDS system can measure enhances analytical performance for investigating methane and CO2 dynamics and, potentially, other gases measured by laser absorption spectroscopy.

Publication type Article
Publication Subtype Journal Article
Title Discrete sample introduction module for quantitative and isotopic analysis of methane and other gases by cavity ring-down spectroscopy
Series title Environmental Science & Technology
DOI 10.1021/acs.est.1c01386
Volume 55
Issue 17
Year Published 2021
Language English
Publisher American Chemical Society
Contributing office(s) Woods Hole Coastal and Marine Science Center
Description 9 p.
First page 12066
Last page 12074
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