Class separation of polycyclic aromatic hydrocarbons, nitrogen heterocycles and hydroxyl aromatics by liquid chromatography

Abstract

High-performance liquid chromatography has been used to separate polycyclic aromatic hydrocarbons, nitrogen heterocycles, and hydroxyl aromatics which are known or suspected to be present in solvent refined coal samples. The separation of these model compounds by compound-class was accomplished with normal-phase μPorasil and Nucleosil NO 2 columns. n-Heptane, n-heptane—chloroform, carbon tetrachloride—chloroform and carbon tetrachloride—dimethyl sulfoxide mobile phases were used to separate the model compounds. Polar standards were chromatographed with mobile phases of several solvent strengths to observe the different migration behavior of the functional classes. It was found that the μPorasil column utilizing a carbon tetrachloride—chloroform mobile phase offered the best separation of polycyclic aromatic hydrocarbons and nitrogen heterocycles. μPorasil also yielded superior separation of nitrogen heterocycles from hydroxyl aromatics when a carbon tetrachloride—dimethyl sulfoxide eluent was employed.