Abstract
A breath analysis system based on ultraviolet-absorption spectroscopy was developed by using a hollow optical fiber as a gas cell for real-time monitoring of isoprene in breath. The hollow optical fiber functions as an ultra-small-volume gas cell with a long path. The measurement sensitivity of the system was evaluated by using nitric-oxide gas as a gas sample. The evaluation result showed that the developed system, using a laser-driven, high-intensity light source and a 3-m-long, aluminum-coated hollow optical fiber, could successfully measure nitric-oxide gas with a 50 ppb concentration. An absorption spectrum of a breath sample in the wavelength region of around 200–300 nm was measured, and the measured spectrum revealed the main absorbing components in breath as water vapor, isoprene, and ozone converted from oxygen by radiation of ultraviolet light. The concentration of isoprene in breath was estimated by multiple linear regression. The regression analysis results showed that the proposed analysis system enables real-time monitoring of isoprene during the exhaling of breath. Accordingly, it is suitable for measuring the circadian variation of isoprene.
Highlights
Breath analysis has attracted a lot of attention because it can noninvasively monitor the early stages of disease states [1,2]
Besides major compounds such as nitrogen, oxygen, carbon dioxide, and water, human breath gas contains various components, including inorganic gases such as nitric monoxide and carbon monoxide [3,4], and volatile organic compounds such as acetone and isoprene [5], and it is known that these minor components reflect the internal metabolism
Large-scale gas chromatography–mass spectrometry (GC-MS) systems have been commonly used for the analysis of such trace gases [6,7,8]
Summary
Breath analysis has attracted a lot of attention because it can noninvasively monitor the early stages of disease states [1,2] Besides major compounds such as nitrogen, oxygen, carbon dioxide, and water, human breath gas contains various components, including inorganic gases such as nitric monoxide and carbon monoxide [3,4], and volatile organic compounds such as acetone and isoprene [5], and it is known that these minor components reflect the internal metabolism. A simple breath-analysis system based on UV-absorption spectroscopy with a hollow-optical-fiber gas cell is proposed. This system achieves highly sensitive measurement at low cost owing to its high-intensity, broad UV light source and hollow optical fiber gas cell. Its sensitivity is improved by using long hollow fiber cells so that it can quantitatively measure the isoprene concentration in human breath
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