The applicability of IR spectra to samples is quite extensive, the solid, liquid or gaseous samples can be used, inorganic, organic and macromolecule compounds can be detected. In addition, the infrared spectrum has the characteristics of rapid testing, convenient operation, good repeatability, high sensitivity, low sample dosage and simple structure, so it has become the most common and indispensable tool for modern structural chemistry and analytical chemistry. Infrared spectroscopy has been widely used in the fields of structure, conformation and mechanical properties of polymers as well as physics, astronomy, meteorology, remote sensing, biology, medicine and so on.
The position and intensity of IR absorption peaks reflect the characteristics of the molecular structure, which can be used to identify the structural composition of unknown objects or to determine their chemical groups, while the absorption intensity of the absorption bands is related to the content of chemical groups, which can be used for quantitative analysis and purity identification. In addition, IR spectra also play a role in the study of chemical reaction mechanism. But the most widely used is the structure identification of unknown compounds.