Column selectivity in reversed-phase liquid chromatography. VI. Columns with embedded or end-capping polar groups

Area of Science:

• Analytical Chemistry
• Chromatography

Background:

• Reversed-phase liquid chromatography (RP-LC) is a key separation technique.
• Understanding column selectivity is crucial for method development.
• Previous models exist for non-EPG columns.

Purpose of the Study:

• To evaluate the selectivity of 21 additional RP-LC columns with embedded or end-capping polar groups (EPGs).
• To compare the selectivity of EPG columns with non-EPG columns.
• To expand a database of RP-LC column selectivity.

Main Methods:

• Application of a previous RP-LC column selectivity model to 21 new EPG columns.
• Comparison of retention behavior between EPG and non-EPG columns.
• Data compilation to create an expanded column selectivity database.

Main Results:

• Embedded-polar-group (EPG) columns exhibit significantly different selectivity compared to non-EPG, type-B columns.
• EPG columns preferentially retain hydrogen-bond donors and show decreased retention for hydrogen-bond acceptors or ionized bases.
• Columns with polar end-capping more closely resemble non-EPG columns than embedded polar group columns.
• EPG columns are generally less hydrophobic (more polar) than non-EPG columns.

Conclusions:

• Embedded polar groups significantly alter RP-LC column selectivity, particularly for hydrogen-bonding interactions.
• Polar end-capping has a less pronounced effect on selectivity compared to embedded polar groups.
• An expanded database of 154 columns allows for selectivity comparisons, though EPG column comparisons are approximate.