β-cyclodextrin-anchored C18 brush stationary phases with enhanced shape selectivity for reversed-phase HPLC

Area of Science:

• Chromatography
• Materials Science
• Analytical Chemistry

Background:

• Reversed-phase chromatography (RPC) faces challenges with shape selectivity and stability in high-aqueous mobile phases.
• Existing C18 stationary phases often exhibit hydrophobic collapse and limited molecular recognition capabilities.

Purpose of the Study:

• To develop novel β-cyclodextrin-anchored stationary phases with enhanced shape selectivity and high-aqueous stability.
• To investigate the structure-retention relationships and separation mechanisms of these new materials.

Main Methods:

• Synthesized two β-cyclodextrin-anchored reversed-phase stationary phases (β-CD-COOC18 and β-CD-NHCOOC18) using a rigid anchor-flexible chain strategy.
• Immobilized stationary phases onto silica via thiol-ene click chemistry.
• Evaluated shape selectivity using Tanaka tests and separation performance with isomeric systems and polar compounds under various aqueous conditions.

Main Results:

• The developed β-CD-C18 phases demonstrated significantly improved shape selectivity (α = 2.37) compared to a commercial C18 column (α = 1.41).
• These phases exhibited excellent stability and performance in 100% aqueous mobile phases, enabling separation of highly polar nucleosides and bases.
• The unique architecture facilitated a synergistic multiple-interaction mechanism involving steric recognition and secondary interactions.

Conclusions:

• The rigid macrocyclic scaffold strategy effectively integrates specific shape recognition with broad reversed-phase applicability.
• The β-cyclodextrin-anchored stationary phases offer a promising solution for separating challenging isomeric and polar compounds under extreme aqueous conditions.