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International Journal of Spectroscopy
Volume 2012 (2012), Article ID 894841, 10 pages
http://dx.doi.org/10.1155/2012/894841
Research Article

QCLAS and CRDS-Based CO Quantification as Aimed at in Breath Measurements

1Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
2VSL, Thijsseweg 11, 2629 JA Delft, The Netherlands
3Institut für Lasermedizin (ILM), Heinrich-Heine-Universität, Universitätsstraße 1, 40225 Düsseldorf, Germany

Received 7 September 2011; Revised 7 October 2011; Accepted 7 October 2011

Academic Editor: Veronica Vaida

Copyright © 2012 Javis Anyangwe Nwaboh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Laser-spectrometric methods to derive absolute and traceable carbon monoxide (CO) amount fractions in exhaled human breath could be of advantage for early disease detection as well as for treatment monitoring. As proof-of-principle laboratory experiment, we employed intra-pulse and continuous wave (cw) quantum cascade laser spectroscopy (QCLAS), both at 4.6 μm. Additional experiments were carried out applying cw cavity ring-down spectroscopy (CRDS) with a CO sideband laser and a QCL. We emphasize metrological data quality objectives, thatis, traceability and uncertainty, which could serve as essential benefits to exhaled breath measurements. The results were evaluated and compared on a 100 μmol/mol CO level using the two QCLAS spectrometers, and the cw CO sideband laser CRDS setup. The relative standard uncertainties of the pulsed and the cw QCLAS CO amount fraction results were ±4.8 and ±2.8%, respectively, that from the CO sideband laser CRDS was ±2.7%. Sensitivities down to a 3 nmol/mol CO level were finally demonstrated and quantified by means of cw CRDS equipped with a QCL yielding standard uncertainties of about ±2.5 that are exclusively limited by the available line strength figure quality. With this study we demonstrate the achieved comparability of CO quantifications, adhering metrological principles.