Effect of Resolution on Quantification in Open-Path Fourier Transform Infrared Spectrometry under Conditions of Low Detector Noise. 1. Classical Least Squares Regression

The effects of resolution, spectral window, and background type on the predictive ability of classical least squares regression (CLS) on spectra measured by an open-path Fourier transform (OP/FT-IR) spectrometer were tested in some detail. It is shown that the most accurate quantitative results are obtained by using equidistant backgrounds, reduced spectral windows, and low resolution. The effect of interfering compounds is shown to be particularly serious when CLS regression is used to process OP/FT-IR spectra.