AUTOMATED DETECTION OF ACETONE, METHYL ETHYL KETONE, AND SULFUR-HEXAFLUORIDE BY DIRECT ANALYSIS OF FOURIER-TRANSFORM INFRARED INTERFEROGRAMS

The lack of a valid background reference spectrum for many Fourier tra nsform infrared (FT-IR) spectrometric open-air monitoring applications limits the ability to perform quantitative measurements. Direct inter ferogram analysis suppresses the broad-band detector envelope and main tains the spectral signature of interest to circumvent this limitation . The background suppression approach uses a combination of interferog ram segment selection, digital filtering, and pattern discrimination t echniques. The spectral band location, width, and contour of the vapor determine the parameters necessary for background suppression. Interf erogram segment selection relies principally on the spectral bandwidth . Digital filter design employs inputs of both spectral band location and width. Pattern discrimination methods consider the variation in th e spectral band contour with band intensity. FT-IR spectrometer measur ements from both laboratory and open-air trials demonstrate the utilit y of the background suppression approach with analytes of acetone, met hyl ethyl ketone (MEK), and sulfur hexafluoride (SF6).