Chapter 2 - Advances in Hydrophilic Interaction Liquid Chromatography

Abstract

Hydrophilic interaction liquid chromatography (HILIC) is suitable for separations of strongly or moderately polar samples on polar columns in aqueous–organic mixed mobile phases with high concentrations of aprotic solvents. The samples in HILIC are distributed between the bulk mobile phase and the stationary phase, which includes the solid sorbent itself and water preferentially adsorbed by the solid phase. As the stationary phase is more polar than the bulk mobile phase, comprising a relatively low concentration of water in an organic solvent (usually aprotic such as acetonitrile), the separation system is a normal-phase one. The amount of the adsorbed water strongly depends on the type of polar column and may be used to distinguish between “conventional HILIC” and “aqueous normal-phase chromatography.” Many types of columns can be used in HILIC based on silica gel, chemically bonded phases, organic polymers, or metal oxide supports, including particulate, surface porous (core shell), or monolithic columns. This chapter presents a survey of the suitable polar columns for HILIC separations, including recent additions to the family. Some columns containing hydrocarbon moieties show a dual HILIC–reversed-phase (RP) mechanism, depending on the mobile phase composition. Columns with ionic groups may show combined HILIC–ion exchange or HILIC–ion repulsion interactions. The role of mobile phase is also addressed. Some application examples are presented.