Fourier Transform near Infrared Absorption Spectroscopy of Gases

The application of Fourier transform near infrared spectroscopy (FT-NIR) to the analysis of gas phase molecules is presented. The use of this technique with both sealed laboratory cells and open-path measurements is demonstrated. The gas phase absorption spectra of several environmentally important organic molecules were collected for qualitative comparison. Calibration data and detection limits for several of the compounds are presented. For ammonia, the background equivalent concentration for a 10 cm path was determined to be 1.5 ppm while propane in the same pathlength was found to be 180 ppm. Other applications of this technique, including the use of fibre optics for remote sensing, are also discussed.