Despite the significant efforts that have been made to systematically evaluate and optimize mobile phase components in ion-pair chromatography of oligonucleotides, one of the most influential parameters has never been seriously addressed. This is particularly noteworthy since ion-pair chromatography relies on the ability to effectively control pH in order to maintain efficient ionic interactions during separations. There is growing evidence that many of the most significant challenges in LC–MS of oligonucleotides are greatly influenced by the pH of the mobile phase. Among these challenges the two that appear to be the most influenced by pH are mobile phase stability (also known as aging) and nonspecific adsorption.
Learning Objectives:
Define how mobile phase stability (also known as aging) and nonspecific adsorption are influenced by mobile phase pH.
Understand how nonspecific adsorption impacts impurity analysis of oligonucleotides.
Identify optimal mobile phase pH for ion-pair LC-MS analysis of oligonucleotides.
