GENERATION OF SYNTHETIC BACKGROUND SPECTRA BY FILTERING THE SAMPLE INTERFEROGRAM IN FT-IR

The calculation of an absorbance spectrum depends on the measurement o f a blank, or background spectrum. In many cases, such as the determin ation of atmospheric constituents with the use of open-path Fourier tr ansform infrared spectroscopy (FT-IR) or the determination of water va por in a gaseous sample, it is very difficult to obtain a good backgro und spectrum. The difficulty is due to the fact that it is nearly impo ssible in these situations to measure a spectrum with no analyte featu res present. We present a method of generating a background spectrum b ased on filtering the analyte features from the sample spectrum. When the filtering method is used, the accuracy of the results obtained is found to be dependent upon the analyte peak width, peak height, and ty pe of filter employed. Guidelines for the use of this background gener ation technique for quantitative determinations are presented.