I have synthesized a polymer with dextran and in FTIR spectra. There are many peaks which are related to different molecular bonds in polymer structures. And a specific peak (such as a peak in 2500 nm-1) in two FTIR tests has different peak intensities. I would like to know if there are any differences between these two peaks?
To put it simply, if you see a peak intensity increase, then you have more of that particular type of bond. You need to make sure that the peak position is at the sample wavenumber. Any big shift in either direction tend to imply that some interaction has occurred.
One other thing to keep a note of, is whether the peak itself has gotten broader or not. If the peak shape is similar, then its pretty much just more of the particular type of bond. However if the peak has broadened, then it could mean that some interaction has occurred (usually hydrogen bonding interaction).
Relative abundance and strength of the dipolar change your the affected bond
To put it simply, if you see a peak intensity increase, then you have more of that particular type of bond. You need to make sure that the peak position is at the sample wavenumber. Any big shift in either direction tend to imply that some interaction has occurred.
One other thing to keep a note of, is whether the peak itself has gotten broader or not. If the peak shape is similar, then its pretty much just more of the particular type of bond. However if the peak has broadened, then it could mean that some interaction has occurred (usually hydrogen bonding interaction).
Indicates the presence of asymmetric stretching bond is a bond that has the most energy and unstable.
All aforementioned is so far correct. In the MIR the occuring bands typically correspond to particular functional groups and the peak intensity scales with transition dipole moment and bond density (in an abstract manner you may also call this "concentration"). Two additional comments from my side (a simple one and a more sophisticated one).
1) As long as we talk about absorbance spectra calculated from transmittance, the peak intensity would of course also scale with sample thickness (see Lambert-Beer's law).
2) The case that peak width changes was already shortly discussed above. In practice a broadening peak may often be understood in terms of higher disorder e.g. due to higher temperature, inhomogeneities or also strain. In case that you are not interested in these phenomena but just in the bond density, I would recommend to evaluate the integral of the band instead of only its height. In general integration is more accurate since simple band height evaluation is more sensitive to noise.
The intensity of the peak effected by Polarity of the molecule, fufunctional group
I agree with many of the points raised above. In addition, in complex mixtures of organic moleceiuls (e.g. serum), the peak wil be the sum of contributions of all molecules containing that dipole (organic bone vibration), and therefore the Beer Lembert law may not be simply applied fro an individual compound. In the case of complex mixture of organic solutes, a more complex spectral analysis strategy is usually required
@Jerry Pui Ho Li, Can you please send me the some reference paper on the peak height and broadness of peak in FTIR
Peak of any molecular signature is not a single value,always it come in a range. Your two peak might be in same range with different value.
Another option:
If you modify the same material,then earlier peak might shift to another position due to its different chemical behavior.
The intensity of the peak is an indication of relative abundance or concentration
the intensity of every peak shows the measuranig in changing of dipol moment
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