12 research outputs found
Breath Analysis with Broadly Tunable Quantum Cascade Lasers
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 <sup>12</sup>CO<sub>2</sub> and <sup>13</sup>CO<sub>2</sub> 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 <sup>12</sup>CO<sub>2</sub>/<sup>13</sup>CO<sub>2</sub> spectral band with a miniaturized hollow waveguide
gas cell for quantitatively determining the <sup>12</sup>CO<sub>2</sub>/<sup>13</sup>CO<sub>2</sub> 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