Quartz-enhanced photoacoustic spectroscopy (QEPAS) and Beat Frequency-QEPAS techniques for air pollutants detection: A comparison in terms of sensitivity and acquisition time
Biao Li, Giansergio Menduni, Marilena Giglio, Pietro Patimisco, Angelo Sampaolo, Andrea Zifarelli, Hongpeng Wu, Tingting Wei, Vincenzo Spagnolo, Lei Dong
Abstract
In this work, a comparison between Quartz Enhanced Photoacoustic Spectroscopy (QEPAS) and Beat Frequency-QEPAS (BF-QEPAS) techniques for environmental monitoring of pollutants is reported. A spectrophone composed of a T-shaped Quartz Tuning Fork (QTF) coupled with resonator tubes was employed as a detection module. An interband cascade laser has been used as an exciting source, allowing the targeting of two NO absorption features, located at 1900.07 cm−1 and 1900.52 cm−1, and a water vapor absorption feature, located at 1901.76 cm−1. Minimum detection limits of 90 ppb and 180 ppb were achieved with QEPAS and BF-QEPAS techniques, respectively, for NO detection. The capability to detect multiple components in the same gas mixture using BF-QEPAS was also demonstrated.