Analysis of coal tar polycyclic aromatic hydrocarbon LC-fractions by capillary SFC on a liquid crystalline stationary phase

Abstract

Supercritical fluid chromatography (SFC) on a capillary column coated with a smectic mesomorphic crystalline phase is shown to exhibit a typical turnover effect (retention versus column temperature) for polycyclic aromatic hydrocarbons (PAHs) at lower temperatures than are found on a methylpolysiloxane phase. Liquid chromatography is used to separate various fractions from a coal tar, which are analyzed by high resolution capillary SFC. Different density and temperature programs were investigated to optimize the separations. Simultaneous density and temperature programs gave the best results, and this is thought to be due to increased solute diffusion coefficients which yield highly efficient separations for the high molecular weight polycyclic aromatic hydrocarbons. The separation mechanism is based on the shape of the liquid crystalline phase, solubility, volatility, and molecular geometry of the PAHs.