This is the simplest and most basic of the infrared spectroscopic sampling techniques, although nowadays it is being replaced by attenuated total reflectance (ATR) which requires minimal sample preparation but has a small sampling depth which may over emphasise the contribution from the surface of a sample.

In transmittance the infrared radiation is passed through a sample and the transmitted radiation is measured. The spectra obtained will be representative of the whole of the volume sampled and 'localised' (e.g. surface) properties can quite easily be lost in the 'bulk' properties depending on the size and nature of the sample. It is only useful for thin (<10 µm) samples or when looking at weak bands, such as overtones, in thicker samples. Often sample preparation, such as the manufacture of KBr discs or Nujol mull preparation, is necessary which can be time consuming and difficult to reproduce.

For more information email MERI@shu.ac.uk or call MERI reception on 0114 225 3500