A REFLECTOMETRIC SENSOR FOR AMMONIA AND HYDROCARBONS

Optical reflection measurements in the visible wavelength range may be used for fast analysis of changes in optical thickness of thin polymer layers caused by swelling of the film in contact with various gaseous analytes. Including an absorbing species into the sensitive layer, the applicability of this sensor can be extended to gases with acidic or basic character. The method is demonstrated using bromocresol purple as pH-indicator in a polydimethylsiloxane layer. Principal component analysis is used for qualitative analysis of a two-component gas.