You may compare the band's intensity and correlate it with the concentration. In this process, some peaks may be disappeared, or intensity may be decreased. IR intensity is directly proportional to the concentration, and you may use PLS to get an accurate concentration profile from the spectrum. If you have spectra with reference degrees of DDA, it will be easier.

Sergey Mamedov I would be a little more cautious. Beer's law is a limiting law, which can be derived under certain approximations from the Lorentz-Lorenz relation. Accordingly, only for very weak absorptions, it will be found that peak absorbance is proportional to the concentration - a C=O band, e.g., may already be too strong. Depending on the method, further physical restrictions may apply. The full story can be found e.g. in Article The Bouguer-Beer-Lambert Law: Shining Light on the Obscure

Mr. Kumaresan,

There are a set of references detailing quantification by vibrational spectroscopies; both IR- and Raman methods, including by conventional and polarized approaches to these methods.

For instance, there are references [1-4]. The chemometric data processing has been comprehensively discussed, with respect to different statistical methods, thus indicating the accuracy and the precision of the quantitative data. Reference [3] provides even experimental dataset.

[1] Talanta, 69 (2006) 822-828

Validation of reducing-difference procedure for the interpretation of non-polarized infrared spectra of n-component solid mixtures

Bojidarka B.Ivanova, Dimiter L.Tsalev, Michail G.Arnaudov

[2] A quantitative solid-state Raman spectroscopic method for control of fungicides

Bojidarka Ivanova, Michael Spiteller

Analyst, 2012,137, 3355-3364

[3] https://zenodo.org/record/2248038#.X-hM0NBKiUk

[4] On the capability of the linear dichroic infrared spectroscopy, Bojidarka Ivanova

ISBN: 6139957893, 2018, pp. 72, Lap Lambert Academic Publishing