The polars are usually aromatic in nature and consist of compounds that may contain nitrogen, sulfur and oxygen as heteroatoms.
Asphaltenes are highly condensed aromatic structures.
Conventional TLC with silica and alumina adsorbents provides separation of components from crude
oils based on their polarity.
TLC with Same ionization detection (TLC-FID) has been applied for the determination of hydrocarbon types.
SEC has been particularly useful for the characterization of heavy crude oil fractions.