Key Words:Capillary GC Off-line LC preseparation Trace analysis Aromatic compounds in an n-alkane matrix SummaryThe possibilities and difficulties of trace analysis of highly complex organic mixtures has been demonstrated by the analysis of traces of numerous aromatic substances in an n-alkane matrix with a boiling point range of 151-270°C. Single column high resolution capillary gas chromatography (under optimized conditions) was performed after an off-line LC preseparation step which had been evaluated using a model mixture.Gas chromatographic quantitation of the 191 aromatic compounds identified was performed with an internal standard; following splitless injection and separation on a polydimethylsiloxane column under temperature-programmed conditions the compounds were detected by flame ionization. The response factors of aromatic hydrocarbons at trace levels were verified and the precision and reproducibility both of the GC determination and the overall analysis, including preseparation, were studied.Percentage by weight of individual aromatic compounds (mainly alkylbenzenes, indanes, naphthalenes, and acenaphthenes) was in the range lo9 to