Fiber-Enhanced Raman Multigas Spectroscopy: A Versatile Tool for Environmental Gas Sensing and Breath Analysis

Versatile multi-gas analysis bears high potential for environmental sensing of climate relevant gases and non-invasive early-stage diagnosis of disease states in human breath. In this contribution, a fiber enhanced Raman spectroscopic (FERS) analysis of a suite of climate relevant atmospheric gases is presented, which allowed for reliable quantification of CH4, CO2, and N2O alongside N2 and O2 with just one single measurement. A highly improved analytical sensitivity was achieved, down to a limit of detection of 4 ppm CH4 (only 4 fmol) within 1 second measurement time. The high potential of FERS for the detection of disease markers was demonstrated with the analysis of 27 nL exhaled human breath. The natural isotopes 13CO2 and 14N15N were quantified at low levels, simultaneously with the major breath components N2, O2, and 12CO2 in a high dynamic range of six orders of magnitude. The natural abundances of 13CO2 and 14N15N were experimentally quantified in very good agreement to theoretical values. A fiber adapter assembly and gas filling setup was designed for rapid and automated analysis of multi-gas compositions and their fluctuations within seconds and without the need for optical readjustment of the sensor arrangement. Based on the abilities of such miniaturized FERS system, we expect high potential for the diagnosis of clinically administered 13C-labeled CO2 in human breath and also foresee high impact for disease detection via biologically vital nitrogen compounds.