title: Terahertz gas-phase spectroscopy: chemometrics for security and medical applications.
abstract: We describe a spectrometer consisting of a vector network analyzer, a gas absorption cell, and a quasi-optical bench that acquires terahertz spectra of gaseous substances and mixtures. We tested volatile organic compounds that are medical biomarkers or chemicals which can be found on the US Environment Protection Agency list of harmful substances. Absorption spectra at gas pressures between 10 Pa and 5000 Pa were recorded. A subsequent multivariate data analysis demonstrated excellent qualitative and quantitative identification of pure substances and complex mixtures. The applied multivariate algorithms are principal components analysis, partial least square regression and soft independent modelling of class analogy.
authors.affiliation: German Aerospace Center, Institute of Optical Sensor Systems, Rutherfordstr. 2, 12489 Berlin, Germany. Philipp.Neumaier@dlr.de Heinz-Wilhelm.Huebers@dlr.de.
authors.forename: P F-X
authors.initials: PF
authors.lastname: Neumaier
authors.forename: K
authors.initials: K
authors.lastname: Schmalz
authors.forename: J
authors.initials: J
authors.lastname: Borngräber
authors.forename: R
authors.initials: R
authors.lastname: Wylde
authors.forename: H-W
authors.initials: HW
authors.lastname: Hübers
mesh_terms: D000465:Algorithms; D015415:Biomarkers / Q000032:analysis; D005740:Gases / Q000737:chemistry; D016018:Least-Squares Analysis; D009930:Organic Chemicals / Q000032:analysis*; D025341:Principal Component Analysis; D055068:Terahertz Spectroscopy
chemical_list: D015415:Biomarkers; D005740:Gases; D009930:Organic Chemicals