Interest in organophosphorus compounds has been accelerated by their usefulness as insecticides, oil additives, plasticizers, and stabilizers. Common to most of these compounds is the phosphoryl group. The infrared absorption of this group may be used to give information concerning the composition of these compounds.
Jerome Goldenson, "The Phosphoryl Doublet in Infrared Spectra of Organic Phosphorus Compounds as an Index of Purity," Appl. Spectrosc. 18, 155-157 (1964)