Iterative least-squares fit procedures for the identification of organic vapor mixtures by Fourier-transform infrared spectrophotometry

Least-squares fitting (LSF) was applied to the qualitative analysis of IR spectra based on comparing standard reference spectra with the sample mixture spectrum. Identification of compounds in the sample was made by judging the fit level of the spectrum of each compound with the sample spectrum. An iterative procedure was developed to eliminate compounds with the worst fit levels in order to approach an optimal fit for the sample spectrum. The qualitative analysis results obtained from the optimal fit were further used for quantitative analysis.