Muhammad Sarfraz Arshad

Compound identification by Raman spectrum is carried out by comparing its spectrum with the spectrum of a standard sample, registered on the same device under the same conditions.Quantification is carried out using known quantities or concentrations of a standard sample.Quantitative analysis is based on direct proportional the dependence of the intensity (I) of the spectral lines to the number of molecules (N) per unit volume.

Sepman, A. V., V. V. Toro, A. V. Mokhov, and H. B. Levinsky. "Determination of temperature and concentrations of main components in flames by fitting measured Raman spectra." Applied Physics B 112, no. 1 (2013): 35-47.

I agree with Dr. Yuri Mirgorod

For Raman spectroscopy, quantification of concentration in a multiphase sample requires some standard data. In multiphase samples, due to interactions, the peak might shift to lower or higher wavenumber, change its intensity as well as develop some asymmetry in it, leads to the Fano resonance and BWF peak-profiles.

There are standard ways to fit the data with deconvoluted Lorentzian peaks. However if you do not have sufficient reference data, or the interactions are complex or in the composite some selection rules are compromised, you may get erroneous results.

I'll personally recommend three techniques for such quantitative assessment: (1) XPS, (2) Rietveld refinement of XRD data, (3) EDAX. The first and third are more suitable for probing surface properties, whereas the second is good for measuring bulk information.