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A recently introduced approach to photoacoustic detection of trace gases utilizing a quartz tuning fork (TF) as a resonant acoustic transducer is described in detail. Advantages of the technique called quartz-enhanced photoacoustic spectroscopy (QEPAS) compared to conventional resonant photoacoustic spectroscopy include QEPAS sensor immunity to environmental acoustic noise, a simple absorption detection module design, and its capability to analyze gas samples ∼1mm3 in volume. Noise sources and the TF properties as a function of the sampled gas pressure, temperature and chemical composition are analyzed. Previously published results for QEPAS based chemical gas sensing are summarized. The achieved sensitivity of 5.4×10−9cm−1W∕√Hz is compared to recent published results of photoacoustic gas sensing by other research groups. An experimental study of the long-term stability of a QEPAS-based ammonia sensor is presented. The results of this study indicate that the sensor exhibits very low drift, which allows data averaging over 3h of continuous concentration measurements. Architecture and practical implementation of autonomous QEPAS-sensor controller electronics is described. Future developments of QEPAS technique are outlined.
Kosterev et al. (Tue,) studied this question.
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