UC Davis

Multi-component gas analysis under industrial process conditions (elevated pressure, near-saturation humidity, dynamic composition) challenges established analytical modalities: infrared absorption cannot detect homonuclear diatomics (N2, O2), gas chromatography is offline, and electrochemical sensors drift under sustained humidity. This paper presents a hollow-core anti-resonant fiber-enhanced Raman spectrometer for simultaneous, standard-free detection of five process gases (N2, O2, CO2, ethanol vapor, H2O) and quantification of the three that define the bulk gas balance (N2, O2, CO2). A threegas normalization framework anchored to atmospheric N2 as an internal standard yields quantitative molar fractions from peak-area ratios using relative Raman cross-sections, without external calibration, pressure sensing, or absolute intensity reference. The instrument was deployed for six days on a temperature-controlled wine fermentation, in a research winery environment and powered down between daily acquisitions. Over that period the instrument maintained wavenumber stability below 0.021 cm−1 (relative standard deviation ≤ 0.0013%), signal-to-noise ratios of 101:1 to 955:1 for the major gases, limits of detection of 0.33, 0.25 and 0.26 mol% for CO2, N2 and O2 respectively at 1000 s and 515 kPa absolute, well below the 9 to 62 mol% the three species actually occupied. The oxygen-to-nitrogen response factor governing the framework was determined experimentally from ambient air. Composition is reported on a three-gas basis; CO2 was quantified from its 1.10 mol% limit of quantification to a maximum of 52 mol%, a 47-fold range.