Simultaneous detection of ammonia, methane and ethylene at 1.63 ìm with diode laser photoacoustic spectroscopy

Spectral investigation around 6115 cm-1 for simultaneous detection of ammonia, methane and ethylene in gas samples is presented. New experimental data on the í2+í3+í4 combination band of ammonia are reported with a resolution of 1.5 GHz. A trace gas analyzer based on a resonant photoacoustic cell and an external cavity diode laser has been used for detection. A data fitting procedure has been developed in order to improve the system sensitivity and to limit the need of a reference cell. The selected spectral region allows a sensitivity of about 30 ppm for ethylene, 6 ppm for methane and 60 ppm for ammonia with 0.3mW laser power. An application of simultaneous detection of these molecules in a mixture simulating a real gas sample from biomass gasification product is discussed.