I am a beginner at using FTIR (biologist by training, not a chemist) and would some appreciate some advice regarding sample analysis. I am attempting to characterise the profile of a drug vs lipid encapsulated drug.

The FTIR spectra of the drug is very distinct (Figure 1), however, this distinct spectra is notably absent from the spectra of lipid encapsulated drug (Figure 2).

I believe previous studies have had similar issues with nanoparticle encapsulation, where IR spectra of the drug showed superimposition to its parent materials, and may account for these results.

However, if I focus on the fingerprint region of the spectra, I have identified discrete regions with a similar trend observed between drug (Figure 3) vs drug encapsulated lipid (Figure 4). Although, there are variations in wavelength number.

Would the more experienced among you have any comments and/or advice regarding this?

Thank you all for your help.