Photoacoustic Spectroscopy in Trace Gas Monitoring

Gas phase spectroscopy is nowadays very common in a wide variety of fields next to chemistry and physics. From research involving living organisms to air pollution monitoring, spectroscopic gas sensors have proven to be indispensable tools. There are various ways of utilizing gas sensors, and each application has different demands. Some applications require a very high sensitivity for one specific gas compound, while others benefit more from sensors able to measure a wide range of gases. A high time resolution is also desirable, as well as selectivity, robustness, and little or no need for sample preparation. This paper discusses photoacoustic spectroscopy as a sensitive, on-line and non-invasive tool to monitor the concentration of trace gases. After a short introduction and a historic overview, attention is focused onto the description of devices and equipment; they determine the detection limits and selectivity. Applications are discussed with emphasis on environmental monitoring, medical applications and biological applications (such as post-harvest physiology, plant physiology, microbiology, and entomology).