Detail of an IR spectrum

Infrared Spectroscopy

While Infrared (IR) spectroscopy is most often used for the characterisation of organic molecules, it can also be applied to inorganic materials. IR Spectroscopy utilises the fact that IR radiation can excite molecular structures to different vibrations. This excitation leads to the absorption of characteristic bands of the irradiating IR light. The resulting IR spectrum makes it possible to identify compounds and, with the use of references, quantify them with detection limits between 0.1 and 1%.

Modern Fourier Transform Infrared spectrometers (FTIR) irradiate the sample with a wide spectrum of IR radiation with wavelengths in the range of 2 to 50 µm. They enable analyses with a high time resolution and a good signal to noise ratio. The signal consists of the transmitted IR light or, in the case of samples that are non-transparent for IR, the reflected IR light. The information depth is between 3 and 0.1 µm and the lateral resolution is between 0.1 and 1 mm. The requirements for the samples are minor, since the method works under atmospheric conditions. Inorganic and organic materials can be analysed as solids (smooth or powders), gases or liquids.

Synonyms / Related Techniques

  • ATR-FTIR (Attenuated Total Reflection Fourier Transform Infrared Spectroscopy)

Case Studies