The chromatographic behavior of a number of low boiling eluents has been compared in supercritical fluid chromatography ( S F C ) with packed columns. Unmodified silica gel has been used as the stationary phase and a test mixture of polycyclic aromatic hydrocarbons ( P A H I S ) as the substrate. Carbon dioxide, nitrous oxide, trifluoromethane, chlorotrifluoromethane, n-pentane, n-butane, 1-butane, propane, ethane, dicthylether, and dimcthylethtr have beon investigated as mobile phases. LEYENDECKER ET ALOf the mobile phast -C O L , N 2 0 , C 2 t f 6 , C H F 3 , and C C I F J , which a l l possess low c'r? ticdl ternp(.ratur

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A comparative study on the chromatographic properties of the alkanes n-pentane, n-butane, iso-butane, and propane in the liquid and the supercritical state has been performed using silica gel as the stationary phase and four condensed aromatic compounds as the substrates. At supercritical conditions, chromatographic parameters can be influenced by temperature and pressure to a greater extent than at liquid conditions. Both the capacity ratios and overall resolutions reach maximum values at supercritical state. The maxima become more pronounced with decreasing critical temperature of the mobile phase. The possibilities for optimizing a chromatographic analysis with supercritical eluents are considerable.

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