DIFFERENTIAL SPECTROPHOTOMETRIC ANALYSIS

Abstract

In differential spectrophotometric analysis, scans are made with the unknown and reference samples in the appropriate light paths of a double-beam spectrophotometer. The spectra obtained in this fashion yield the ratio of the transmittances or the difference between the absorbances of the two samples. Both the character and usefulness of the difference spectra depend on the choice of the reference samples. The paper develops the theroy for extracting analytical information from difference spectra. The equations derived for a two-component system suggest a number of alternate means of selecting the analytical and reference frequencies. General infrared methods which evolved naturally from these selections are discussed and illustrated with an example chosen purposely so that both components absorb throughout the analytical region.