Towards a Miniaturized Photoacoustic Detector for the Infrared Spectroscopic Analysis of SO 2 F 2 and Refrigerants.

Sulfuryl fluoride (SO 2 F 2 ) is a toxic and potent greenhouse gas that is currently widely used as a fumigant insecticide in houses, food, and shipping containers. Though it poses a major hazard to humans, its detection is still carried out manually and only on a random basis. In this paper, we present a two-chamber photoacoustic approach for continuous SO 2 F 2 sensing. Because of the high toxicity of SO 2 F 2 , the concept is to use a non-toxic substituent gas with similar absorption characteristics in the photoacoustic detector chamber, i.e., to measure SO 2 F 2 indirectly. The refrigerants R227ea, R125, R134a, and propene were identified as possible substituents using a Fourier-transform infrared (FTIR) spectroscopic analysis. The resulting infrared spectra were used to simulate the sensitivity of the substituents of a photoacoustic sensor to SO 2 F 2 in different concentration ranges and at different optical path lengths. The simulations showed that R227ea has the highest sensitivity to SO 2 F 2 among the substituents and is therefore a promising substituent detector gas. Simulations concerning the possible cross-sensitivity of the photoacoustic detectors to H 2 O and CO 2 were also performed. These results are the first step towards the development of a miniaturized, sensitive, and cost-effective photoacoustic sensor system for SO 2 F 2 .