Reversed-phase ion-pair chromatography of oligodeoxyribonucleotides

The separation of large oligodeoxyribonucleotides, synthesized chemically and subsequently deblocked, was carried out by reversed-phase ion-pair chromatography (RP-IPC) with a linear gradient of acetonitrile concentration. It was found that tetrabutylammonium phosphate is suitable as an ion-pairing reagent and produces a linear relationship between the base numbers of the samples and their elution volumes. It was also verified that various factors effective in reversed-phase chromatography, such as temperature, end-capping of the columns, differences in the type of C18 alkylating reagents and in the base silica, and the pore size of the base silica have little effect on the resulting separation by RP-IPC.