“…Each of these fractions has a particular solubility in paraffinic (such as heptane), aromatic (such as toluene), and polar (such as dichloromethane) solvents. Depending on the proportions of these fractions as well as its tendency to precipitate organic scales, it is possible to classify a crude oil as stable or unstable. , Regardless of the oil, asphaltenes present the greatest challenge due to their influence on the general behavior of crude oil, such as its emulsifying tendency, the precipitation of organic scales, and its viscosity. , Asphaltenes are difficult to characterize because they are defined in terms of their solubility and not their composition. For example, different “asphaltenes” can be obtained from the same crude oil simply by changing the precipitant used. , Several techniques have been employed in asphaltene characterization, such as infrared spectroscopy (IR), − matrix-assisted laser desorption/ionization mass spectrometry (MALDI/TOF), ultrasmall-angle X-ray scattering, X-ray diffraction (XRD), nuclear magnetic resonance (NMR), Fourier transform-ion cyclotron resonance-mass spectrometry (FT-ICR-MS), , and atomic force microscopy (AFM) .…”