A sample is illuminated with infrared light, the absorption of which causes molecular vibrations in the sample. These vibrations are characteristic of functional groups in the sample. A representative spectrum is shown to the left with some of the evident functional groups denoted. FTIR is not able to determine connectivity of functional groups.

FTIR-ATR is capable of determining the major organic chemical species present in a sample, with a detection limit of 1-5% by weight. FTIR-GA is used for analyzing monomolecular layers on a reflective surface.

DTGS detector for routine ATR analysis

MCT detector for improved signal-to-noise ratio for GA

KBr beamsplitter