Friday, November 22, 2019

Why KBr used in IR spectroscopy

Infrared spectroscopy is a useful method to identify the functional groups of sample materials. A sample can be in solid, liquid, and gaseous states and can be analyzed by IR or FTIR spectroscopy with the sample as a transmission technique from radiant light interaction. A solid sample type is a typical sampling technique for the study of IR transmission spectroscopy. This involves preparing a solid sample in the form of a potassium bromide (KBr) disk or pellet (7 mm or 13 mm) to properly mount the sampling area of ​​an infrared spectrophotometer.
Pellet preparation is a significant factor for IR spectroscopy it has to be transparent so that it allows to pass of IR radiations through them. So to get the precise IR spectrum of a sample with good intensity, sharp peaks with high resolution, salts such as potassium bromide (KBr), sodium chloride (NaCl), and Silver chloride (AgCl) are used for the mixing of the sample.
KBr is commonly used as a window material or in pellet preparation as a carrier of the sample in the ratio of 1:100 since it is optically transparent for the light in IR between 4000–400 cm-1. KBr is commonly used in infrared spectroscopy because there is an alkyl halide and no alkyl halide shows any absorption in the region of infrared and is chemically inert and robust.


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