What are the tires of your car and the soles of your shoes made of? If you thought of rubber, you were thinking of one of many products that would not exist as it does today without infrared spectroscopy. Infrared (IR) spectroscopy is a way to measure characteristic vibrations of molecules, making it one of the most popular techniques in chemistry for the last 45 years.
Infrared spectroscopy entered into widespread use after the government utilized the technique with great success for large-scale production of synthetic rubber during World War II.
Introduction to IR Spectroscopy
Infrared spectroscopy measures the vibrations of molecules. Each functional group, or structural characteristic, of a molecule has a unique vibrational frequency that can be used to determine what functional groups are in a sample. When the effects of all the different functional groups are taken together, the result is a unique molecular "fingerprint" that can be used to confirm the identity of a sample.
Sample
Spectrum: Butadiene
Butadiene was the essential chemical ingredient of the synthetic rubber program during World War II. Butadiene molecules were linked in long polymer chains to produce synthetic rubber. Knowing the concentration and purity of butadiene was essential to controlling rubber quality, and infrared spectroscopy was the only technique that could accurately gauge these properties.
Finding the concentration and purity of hydrocarbons is only the very tip of what infrared spectroscopy can do. Because of
its versatility and convenience, IR spectroscopy is now an essential in almost every branch of chemistry.
Landmark Instrument: Perkin-Elmer 21
The Perkin-Elmer 21 was the first commercially successful dual-beam infrared spectrometer. Its introduction came after several technological hurdles, but the PE 21 allowed scientists to take high resolution IR spectra quickly and reproducibly for the first time, ushering in a new era in chemical analysis and identification.
Click here or the picture for more information about the history of the Perkin-Elmer 21.
The dual-beam system and chart recorder of the Perkin-Elmer 21 made infrared spectrometry a viable method for chemical analysis. Compared to the single-beam optics and cantankerous behavior of the PE 12, its predecessor, the PE 21 was revolutionary.
Click here to learn how the Perkin-Elmer 21 works.
With the introduction of Fourier Transform IR spectrometry (FT-IR), IR instruments were suddenly able to produce better spectra in less time than ever before. This technology, as well as a few other improvements, are found in almost every modern IR instrument.