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

• Published in: Sensors (Basel, Switzerland) Vol. 23; no. 1
• Main Authors: Yassine, Hassan, Weber, Christian, Brugger, Nicolas, Wöllenstein, Jürgen, Schmitt, Katrin
• Format: Journal Article
• Language: English
• Published: MDPI AG 01.12.2022
• Subjects: Air pollution; Detectors; Global warming; Global warming potential; Infrared spectroscopy; Refrigerants; Germany
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s23010180

Sulfuryl fluoride (SO[sub.2]F[sub.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[sub.2]F[sub.2] sensing. Because of the high toxicity of SO[sub.2]F[sub.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[sub.2]F[sub.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[sub.2]F[sub.2] in different concentration ranges and at different optical path lengths. The simulations showed that R227ea has the highest sensitivity to SO[sub.2]F[sub.2] among the substituents and is therefore a promising substituent detector gas. Simulations concerning the possible cross-sensitivity of the photoacoustic detectors to H[sub.2]O and CO[sub.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[sub.2]F[sub.2].