Towards a microchip-based chromatographic platform. Part 2: sol-gel phases modified with polyelectrolyte multilayers...

Area of Science:

• Analytical Chemistry
• Materials Science
• Separation Science

Background:

• Sol-gel chemistry enables continuous silica networks for chromatographic applications.
• Polyelectrolyte multilayers (PEMs) can impart tunable surface properties.
• Capillary electrochromatography (CEC) is a powerful separation technique.

Purpose of the Study:

• To evaluate the use of PEMs for chromatographic functionality on sol-gel derived silica networks.
• To investigate how PEM properties influence chromatographic performance in CEC.
• To explore methods for controlling electroosmotic flow (EOF) and separation capacity.

Main Methods:

• Constructed PEMs on silica networks by sequential deposition of oppositely charged polyelectrolytes.
• Utilized CEC to analyze the chromatographic behavior of modified silica columns.
• Varied the composition (e.g., poly(diallyldimethylammonium chloride), dextran sulfate, poly(styrene sulfonate)) and thickness of the PEMs.

Main Results:

• Changing the exposed polyelectrolyte altered EOF direction and chromatographic capacity.
• Switching from dextran sulfate to poly(styrene sulfonate) significantly modified EOF and peptide migration, increasing both reversed-phase and ion-exchange capacities.
• Increasing PEM thickness enhanced anion retention by 70-80% without affecting EOF, indicating analyte penetration and interaction with internal charges.

Conclusions:

• PEMs provide a versatile platform for tailoring chromatographic surfaces on sol-gel silica.
• Surface modification through PEMs allows for independent control over EOF and separation mechanisms (reversed-phase, ion-exchange).
• PEM thickness is a key parameter for optimizing analyte retention, particularly for ion-exchange interactions.