Co-Localized Infrared-Raman Spectroscopy: An Innovative Approach for the Quantitative In Situ Analysis of Gas Mixtures at High Pressures.

This article spotlights the interest in using co-localized infrared (IR)-Raman spectroscopy as an innovative approach for the in situ monitoring of complex gas mixtures, e.g., hydrogen (H₂), nitrogen (N₂), carbon monoxide (CO), carbon dioxide (CO₂), and methane (CH₄), at elevated pressures. Thus, by combining the IR and Raman spectra of CH₄, we proposed a new methodology for the calibration of the Raman spectra to circumvent the fact that Raman intensities are arbitrary (laser power, instrument response, integration time, and fluorescence). Applying our methodology to scale several consecutive experiments, the concentrations of all gases were determined with a relative uncertainty lower than 10%. These original results highlight the interest in co-localized IR-Raman spectroscopy analysis in a single cell for the quantitative analysis of solutes by Raman spectroscopy without the use of an internal standard.