Accurate Concentration Measurements Using Infrared Absorption without Determination of the Baselines

Abstract

Infrared absorption spectra have become widely used for in situ determination of concentrations in complex mixtures. However, experimental accuracy is often limited by lack of knowledge of the baselines. The mathematical treatment described below allows the spectra to be superimposed on any background with a shape as complex as a parabolic one. The concentrations are thus accurately determined whatever the baseline of the mixture spectrum and even those of the calibration spectra. A mathematical proof of this property is given within the framework of the presently used method, and tests of the efficiency of the method are presented.