Fourier-transform infrared spectroscopy is a technique used to obtain an infrared spectrum of absorption of a solid, liquid or gas. An FTIR spectrometer simultaneously collects high-resolution spectral data over a wide spectral range. The term Fourier-transform infrared spectroscopy originates from the fact that a Fourier transform (a mathematical process) is required to convert the raw data into the actual spectrum.

The obtained infrared spectra contain signals (peaks) that can be assigned to characteristic vibrational-rotational structures of molecules and thus reveals information about the chemical nature of the investigated samples. Moreover by spectra comparison with database single substances can be identified in many cases.