In the chromatogram of this application one can observe a distinct grouping of the acids into singly charged and doubly charged ions typically make separations of ions of different charges rather straightforward. In contrast can the task to achieve separation between ions of the same charge be a much more challenging task which may result in co-elution of compounds. The difference in retention of the carboxylic acids having the same charge illustrates how chemical characteristics such as hydrophilicity, hydrophobicity and molecular structure influence retention.
