KBr has a larger transmission window in the IR compared to NaCl

But for liquid samples we use NaCl cell sir

you can use a KBr cell instead. the sample composition is an important point for the material selection, e.g. NaCl and KBr are both not suitable for aqueous solutions

You can use KBr or NaCl only if your samples are hydrophobic, since these cell can be affected by samples soluble in water because KBr and NaCl are soluble in water and these cells can be broken. If you have hydrophilic samples you can use a ZnSe cell.

KBr, has a trnasmitance of 100 % in the range of wave number (4000-400 1/cm). Therefore, it does not exhibit absorption in this range.

Mr. Prakashbabu,

The materials should be transparent within the frame of the mid-IR region (5000 - 400 cm-1). And those are for KBr, exactly. For NaCl the characteristics 5000-600 cm-1.

Agree with all above eminent person's views.

KBr is used as a carrier for the sample in IR spectrum  and it is optically  transparent for the light in the range of IR measurement. So that no interference   in absorbence would occur.  

KBr, has a transmittance of 100 % in the range of wave number (4000-400 cm-1). Therefore, it does not exhibit absorption in this range . KBr has a larger transmission window in the IR compared to NaCl .

The KBr does not show any absorption spectrum in IR region because it has a 100% transmission window in the range of wave number (4000-400 cm-1) at the FTIR spectroscopy with electronegativity of 2.0 based on the Pauling scale.

https://www.researchgate.net/publication/44427401_Inorganic_chemistry_principles_of_structure_and_reactivity_James_E_Huheey_Ellen_A_Keiter_Richard_L_Keiter

Article Inorganic chemistry : principles of structure and reactivity...

Then why KBr pellets or any sample preparation method do not use in FT-NIR?

T. Jayatunga: in mid IR, the problem is usually too much absorbance by the sample, so that you need to make three path length small, either by dilution in a KBr pellet or coating a thin film in any IR transparent flat crystal.

In near IR (NIR), you have the opposite problem of not much absorbance so that you need a high path length. So usually you can observe the sample directly without KBr or any other special windows. A glass cuvette for example can work.

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.

Thank you very much for your answers.

Hello all!

Just happened to came across this question by coincidence and noticed one curious thing. No one - especially scientists - should blatantly plagiarize in order to achieve their purposes, in this case, to get a better score.

@ Zainab Raheem:

Next time you quote word-by-word something you've read, please give the proper credit; your answer was plagiarized from one of Shimadzu's white papers.

URL: https://www.shimadzu.com/an/ftir/support/ftirtalk/talk8/intro.html

Regards.

KBr are alkyl halide and does not show any absorption spectrum in IR region.

and has a transmittance of 100 % in the range of wave number (4000-400 cm-1).

the KBr is very good transmittance material about 100% in very large area in the IR region (4000-400) cm-1 and KBr is good carrier the sample under test D. Prakashbabu

so, meaning to say that the ATR method has transmission only in the range of 4000 to 600 cm-1?

Although KBr is more expensive than NaCl, KBr has some advantages over NaCl. By using KBr crystal the measurement is possible over the range of 4000-400cm-1. But the range for NaCl is 4000-650 cm-1. NaCl starts to absorb IR from 650 cm-1.

KBr has a transmittance of 100% in the range of wave number (4000-400).Therefore, It doesn’t show or exhibit absorption in this range.

KBr will have absorption in the region less than 400 nm so peak which appear for KBr wont interfere with the sample peak. how solvent is used in the UV the same way the KBr/NaCl can be used in IR.