As an alternative high performance liquid chromatography technology, hydrophilic interaction liquid chromatography (HILIC) plays an important role in the separation of highly polar and ionic compounds such as amino acids, carbohydrates, peptides and so on. The development of HILIC stationary phases, which are considered as the core of chromatographic technology, is of great importance for the improvement of chromatographic separation selectivity and efficiency, influencing the application and generalization of HILIC. To date, a great variety of commercial and academic HILIC materials with abundant functional groups have been presented. According to the functional groups of chromatographic materials, the development of silica-based HILIC stationary phases including unmodified silica, amino-based, cyano-based, diol-based, amide-based, poly(succinimide)-based, saccharides-based and zwitterion-based stationary phases are reviewed in the present article. Meanwhile, the typical applications of HILIC stationary phases in polar drugs separation, bioanalysis, proteomics, metabolomics, etc. are included. With increasing diversity of HILIC materials, the selection of appropriate HILIC stationary phase for the resolution of complex compounds becomes difficult. The development of systematic test samples and methods to access the separation selectivity is of great value for understanding the interaction mechanism of HILIC stationary phases. Thus, the investigation involving test samples to evaluate separation efficiencies and selectivities in HILIC is also reviewed.

Contents
1 Introduction
2 Development and application of hydrophilic interaction chromatographic materials
2.1 Unmodified silica
2.2 Amino-based stationary phase
2.3 Cyano- and diol-based stationary phase
2.4 Amide-based stationary phase
2.5 Poly(succinimide)-based stationary phase
2.6 Saccharides-based stationary phase
2.7 Zwitterion-based stationary phase
3 Chromatographic evaluation of hydrophilic interaction chromatographic materials
4 Conclusion and outlook