Retention behaviour of an homologous series of oligodeoxythymidilic acids using reversed-phase ion-pair chromatography

The retention behaviour of an homologous series of phosphorylated oligodeoxythymidylic acid (pd(T)(5-18)) oligonucleotides was studied using reversed-phase ion-pair chromatography with isocratic elution conditions. The effects of temperature, pH, eluent ionic strength, percentage organic modifier, concentration and alkyl chain length of the ion-pairing reagent were investigated. The retention behaviour was generally explicable by current theoretical models of ion-pair chromatography However, the marked effect of mobile phase pH on the retention of the oligonucleotides was unexpected, and this was ascribed to the presence of ionisable residual silanols on the surface of the reversed-phase packing material.