Berlin 2001 – scientific programme
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MO: Molekülphysik
MO 12: Posters Friday: Spectroscopy
MO 12.3: Poster
Friday, April 6, 2001, 12:30–15:00, AT3
Real-Time Monitoring of Ethane in Human Breath using Mid-Infrared Cavity Leak-Out Spectroscopy — •H. Dahnke, D. Kleine, G. von Basum, P. Hering, and M. Mürtz — Institut für Lasermedizin, Universität Düsseldorf
Cavity ring-down spectroscopy (CRDS) is a very sensitive method to obtain absorption spectra of diluted gas samples. In this work we investigate the performance of a mid-infrared cw CRDS setup for the analysis of human breath samples. A tunable CO overtone sideband laser (λ = 3 µm) is utilized to excite a high-finesse cavity (length = 50 cm) which provides an effective optical absorption pathlength of 3.6 km. After excitation, the laser power is turned off and the subsequent decay of the radiation is observed. Using the advantages of the cw excitation we achieved a minimum detectable absorption coefficient in the order of 1.7 × 10−9/cm with a typical averaging time of 10 s [1]. We applied the spectrometer for the detection of ethane in human breath. Ethane is a selective indicator for lipid peroxidation, which allows to monitor the oxidative stress status of the human body. The natural human breath ethane fraction is in the low ppb region. Our presentation shows the way to meet the requirements of a sensitive real-time detection without cross interferences to other gases present in the human breath. In a first application we examined the exhalation of ethane after cigarette smoking. We monitored the decay of the ethane fraction over 3 hours after smoking. This demonstrates the capability of the spectrometer for medical breath test applications.
[1] H. Dahnke, D. Kleine, W. Urban, P. Hering, M. Mürtz, Appl. Phys. B 72, 121-125 (2001)