Quantitative Fourier-Domain Analysis. Part I: Analysis of Raw FT-IR Interferograms

Abstract

A new procedure for performing quantitative analysis in the Fourier domain has been developed. The procedure involves the use of a linear, recursive digital filter for the analysis of raw interferogram data from a Fourier transform infrared (FT-IR) spectrometer. It was discovered that the analysis of raw interferograms permitted the use of spectral information that is generally neglected when conventional quantitative Fourier-domain procedures are used. Furthermore, a significant reduction in the computation requirements for Fourier-domain quantitative analysis procedures is seen. It was also discovered during the analysis of the raw interferograms that instrument stability was one factor which affected the accuracy of the concentration estimates. Tests were performed to demonstrate the required stability of the instrumentation, and a procedure is described for maintaining the required instrument stability throughout the analysis. Once instrument stability was achieved, the quantitative results which were obtained were similar to results obtained from the conventional Fourier-domain analysis algorithms.