GAS-CHROMATOGRAPHIC ANALYSIS OF HIGH-MOLECULAR-MASS POLYCYCLIC AROMATIC-HYDROCARBONS .2. POLYCYCLIC AROMATIC-HYDROCARBONS WITH RELATIVE MOLECULAR MASSES EXCEEDING 328

Three columns were used for the gas chromatographic analysis of polycyclic aromatic hydrocarbons (PAHs) with relative molecular masses (M(r)) up to 450. Two of the columns were commercially available, coated with a 50% methyltrifluoropropyl-substituted polysiloxane and a 5% diphenyl-substituted methylpolysiloxane. The third column was laboratory made, coated with a biphenyl-substituted silarylene-siloxane copolymer. All three columns were utilized for the analysis of high-M(r) PAHs as regards both thermal stability of the stationary phases. i.e.. low bleeding rate, and chromatographic efficiency. The column coated with a trifluoropropyl-substituted stationary phase showed, however, a low separation efficiency, possibly owing to low solute stationary phase compatibility. The biphenyl-substituted stationary phase, on the other hand, showed a very high separation efficiency, but the retention of the PAHs was significantly higher on this column compared with the other two, leading to the demand for higher oven temperatures. Different retention mechanisms were observed on these columns, as shown by differences in the retention indices of the PAHs measured in a system using PAHs as retention index markers. A comparatively faster elution of non-planar PAHs was observed on the columns coated with the trifluoropropyl-substituted stationary phase and the biphenyl-substituted stationary phase compared with the column coated with the 5% diphenyl-substituted polymer. The usefulness of the columns for separations of high-M(r) PAHs is demonstrated by gas chromatograms of carbon black extracts and a coal tar extract standard reference material.