beta-Cyclodextrin as a stationary phase for the group separation of polycyclic aromatic compounds in normal-phase liquid chromatography.

The separation of highly alkylated polycyclic aromatic compounds according to the size of their aromatic system is investigated using the polycyclic aromatic sulfur heterocycles in vacuum gas oil. A large number of reference compounds containing several parent ring systems and different alkylation patterns were first investigated to characterize the retention of polycyclic aromatic compounds likely to occur in high-boiling petroleum samples. A beta-cyclodextrin phase, Merck ChiraDex, was found to be more suitable than chemically bonded aminopropanosilane and tetrachlorophthalimide in normal-phase HPLC with respect to a combination of selectivity towards the number of aromatic double bonds and degree of influence of the alkyl groups of the aromatic compounds. Finally the preseparated polycyclic aromatic sulfur heterocycles from a vacuum gas oil were fractionated according to the number of condensed aromatic rings on the ChiraDex phase and were characterized by Fourier transform ion cyclotron resonance mass spectrometry.