Mahsa Ostadgholami

The classic qualitative determination of methyl salicylate in a gel can be done by taking the IR spectra of the mixture and pure methyl salicylate. The characteristic absorption bands of the ester group will indicate its presence. If you have a Raman spectrometer, that will help too.

if there are only traces of other aromatic compounds UV-Spectrometry should be very sensitive,

what is the basis of the gel.

The best method always depends on the other compounds present.