UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2009 Meeting


Section: Optics, Spectroscopy, Plasma and Lasers


Title:
Photoacoustic Spectroscopy Devices for Measurements of Ammonia Absorption Coefficients with Applications in Clinical Diagnosis by Breath Analysis


Authors:
C. Achim, D. C. Dumitras, C. Matei, R. Cernat


Affiliation:
Department of Lasers, National Institute for Laser, Plasma and Radiation Physics,

P. O. Box MG-36, Bucharest, Magurele, Romania


E-mail
E-mail: cristina.achim@inflpr.ro


Keywords:
Laser photoacoustic spectroscopy, absorption coefficients of ammonia, breath analysis


Abstract:
Breath analysis provides a unique window to the blood compositions. Human alveolar breath typically contains many biomarkers. Breath analysis might offer a new approach to the diagnosis of diseases and assessment of volatile organic compounds content [1]. Laser photoacoustic spectroscopy in the mid-infrared region offers a promising new effective technique for the quantitative analysis of trace ammonia in human breath [1, 2]. This technique uses a continuous wave CO2 laser, tunable between 9.2 and 10.8 m with a high power (50 W) allowing the detection of very small gas traces. We report precise values of ammonia absorption coefficients at the CO2 laser wavelengths measured on our photoacoustic (PA) cell in extracavity configuration. Also, we propose a general scheme for detection of ammonia levels in expired human breath. One can use a more particular scheme to determine the duration of a single session for an optimal degree of dialysis at patients with end-stage renal disease. In the present work, ammonia absorption was measured at both branches of the CO2 laser lines by using a calibrated mixture of 10 ppm NH3 in N2. The PA method offers a high sensitivity at the sub-ppb level with a minimal detectable absorption of 10-8 cm-1, a cell responsivity independent of radiation wavelength and the capability to detect a large number of chemical compounds [1, 3]. References 1. Wenqing Cao and Yixiang Duan, Breath analysis: potential for clinical diagnosis and exposure assessment, Clinical Chemistry, 52, 800-811 (2006). 2. S. Cristescu, D. C. Dumitras, D. C. Dutu, Ammonia and ethane absorption measurements with a tunable CO2 laser-based photoacoustic trace gas detector, Proc. SPIE 4070, pp. 457-464 (2000) 3. D. C. Dumitras, D. C. Dutu, C. Matei, A. M. Magureanu, M. Petrus, C. Popa, Laser photoacoustic spectroscopy: principles, instrumentation, and characterization, Journal of Optoelectronics and Advanced Materials, 9, 3655-3701 (2007)