Characterization of absorption spectra of molecular constituents in the mid-infrared region and their role as potential markers for breath analysis

Abstract: The use of exhaled breath analysis in assessing the health status of human individuals is an intriguing concept that has attracted more and more attention during recent years. Although detection of species in breath can, to a certain extent, be made by both electrochemical and mass spectrometric techniques, these do not always provide sufficient sensitivity, selectivity and speed. Due to the development of new laser sources in the (MIR) wavelength region, absorption spectrometry (AS) has shown such good performance that MIR-AS techniques start to become more viable alternatives to breath analysis. Of the large number of species exhaled  (major species, which are in %-concentrations, e.g. H2O and CO2, minor species, which exist in ppm concentrations, e.g. CO and CH4, and trace species, which exist in low or sup-ppb concentrations), some are more important than others, such as Carbonyl Sulfide, Ethane, Ethylene and Formaldehyde, since they are important biomarkers for various diseases e.g. chronic respiratory diseases, acute lung transplant rejection, UV-radiation damage of the skin and gastro-esophageal/breast cancer. The present thesis consists of a compilation and analysis of possible transitions primarily in the 3-4 µm region that can be used for detecting such species by MIR-AS techniques.