In FTIR analysis, I am getting single peak of same intensity at same wave number for three compounds i.e. CTAB, sodium salicylate (NaSal) and mixture of CTAB+NaSal in aquous media. Peaks are overlapped to each other. How is it possible if both CTAB and NaSal are different compound? 1000 ppm is taken for FTIR analysis. What would be the possible reason? Is it due to the higher concentration (1000 ppm) or something else?
Just that I understand you right, you have three different aqueous solutions, namely CTAB, NaSal, and their mixture, all three with a molar ratio of 1:1000, right? And you see no difference in the infrared spectra for all three solutions? My guess would be that you see in all three cases nothing but the water peaks. Compare your spectra e.g. with this spectrum: https://i.stack.imgur.com/1RcQI.png
Dear Prof. Thomas Mayerhöfer .
Thank you for the kind response.
That's absolutely true. These peaks corresponds to the water peaks.
Is it due to the lower concentration of solid (NaSal or CTAB) in water ? since I have taken 1000 ppm. Is there any criteria of detection limit of FTIR?
My pleasure! The problem is that water has very strong absorptions, much stronger than most functional groups of organic materials, which also overlap with the latter. My feeling is that even 10000 ppm would not suffice to see differences - probably you would have to increase the concentration to up to 10 % or even more...
This shows for example a concentration dependence of gelatin in water, using ATR - FTIR
"Improved Protocols for Vibrational spectroscopic analysis of body fluids", Franck Bonnier, François Petitjean, Matthew J. Baker, Hugh J. Byrne, Journal of Biophotonics, 7, 167-179 (2014)
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials Chemistry
- Polymer Chemistry