Fourier Transform Infrared Spectroscopy

A Fourier Transform Infrared (FTIR) Spectrometer is a device that gathers a wideband Near – Infrared (NIR) to Far Infrared (FIR) spectrum. Apart from a diffraction device, such as a lattice monochromator or spectrograph, FTIR spectrometers capture all frequencies equally. This characteristic is known as the Multiplexer or Felgett Effect.

Working Principle:

The Michelson Interferometry Experimentation Configuration is commonly used in FTIR. The interferometer is made up of a beam splitter, a static mirror, and a mirror that accurately translates to and fro. The beam splitter is comprised of distinct properties that absorb 50% of the radiation that hits it while reflecting another half. The beam splitter divides the radiation from the source into two beams. One beam passes to the fixed mirror by the beam splitter, while the other is thrown back to the reflecting surface via the beam splitter. The radiation is reflected in the beam splitter by the stationary and rotating mirrors. Similarly, 50% of the radiant energy is transferred, while the other half is reflected at the beam splitter, resulting in just one beam passing to the detector and the second back to the source.

FTIR Uses:

  • Identifying unfamiliar substances.
  • To provide information when used in combination with other equipment such as TGA, GC, or Rheometer.
  • Kinetic data from the rise or decay of infrared absorptions.
  • Quantitative data, such as additives or pollutants.


  • What is FTIR spectroscopy? (n.d.). MilliporeSigma | United States. Retrieved June 11, 2022, from https://www.sigmaaldrich.com/NL/en/technical-documents/technical-article/analytical-chemistry/photometry-and-reflectometry/ftir-spectroscopy

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