Use of Pyrocarbon Sorbents for Trace Enrichment of Polar Compounds from Aqueous Samples with On-line HPLC Analysis

Abstract

The advantages of pyrocarbon as a sorbent for the trace enrichment of polar aromatic compounds from aqueous solutions, compared to apolar chemically bonded silica-based sorbents, is demonstrated. The differences in sorption properties are explained in terms of differences in retention mechanism. The capacity factors of the solutes on pyrocarbon are related to their free energy of adsorption onto the surface. Contrary to the situation with chemically bonded phases, interaction with the stationary phase plays a major role. Capacity factors in the system of pyrocarbon/pure water (and thus, enrichment factors during trace enrichment) can easily be predicted on the basis of a limited number of chromatographic retention data. Pyrocarbon-packed precolumns can be coupled to both pyrocarbon- and silica-packed analytical columns; i.e., final separation is possible in both reversed- and normal-phase modes. The method has been applied to the determination of nitrobenzene in surface water, using both UV and electrochemical detection.