We present an empirical model for the cross-section of low concentration acetone gas in the range of 1671.5–1675 nm that encompasses the absorption band of the methyl stretch overtone. This model is experimentally validated with cavity ring-down spectroscopy (CRDS) measurements performed with a calibration gas and its diluted mixtures with breath samples. Particular attention is paid to accurate wavelength measurements with an interferometric wavemeter. The theoretical framework for analysis of gas mixtures with several absorbing species is presented. We show that the proposed empirical model can be used to accurately determine the concentration of acetone vapor in human breath samples. The comparison of the acetone absorption cross-section with previous results is also presented.

This study utilizes continuous wave cavity ring-down spectroscopy (CW-CRDS) at a wavelength approximately 1672 nm to detect acetone and methane in exhaled human breath. We employed a commercial distributed feedback diode laser (DFB), which delivered approximately 4 mW of power across a tuning range of 3.5 nm to measure acetone and methane concentrations in exhaled human breath. A detection limit of about 10.5 parts per billion (ppb) was demonstrated. Samples were collected from two distinct population locations, 23 individuals from Doha, Qatar, and 19 volunteers from College Station, Texas. The content of multiple gas mixture components was determined. The developed method for retroactive determination of the laser tuning eliminated the need for online wavelength determination. Simultaneous measurements of acetone and methane in exhaled breath can assist in diagnosing and monitoring diabetes and in assessing metabolic profiles of individuals using this noninvasive technique.