A comparative study and trace- level detection of volatile organic biomarkers using UV-IR-THz sources based high -Q helmholtz photoacoustic sensor.

This paper reports the trace-level detection of volatile organic compounds (VOCs) like methanol, ethanol, and isopropanol, which are biomarkers for various diseases like diabetes, breast cancer, lung cancer, chronic pulmonary diseases, squamous cancer, cystic fibrosis, chronic liver diseases, chronic kidney diseases and so on. Here, the photoacoustic spectroscopy technique was used for the trace-level detection of these biomarkers using an indigenously designed tunable frequency (1.4 to 4 kHz range) Helmholtz photoacoustic (PA) cell. The study was carried out with UV (266 nm), Mid IR (5.4-7.3 µm) and THz (0.11 THz) range sources to explore and compare the PA signal generated by mentioned samples for different electronic vibrational and rotational level excitations. We achieved a low detection limit (LoD) of the order of 39.3 ppbV, 29.7 ppbV, and 11.6 ppbV for methanol, ethanol, and isopropanol, respectively using this non-invasive cost-effective, and fast technique. In addition, THz-based PA signal for these samples is reported for the first time.