Mid-infrared spectroscopy (MIR) is a vibrational spectroscopy technique that identifies chemicals based on the interaction of molecules with electromagnetic radiation in the mid-infrared region (400-4000 cm-¹). Infrared spectroscopy identifies chemicals based on the absorption of specific wavelengths of mid-infrared light by a molecule. Molecular absorbances of mid-infrared light cause molecular rotations and vibrations and are classified by chemical functional groups. The resulting MIR spectrum produced is characteristic for a given molecule. Attenuated total reflection (ATR-MIR) is the most popular sampling technique used in most laboratories today, and allows for the fast analysis of solid and liquid materials. MIR spectra can be searched against large reference spectral databases, making this technique a powerful tool for identification of chemical unknowns.

Instruments are available in a variety of form factors.  The most common are benchtop instruments, but a growing number of manufacturers have released portable and handheld models.  The technique is mature with a large number of companies having MIR instruments on the market.  There is a wide range of prices depending on form factor and other capabilities.   Typical cost is on the order of $20,000-$100,000.