Effect of Packed Materials of Column on the Retention Mechanism in Reversed Phase Liquid Chromatography

Abstract

Reversed phase liquid chromatography (RPLC), the most widely used mode in highperformance liquid chromatography, commonly uses silica gel as a support material for columns, on which octadecyl chain is chemically grafted. In RPLC, the solvophobic theory has been used to explain the retention mechanisms of hydrophobic or partly hydrop hobic solutes on RPLC columns, but we have still some problems that can not be explained by the theory. An example is the fact that nucleosides having a hydrophilic ribose ring show more preferential retention on silica-based RPLC columns (ODS columns) than their corresponding bases which are highly hydrophobic. Two possible factors for this unusual retention are the unusual hydrophobic interaction between solutes and octadecyl chains and the specific interaction of solutes with silica gel. In order to elucidate this fact, vinyl alcohol copolymer gel, whose retention mechanism for such solutes has been explained by the solvophobic theory, was taken as a support material and the retention of nucleosides and their bases were investigated on a column packed with octadecyl chain-grafted vinyl alcohol copolymer gel. It was revealed that the retention of all samples on the packing was well explained by the solvophobic theory and such samples were adsorbed on an ODS silicagel with unusual retention behavior. The extraordinary long retention of adenosine 3', 5'-cyclic phosphate on ODS silica columns was determined to be due to the similar interaction between silica gel and the solutes.