Infrared Spectroscopy (FT – IR / ATR)
| Instrument | Spectrum One, Perkin Elmer |
| Spectral Range | 4000 – 600 cm-1 |
| Materials | Organic solutions Aqueous solutions Neat solids or liquids Clippings, powders, etc. |
Spectral characterization based on chemical functional groups
Infrared (IR) Spectroscopy is used to identify functional groups in organic molecules. It is based on molecular vibrations such as stretching (which changes the bond length) and bending (which changes the bond angle). Vibrations resulting in no dipole moment changes are transparent by this measurement. When the incident light frequency matches one of the molecule’s vibrational modes of a molecule, a portion of the infrared radiation is absorbed while the rest is transmitted to the detector. The transmittance and/or absorbance as a function of frequency produces an infrared spectrum. The resulting spectrum creates a molecular fingerprint of the molecule and/or material. Different functional groups absorb and transmit different amounts of IR radiation based on the magnitude of their dipole moments. As a result, different functional groups produce bands in distinct regions of the IR spectrum and with distinct intensities. This feature allows for the practical detection and characterization of various functional groups.
Interpreting an IR spectrum may be performed by library matching from a spectral database, such as from NIST, or comparing band positions to reference tables. A selection of useful links are provided below: