Near-infrared spectroscopy is analogous to mid-infrared spectroscopy (FTIR) by identifying chemicals based on the interaction of molecules with electromagnetic radiation in the near-infrared region (4000-10000 cm-1). NIR identifies chemicals based on the absorption of specific wavelengths of near-infrared light by a molecule, resulting in a spectrum that is characteristic for that molecule. NIR differs from mid-infrared spectroscopy in that the molecular absorbances are of higher-energy light, making the vibrations of the molecules of higher orders (i.e., combination and overtones) than that of mid-infrared.
Point analysis (“bench top”) systems are most often used for analyzing condensed phase materials. In the last two decades, “point and shoot” instruments (often configured like a gun) have come into vogue. These instruments make analyses of foods, pharmaceutical, and consumer products fast and able to be performed by technicians with minimal training. The resulting spectra can be searched against reference spectral databases for pure materials, but mixture analysis requires a chemometric approach configured by an expert spectroscopist.