Separation of carboxylates by hydrophilic interaction liquid chromatography on titania

Hydrophilic interaction liquid chromatography (HILIC) can be performed on titania. To better understand the retention mechanisms on titania, a series of model carboxylates were used. Increasing acetonitrile above 60% dramatically increased the retention and efficiency for carboxylates. The effect of buffer type, buffer concentration, buffer pH and column temperature were also studied. Multiple retention mechanisms are operative on titania, and whether electrostatic repulsion, ligand exchange or HILIC dominates retention and separation depends on the eluent conditions. Guidelines for separations on titania are: (1) higher %ACN most improves retention and efficiency; (2) higher salt concentration increases retention; (3) elution strength is in the order acetate<