A survey of polar stationary phases for hydrophilic interaction chromatography and recent progress in understanding retention and selectivity

Abstract

Various polar stationary phases are available for hydrophilic interaction chromatography (HILIC) and help drive continuous applications in biomedical, environmental, and pharmaceutical areas in the past decade. Although the stationary phases for HILIC have been reviewed previously, it is an appropriate time to take another look at the progresses made during the past 5 years. The current review provides an overview of the polar stationary phases commercially available for HILIC applications in an effort to assist scientists in selecting suitable columns. New types of stationary phases that were published in literature in the past 5 years are summarized and discussed. The trend in stationary phase research and development is also highlighted. Of particular interest is the experimental evidence for direct interactions of polar analytes with the ligands of the stationary phases under HILIC conditions. In addition, two different approaches have been developed to delineate the relative significance of the partitioning and adsorption mechanisms in HILIC, representing an important advancement in our understanding of the retention mechanisms in HILIC.

Multi-2D LC × LC as a Novel and Powerful Implement for the Maximum Separation of Complex Samples

“…At this point, it is important to remark the difficulty of carrying out good 2 D separations using HILIC. It is proposed that the main retention factor of the analytes in HILIC results from the partition between a thin aqueous layer adsorbed around the particles and the highly organic mobile phase, besides the direct interaction of the analytes with the stationary phase ligands . The formation of this aqueous layer is very important for retention and reproducibility, and this is one of the most critical points in HILIC.…”

“…It is proposed that the main retention factor of the analytes in HILIC results from the partition between a thin aqueous layer adsorbed around the particles and the highly organic mobile phase, besides the direct interaction of the analytes with the stationary phase ligands. 14 The formation of this aqueous layer is very important for retention and reproducibility, and this is one of the most critical points in HILIC. To achieve a full reequilibration of the HILIC phases, very long equilibration times (tens of minutes or hours) are required before the next analysis when a gradient elution analysis is done.…”

Hydrophilic Partitioning or Surface Adsorption? A Quantitative Assessment of Retention Mechanisms for Hydrophilic Interaction Chromatography (HILIC)

“…Hydrophilic interaction chromatography (HILIC) has established itself as a unique mode of chromatographic separation over the past three decades. Often considered complementary to reversed-phase liquid chromatography (RPLC), HILIC provides stronger retention to small polar compounds on polar stationary phases using a mobile phase of water and organic solvents (e.g., acetonitrile) [ 1 , 2 , 3 , 4 , 5 , 6 ]. In his seminal paper published in 1990, Alpert postulated the retention mechanisms for HILIC.…”