Hydrophilic interaction chromatography of polar and ionizable compounds by UHPLC

In recent years, the popularity of hydrophilic interaction chromatography (HILIC) in the analysis of small polar and ionizable molecules increased substantially. A large number of new stationary phases with sub-2-µm and superficially porous particles were developed and used in various applications, including pharmaceuticals, metabolites, biomarkers, amino acids and peptides. Applications of HILIC in ultra-high performance liquid chromatography (UHPLC) mode constitute only about 10% of all current HILIC applications. This review presents an overview of UHPLC in HILIC mode, including the importance of the final sample diluent, a discussion on available stationary phases and approaches to detection, and a comparison of performance with other chromatographic modes.