On-line multidimensional chromatography using supercritical carbon dioxide

A two-dimensional chromatographic separation is described which makes use of the unusual properties of supercritical carbon dioxide mobile phase. This solvent has the property of giving a separation of polycyclic aromatic hydrocarbons (PAH) on amine-bonded columns similar to that given by usual normal-phase solvents, and on octadecylsilane-bonded columns similar to that given by usual reversed-phase solvents. Packed columns were used, arranged so that they could be switched in or out of the solvent flow. Polycyclic aromatic hydrocarbon mixtures isolated from coal tar were fractionated according to number of aromatic carbon atoms on an amine-bonded column, and these fractions were trapped on an octadecysilane-bonded column. They were subsequently eluted according to the polarity of the individual compounds. Separations from fractions containing 16 and 18 aromatic carbon atoms are shown.