Question
Asked 29th Mar, 2016

Why we use KBr in FTIR?

we use KBr pallet to record FTIR spectra, why dont we use other ionic crystals like NaCl.....

Most recent answer

14th Sep, 2021
Anika Tabassum Obonti
State University of Bangladesh
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.
1 Recommendation

All Answers (21)

29th Mar, 2016
Johannes Kiefer
Universität Bremen
KBr has a larger transmission window in the IR compared to NaCl
4 Recommendations
29th Mar, 2016
D. Prakashbabu
Reva University
But for liquid samples we use NaCl cell sir
29th Mar, 2016
Johannes Kiefer
Universität Bremen
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
1 Recommendation
31st Mar, 2016
Edwin A. Murillo
Universidad Francisco de Paula Santander
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.
3 Recommendations
7th Apr, 2016
Bojidarka B. Ivanova
Technische Universität Dortmund
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.
5 Recommendations
7th Apr, 2016
Niranjan Biswal
Rayagada Autonomous College (RAC)
Agree with all above eminent person's views.
7th Apr, 2016
Abbas Jassim Lafta
University of Babylon
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.  
2 Recommendations
29th May, 2017
Mohammed Ridha Al-Haideri
University of Babylon
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 .
 
 
1 Recommendation
9th Jun, 2017
Kasim Fawzy Ahmed
Salahaddin University - Erbil
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.
1 Recommendation
20th Oct, 2017
Thanuja Jayatunga
Industrial Technology Institute
Then why KBr pellets or any sample preparation method do not use in FT-NIR?
20th Oct, 2017
Kaoru Aou
Dow Chemical Company (Opinions are my own)
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.
2 Recommendations
20th Feb, 2019
Zainab Raheem
Baghdad University College of Science
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.
1 Recommendation
21st Feb, 2019
Thanuja Jayatunga
Industrial Technology Institute
Thank you very much for your answers.
9th May, 2019
Filipe Monteiro-Silva
University of Porto
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.
Regards.
2 Recommendations
5th Sep, 2019
Zainab Raheem
Baghdad University College of Science
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).
2 Recommendations
17th Dec, 2019
Jawdat Hilmi
Northern Technical University
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
1 Recommendation
17th May, 2020
Aranganathan Viswanathan
Indian Institute of Science Education and Research, Tirupati
so, meaning to say that the ATR method has transmission only in the range of 4000 to 600 cm-1?
17th Nov, 2020
Mohammad Hossain
University of Dhaka
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.
1 Recommendation

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