Infrared (IR) Spectrophotometers
Molecules are able to absorb electromagnetic energy in the Infrared (IR) region of the electromagnetic spectrum. The IR radiation has the appropriate level of energy to excite vibrational movement of molecular bonds. Each type of bond, between the different atoms, will absorb the IR radiation and begin to vibrate at slightly different frequencies from one another. This phenomenon can be utilized to examine various molecules by observing the different vibrational signals.
An IR spectrophotometer, shown in the picture, is an instrument which is designed to obtain an infrared spectra of a molecule. An IR spectrum is obtained by first irradiating a sample with an IR source of light. The light passes through the sample, which can be in solution or contained within a salt plate, and then onto an IR light detector. The spectrum is analyzed by examining at which frequency the peaks occur. Different peak frequencies indicate different type of vibrational motion and hence, different types of chemical bonds. The peak intensities are usually denoted as percent transmittance (%T), which compares the amount of light absorbed compared to the amount of IR light that was not absorbed. The frequencies are normally listed in wave numbers (in units of reciprocal centimeters).
Acquired in January 2006, the Nicolet 6700 represents an upgrade in both resolution and wavelength coverage. The instrument is capable of high resolution (0.125 cm-1) in the mid and near IR regions. Attenuated total reflectance (ATR) accessories are used to conveniently analyze a wide range of materials. In addition a chemometric software package will result in an increased ability to use this spectrometer for quantitative applications.
We also have two Thermofisher IR100 FTIR instruments (purchased 2006) which are housed in the sophomore teaching laboratories.