Fast and Highly Sensitive Fiber-Enhanced Raman Spectroscopic Monitoring of Molecular H2 and CH4 for Point-of-Care Diagnosis of Malabsorption Disorders in Exhaled XXXX Breath.

@entity1 @entity28 @entity1353 @entity14782 @entity3627 @entity209 @entity694 @entity8032
UNASSIGNED: Breath gas analysis is a novel powerful technique for noninvasive, early-stage diagnosis of @entity209 . Molecular hydrogen and methane are biomarkers for @entity694 , because of malabsorption of oligosaccharides (e.g., lactose or fructose) and for small intestinal bacterial @entity8032 . Recently, the presence of these gases in exhaled breath was also correlated with @entity28 . Here, we report on the highly selective and sensitive detection of molecular hydrogen and methane within a complex gas mixture (consisting of H2, CH4, N2, O2, and @entity3627 ) by means of @entity14782 ( @entity14782 ). An elaborate @entity14782 setup with a microstructured hollow core photonic crystal fiber (HCPCF) provided a highly improved analytical sensitivity. The simultaneous monitoring of H2 with all other gases was achieved by a combination of rotational (H2) and vibrational (other gases) Raman spectroscopy within the limited spectral transmission range of the HCPCF. The HCPCF was combined with an adjustable image-plane aperture pinhole, in order to separate the H2 rotational Raman bands from the silica background signal and improve the sensitivity down to a limit of detection (LOD) of 4.7 ppm (for only 26 fmol H2). The ability to monitor the levels of H2 and CH4 in a positive @entity1353 ( @entity1353 ) was demonstrated. The @entity14782 sensor possesses a high dynamic range (   5 orders of magnitude) with a fast response time of few seconds and provides great potential for miniaturization. We foresee that this technique will pave the way for fast, noninvasive, and painless point-of-care diagnosis of @entity209 in exhaled @entity1 breath.
