High-Pressure Gas Chromatography and Chromatography with Supercritical Fluids. III. Fluid-Liquid Chromatography

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Abstract
High-boiling substances can be separated by partition chromatography, using n-pentane and isopropanol under supercritical conditions as mobile carriers. At moderate temperatures (200–250°C) the volatility of heavy substances may be enhanced by a factor of as much as 104 by increasing the pressure from atmospheric to about 50 kg/cm2. This enables the analysis of compounds which are too heavy for ordinary gas chromatography. As predicted before on the basis of gas-chromatographic studies at elevated pressures, the use of supercritical mobile fluids in combination with liquid stationary phases results in an attractive separation procedure. This technique is rapid and has a high degree of flexibility. Separations according to boiling point as well as molecular type are possible. The main features of the new chromatographic technique, for which the designation “fluid-liquid chromatography” (FLC) is proposed, are illustrated by means of several examples.