Effect of Mobile Phase pH and Counterion Concentration on Retention and Selectivity for a Diol Column in Hydrophilic Interaction Liquid Chromatography

This work focuses on the effects of the mobile phase pH and the counterion concentration in buffer solution on retention in hydrophilic interaction liquid chromatography (HILIC) mode. Analytes with various acid-base properties and a silica-based Diol stationary phase were used. Retention and separation selectivity changes with ionization of the analytes and the adsorbent’s groups were discussed. It was demonstrated that the Diol phase behaved as a cation exchanger at pH 5.76 because of its residual dissociated silanols, while the phase provided almost no charge at lower pH (2.85). Separation efficiency and asymmetry factors for ionized compounds were also affected by the changes of mobile phase pH and counterion concentration. Separation conditions for the mixture of analytes of various acid-base properties were established.