why KBr is used in FTIR SPECTROSCOPY and why is it necessary
to triturate KBr during FTIR analysis?
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Answer Posted / bem nyax
This method exploits the property that alkali halides become plastic when subjected to pressure and form a sheet that is transparent in the infrared region. Potassium bromide (KBr) is the commonest alkali halide used in the pellets. Cesium iodide (CsI) may also be used to measure the infrared spectrum in the 400 to 250 cm-1 low-wavenumber region.
The preparation method for 13 mm-diameter pellets is described below. Approximately 0.1 to 1.0 % sample is well mixed into 200 to 250 mg fine alkali halide (the example of KBr is used below) powder and then finely pulverized and put into a pellet-forming die. A force of approximately 8 tons is applied under a vacuum of several mm Hg for several minutes form transparent pellets. Degassing is performed to eliminate air and moisture from the KBr powder. Inadequate vacuum may result in easily broken pellets that scatter light. Before forming the KBr powder into pellets, pulverize it to 200 mesh max. and then dry at approximately 110 °C for two to three hours. Note that rapid heating can oxidize some of the KBr powder to KBrO3, causing a brown discoloration. After drying the powder, store it in a desiccator.
When performing measurements, the background can be measured with an empty pellet holder inserted into the sample chamber. However, background measurements on a pellet holder with a pellet of KBr only, that contains no sample, can correct for infrared light scattering losses in the pellet and for moisture adsorbed on the KBr.
Reference >> http://www.shimadzu.com/an/ftir/support/ftirtalk/talk8/intro.html
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