Dmitry, You can use SARA (Saturates, Aromatics, Resins, Asphaltenes) method separation by Liquid chromatography using different solvents for preparation  samples, and further analysis by MS and NMR and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS).

If I remember correctly, I have come across a few publications where High / Ultra-high Resolution Mass Spectroscopic Technique was used for the determination of molecular mass of various components present in bitumen. 

If various components can be separated, as suggested by Dugic, ahead of the actual analysis, the problem will definitely be quite a bit simplified.