dear researcher

interpretation of mass spectrometer data is very complected if you want to use your own knowledge about fragmentation, it is easy to use MS library and to compare between your spectrum and the suggested one, however the highest similarity is more expected to be true. in fact that the most updated library does not contain all compounds in nature so its necessary if you isolate a compound and you need to be sure about it structure you need to subject it for more chemical analysis using (eg. H NMR, X ray crystallography).

If you have the same spectra and the same retention times, it usually is the same compound. (Generally accepted proof) however if there is more doubt then you might want to isolate and do NMR experiments.