Comparison of the Fitting Performance of Retention Models and Elution Strength Behaviour in Hydrophilic-Interaction and Reversed-Phase Liquid Chromatography

Hydrophilic interaction liquid chromatography (HILIC) effectively separates polar to highly polar solutes using eluents similar to those in reversed-phase liquid chromatography (RPLC) and a polar stationary phase that adsorbs water on its surface. HILIC interactions are known to be more complex than those in RPLC, making accurate modelling for predicting retention and understanding retention mechanisms intricate. This study examines the predictive performance of several retention models across seven HILIC columns (including underivatised silica and silica with diol, amino, and sulfobetaine functional groups, as well as three recently manufactured columns with neutral, anionic, and cationic characteristics) using uracil and six polar nucleosides (adenosine, cytidine, guanosine, thymidine, uridine, and xanthosine) as probes. Results from HILIC are compared to those from polar sulphonamides and diuretics analysed with two C18 columns (Chromolith Speed ROD and Zorbax Eclipse XDB). The study finds that eight retention models, which consider partitioning or both partitioning and adsorption, provide similar accuracy for predictions in both HILIC and RPLC. Furthermore, variations in elution strength with changing mobile phase composition reveal similarities and differences between the behaviours of RPLC and HILIC columns. These behaviours were also analysed by fitting retention data to a model that describes changes in elution strength based on modifier concentration.