Retention Models on Core-Shell Columns.

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Core-shell columns in HPLC provide high efficiency due to a thin, active outer layer.
• Retention modeling in mixed aqueous-organic mobile phases is crucial for method development.

Purpose of the Study:

• To evaluate three retention models (linear solvent strength, Snyder-Soczewiński two-parameter, and a three-parameter model) for core-shell columns.
• To compare the predictive accuracy of these models across different bonded phases (C18, phenyl-hexyl, biphenyl).

Main Methods:

• Investigated mobile phase effects on retention using mixed aqueous-organic solvents.
• Formulated a retention equation based on solute retention factors in pure solvents and mobile phase composition.
• Defined and utilized thermodynamic retention factors, excluding the inert core volume.

Main Results:

• The three-parameter model showed improved accuracy by accounting for potential minor retention in pure weak solvents, unlike two-parameter models.
• Phenyl-hexyl and biphenyl core-shell columns exhibited lower prediction errors for alkylbenzenes, phenolic acids, and flavonoids compared to C18 columns.
• Consistent use of thermodynamic or conventional retention factors yielded correct predictions for mobile phase effects.

Conclusions:

• A three-parameter retention model offers superior prediction of analyte retention on core-shell columns in mixed mobile phases.
• Phenyl-hexyl and biphenyl phases are advantageous for certain compound classes, showing better model agreement.
• Understanding retention mechanisms and proper factor definition is key for accurate HPLC method optimization.