Shape-Selective Separation of Model Analytes in Normal-Phase Liquid Chromatography: A Combined...

Area of Science:

• Analytical Chemistry
• Separation Science
• Physical Chemistry

Background:

• Chromatographic separation typically relies on chemical interactions.
• Molecular shape anisotropy is often overlooked in separation strategies.
• Understanding analyte-surface interactions is crucial for optimizing separations.

Purpose of the Study:

• To demonstrate shape-based liquid chromatography separation for molecules with similar chemical properties.
• To investigate the retention behavior of spherical buckminsterfullerene C60 and disk-shaped coronene.
• To elucidate the role of mobile phase composition and solvent layering in separation.

Main Methods:

• Combined experimental (High-Performance Liquid Chromatography) and theoretical (molecular simulations, two-state model) approaches.
• Analysis of retention behavior using varying toluene and n-hexane mobile phase compositions.
• Determination of Henry coefficients to understand adsorption thermodynamics.

Main Results:

• Effective separation of C60 and coronene was achieved based on their shape differences.
• Increased n-hexane content in the mobile phase enhanced analyte separability, with coronene showing stronger retention.
• Molecular simulations revealed structured toluene layering at the stationary phase, influencing differential analyte-wall interactions.
• The second solvent layer was identified as critical for adsorption and separation.

Conclusions:

• Molecular shape anisotropy is a significant factor in chromatographic retention.
• Mobile phase composition and solvent structure at the interface dictate separation efficiency.
• Findings suggest new strategies for shape-selective separations of molecules and nanoparticles.