For date palm leaves, FTIR analysis revealed peaks ranging from 4000 to 2800, one of which is extremely close to 4000. (3982) and transmitted more than 80%. Which of the functional groups represents these peaks?
with a note when plants are exposed to salt stress, some of these peaks disappear.
Thank you to everyone who can help.
1. https://www.ifsc.usp.br/~lavfis2/BancoApostilasImagens/ApLuminescencia/Infrared%20Spectroscop1.pdf , said, O-H, group.
2. http://www.thermoscientific.com/content/dam/tfs/ATG/CAD/CAD%20Documents/Application%20%26%20Technical%20Notes/Molecular%20Spectroscopy/FTIR/FTIR%20Spectrometers/XX51346-E-0215M-OrganicFunctionalChart.pdf said Amine group
*edit* after having read Hatsuo's answer, I completely agree with him. That peak at 2362 is surely CO2.
2858 and 2917 are C-H sym and asym stretch
the broad peak at 3394 is O-H stretch
Above that, there are no signals, only noice, to the best of my knowledge.
try:
https://www.science-and-fun.de/tools/
https://www.sigmaaldrich.com/DE/de/technical-documents/technical-article/analytical-chemistry/photometry-and-reflectometry/ir-spectrum-table
(the software KnowItAll gives no suggestion above O-H stretch as well)
3394 peak is an O-H stretch by water molecules
2858 peak is a C-H Symmetric stretch (aldehyde)
B. Srikanth Ragunath Martin Wortmann Akula Komuraiah thank you for your help
3600 peak is due to O-H bonding (non H bonded)
3000 to 3500 peak is due to O-H bonding (H bonded)
3300 peak is due to N-H bonding and also alkynes
3000 peak is due to C-H bonding
Usually, the Single bond region especially Hydrogen bonds lies between the wavenumbers 2500 to 4000.
The peaks will be sharp with strong intensity (Alkyne based)
The peaks will be broad with strong intensity (Alcohol-based)
Kindly refer to Silverstein Book on IR Spectroscopy for further details and references
Thanks and regards
Although you did not indicate what sampling method you used, it appears that you used KBr pellet method by grinding the leaves. If so, you may have had relatively large particles unevenly dispersed in the KBr and FTIR spectrum shows the sign of saturation. This is reflected by the peak contour of strong absorptions (they are not Gaussian or Lorenzian). As such, very weak bands, usually difficult to observe, might show up. The minimum transmission is around 20%, despite my statement of saturation. This is because, you have a thick, highly infrared absorbing particle through which IR is extremely strongly absorbed and have near zero transmission in the strong absorption frequency, whereas there are places that no leave particle covers and only KBr powder exists through which IR leaks to the detector. Thus, the 20% transmission line is effectively the 100% absorption line. If this happens, usually unobservable overtone and combination bands can also be observed. The very weak bands in the range of 4000 - 3700 cm-1 are very likely those non-normal modes. Another possibility along with these actual absorption is the noise. At this frequency range, the energy level of the IR source is very weak and noise is amplified. To distinguish noise from these overtone and combination bands is to take spectra multiple times and compare. Noise is not reproducible but weak overtone and combination bands are reproducible. I do not believe those bands are due to the OH band with free of hydrogen bonding.
To reduce those bands in the range of 4000 - 3700 cm-1, you can dry the leaves carefully and grind much more so that the particle size of your leaves is much smaller than the current sample. The newly obtained spectrum should show sharpening of all the strong bands in the range 1800-1000 cm-1 and weaken the intensity of weak bands in the rage 4000 - 3700 cm-1. This is a strong support if what I said above on spectral saturation is correct.
The bands at 3394 cm-1 is the hydrogen bonded OH stretch of the water molecules as well as -COH group of cellulose. 2918 cm-1 is the antisymmetric stretching band of CH2 and 2862 is the corresponding symmetric stretching band. 2362 cm-1 has nothing to do with your sample. It is carbon dioxide gas in your spectrometer. Maybe you did not properly purge the spectrometer and you used rather low resolution spectral collection conditions such as resolution of 8 cm-1. Ordinality, you will see nearly equal intensity doublet here at resolution of 2 or 4 cm-1. The peak shows some sign of split, though not as obvious as usual spectrum reported.
- Badges
- Science topic
- Similar topics
- Mathematics
- Algebra
- Matrix