Zone formation in ion-pair RPLC II. System peak retention and effects of desorption of organic ions on established column equilibria

Summary

Desorption of some organic ions from μBondapak Phenyl was studied. The half height of the desorption curve was used to describe the retention volumes. When the column was equilibrated with two organic ions with opposite charge and one of them was desorbed, the other ion was also partially desorbed and observed as a positive zone. The retention volumes of systems peaks created by disturbing the equilibria in the column, equilibrated with at least one organic ion, were studied. The net retention volumes of the break-through curve, obtained from the adsorption of organic ions, system peaks and desorption curves were compared. At low concentrations of the adsorbable ion in the eluent all three types of retention volumes were equal. Negative zones, obtained when introducing an organic ion into a column equilibrated with an organic ion of the opposite charge, could be used to perform step gradient elution of ionic compounds. By using suitable conditions narrow peaks were obtained.