A team from the University of Bari in collaboration with Alpes Lasers uses a QC-XT laser combined with a quartz-enhanced photoacoustic spectroscopy setup to measure carbon monoxide (CO), nitrous oxide (N2O), carbon dioxide (CO2), and water vapor (H2O) simultaneously. The device emission wavelengths ranged from 2100 cm-1 to 2250 cm-1 and the achieved minimum detection limits were 6 ppb, 7 ppb, and 71 ppm fr CO, N2O, and CO2, respectively, at 100 ms of integration time.

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/12021/120210E/Quartz-enhanced-photoacoustic-spectroscopy-employing-a-Vernier-effect-distributed-feedback/10.1117/12.2607866.short?SSO=1