title: Breath analysis with broadly tunable quantum cascade lasers.
abstract: With the availability of broadly tunable external cavity quantum cascade lasers (EC-QCLs), particularly bright mid-infrared (MIR; 3-20 μm) light sources are available offering high spectral brightness along with an analytically relevant spectral tuning range of >2 μm. Accurate isotope ratio determination of (12)CO2 and (13)CO2 in exhaled breath is of critical importance in the field of breath analysis, which may be addressed via measurements in the MIR spectral regime. Here, we combine for the first time an EC-QCL tunable across the (12)CO2/(13)CO2 spectral band with a miniaturized hollow waveguide gas cell for quantitatively determining the (12)CO2/(13)CO2 ratio within the exhaled breath of mice. Due to partially overlapping spectral features, these studies are augmented by appropriate multivariate data evaluation and calibration techniques based on partial least-squares regression along with optimized data preprocessing. Highly accurate determinations of the isotope ratio within breath samples collected from a mouse intensive care unit validated via hyphenated gas chromatography-mass spectrometry confirm the viability of IR-HWG-EC-QCL sensing techniques for isotope-selective exhaled breath analysis.
authors: Institute of Analytical and Bioanalytical Chemistry, University of Ulm, 89081 Ulm, Germany.
authors: Katharina
authors: K
authors: Wörle
authors: Felicia
authors: F
authors: Seichter
authors: Andreas
authors: A
authors: Wilk
authors: Chris
authors: C
authors: Armacost
authors: Tim
authors: T
authors: Day
authors: Matthias
authors: M
authors: Godejohann
authors: Ulrich
authors: U
authors: Wachter
authors: Josef
authors: J
authors: Vogt
authors: Peter
authors: P
authors: Radermacher
authors: Boris
authors: B
authors: Mizaikoff
mesh_terms: D001944:Breath Tests / Q000295:instrumentation*; D002245:Carbon Dioxide / Q000032:analysis; D006801:Humans; D007834:Lasers; D012666:Semiconductors
chemical_list: D002245:Carbon Dioxide