Fourier Transform Infrared Spectroscopy (FTIR) Principle

Fourier Transform-Infrared Spectroscopy (FTIR) is an analytical technique used to identify organic (and in some cases inorganic) materials. This technique measures the absorption of infrared radiation by the sample material versus wavelength. The infrared absorption bands identify molecular components and structures.
When a material is irradiated with infrared radiation, absorbed IR radiation usually excites molecules into a higher vibrational state. The wavelength of light absorbed by a particular molecule is a function of the energy difference between the at-rest and excited vibrational states. The wavelengths that are absorbed by the sample are characteristic of its molecular structure.


FTIR analysis became the main used technique when specific analytical topics have to be addressed, mainly when non-destructive analysis is needed. In this respect, according to our opinion, challenging analytical issues are raised in two important cases; the first one is that when historic (archaeological) or artistic materials have to be analyzed while the second issue came from the analysis of highly- specific biomaterials

The FTIR spectrometer uses an interferometer to modulate the wavelength from a broadband infrared source. A detector measures the intensity of transmitting or reflected light as a function of its wavelength. The signal obtained from the detector is an interferogram, which must be analyzed by a computer using Fourier transforms to obtain a single-beam infrared spectrum. The FTIR spectra are usually presented as plots of intensity versus wavenumber (in cm-1). Wavenumber is the reciprocal of the wavelength. The intensity can be plotted as the percentage of light transmittance or absorbance at each wavenumber


• Identification of foreign materials

  • Particulates
  • Fibers
  • Residues
    • Identification of bulk material compounds
    • Identification of constituents in multilayered materials
    • Quantitation of silicone, esters, etc., as contamination of various materials