Real-time analysis of carbon monoxide isotopologues in biogenic gas samples via infrared laser spectroscopy

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We propose to explore a laser spectroscopic approach for quantitative real-time detection of biogenic carbon monoxide (CO). CO is generated and released in low concentrations during the metabolism of many biological systems; for example, it is a constituent of exhaled human breath. Next to the main abundant isotopic species 12C16O, we plan to extend the analysis to rare CO isotopologues, like 13C16O. For this purpose, cavity leak-out spectroscopy (CALOS) - a variant of ring-down spectroscopy with continuous-wave lasers - appears very promising; CALOS is one of the most sensitive high-resolution infrared spectroscopy techniques. The minimum detectable absorption is currently down to 10-10/cm. The CALOS approach is very attractive for all analytical tasks which require highest sensitivity, specificity, and fast response time. The proposed work shall set the stage for making this methodology applicable for the isotope-selective online analysis of CO gas fractions in complex biogenic gas samples. The results are of relevance for biomedical and pharmacological studies, where the use of stable isotopes, like 13C, as labels for "tracer" experiments is a key issue.