On-line liquid distribution chromatographic/spectrofluorometric determination of PAH distribution in coal-derived products

Abstract

On-line HPLC/Spectrofluorometric techniques have been applied to the determination of polycyclic aromatic hydrocarbons (PAHs) in coal-derived products. The PAHs were isolated by preparative silica gel columns with a hexane mobile phase, and fractionated into five samples based on the number of condensed rings. Each fraction was separated by reverse phase HPLC with an acetonitrile/water mobile phase. Compounds were detected by means of on-line fluorescence detection. Naphthalene, pyrene, fluoranthene, benzo(a)anthracene and benzo(a)pyrene were verified by comparing the excitation and emission spectra obtained by a stop-flow technique with those of PAH standards.

A Picramido bonded phase packing was prepared by the reaction of picryl chloride and amino bonded phase silica gel, forming a charge-transfer active phase. The retention mechanism of aromatic hydrocarbons on the picramido bonded phase column was studied in three ways: electronic effects (Hammett cr function); temperature effects on heats of adsorption and solvent effects on capacity factors.

Chromatographic properties of the picramido bonded phase column were compared to those of silica gel and amino bonded phase columns.

An on-line LC/LC column switching system was developed for PAH analysis of solvent refined coal (SRC). It utilized a guard column, an amino bonded phase, and a picramido bonded phase column. The guard column prevented the highly polar materials from entering the analytical columns; the amino bonded phase column separated PAH materials into groups based on an adsorption mechanism; the picramido bonded phase column separated PAHs based on charge-transfer mechanism, and provided better resolution.