Analysis of alkane, alkene, aromatic and oxygenated groups in petrochemical mixtures by supercritical fluid chromatography on silica gel

Pre-separation into chemical class by chromatographic methods is a powerful aid to analysis by capillary gas chromatography and provides valuable info rmation in itself, since fuel properties are to a large extent dependent on the chemical group composition. Normal-phase supercritical fluid chromatog raphy on silica gel has become the established method for the separation of the aromatic and aliphatic groups in petrochemical samples. This method wa s extended to include the analysis of alkane, alkene and oxygenate groups i n gasoline range samples without significantly increasing the complexity of instrumentation. A systematic study of chromatographic parameters demonstr ated that alkane-alkene group selectivity increases at high pressures. A fl ow splitter was built into the system and a new restrictor interface was de signed to allow off-line transfer of separated groups to the GC or CC-MS fo r detailed characterization. (C) 1999 Elsevier Science BN. All rights reser ved.