Selective Detection of HFC and HCFC Refrigerants Using a Surface Acoustic Wave Sensor System

Halogenated hydrocarbons are the generic base of most refrigerants. They are known to be greenhouse gases; some of them are even suspected to have an ozone depleting potential. Thus, an urgent need exists to detect and identify these compounds. However, refrigerants usually have very low boiling points as well as low electrochemical activities. The latter problem is a serious obstacle to the development of appropriate electrochemical sensors. It is circumvented by using mass sensitive methods of detection. To solve the former problem, the analytical system has to be optimized with regard to effective collection and detection of the refrigerants. In this work, a system for detection and identification of refrigerants is presented, based on a surface acoustic wave sensor array. The system is using a two-step analyte preprocessing unit containing a molecular sieve filter to minimize humidity and a carboxen trap for preconcentration of the analytes. Refrigerants R22, R134a, and R507 have been selected for analysis. The respective detection limits of 10, 20, and 50 ppm indicate the system is useful for leak detection in air conditioning and refrigerating systems, surveillance of exposure limits, etc.