Quartz-Enhanced Photoacoustic Spectroscopy-Based Acetone and Ammonia Measurements from Human Breath Near 8 μm Wavelength Band

Human breath gas analysis is a noninvasive disease diagnostic approach used to identify different pathological conditions in the human body. Monitoring breath acetone (C₃H₆O) and ammonia (NH₃) as biomarkers is vital in diagnosing diabetes mellitus and liver disorders, respectively. In this article, the quartz-enhanced photoacoustic spectroscopy (QEPAS) technique is proposed and demonstrated for measuring C₃H₆O and NH₃ in human exhaled breath samples. We present the QEPAS technique-based approach combined with a broadband tunable quantum cascade laser (QCL) operating from 7.9 to 8.4 μm to target both C₃H₆O and NH₃ at specific absorption wavelengths. The experimental results show that minimum detection limits (MDLs) of 57 and 190 ppb were achieved for C₃H₆O and NH₃, respectively. The proposed technique measured C₃H₆O and NH₃ biomarkers in human breath samples collected from volunteers. The concentration measurements of exhaled breath biomarkers using the QEPAS technique in the 8 μm spectral region agreed with the blood glucose and blood ammonia measurements. The measurement limit and sensitivity met the requirement of the breath gas analysis needed to distinguish the concentrations obtained from a healthy person from those of a person with diabetes and liver disorder conditions.