Sulfonic Functionalized Polydopamine Coatings with pH-Independent Surface Charge for Optimizing Capillary...

Area of Science:

• Analytical Chemistry
• Separation Science
• Materials Science

Background:

• Achieving pH-independent electroosmotic flow (EOF) is crucial for reproducible capillary electrophoresis (CE) separations.
• Existing methods often struggle to maintain stable EOF across a wide pH range, limiting analytical performance.
• Controlling EOF magnitude is essential for optimizing separation efficiency and analysis time.

Purpose of the Study:

• To develop a novel capillary modification method for pH-independent and reproducible cathodic EOF in CE.
• To investigate the use of sulfonated periodate-induced polydopamine (SPD) coatings for capillary inner surface modification.
• To evaluate the performance of SPD-coated capillaries in enhancing CE separation efficiency and reproducibility.

Main Methods:

• Fabrication of SPD-coated capillaries via post-sulfonation of periodate-induced polydopamine (PDA-SP) coatings.
• Characterization of SPD coatings using various analytical techniques to confirm immobilization and sulfonation.
• Evaluation of EOF mobility, pH-dependence, and silanol group masking capabilities of the modified capillaries.

Main Results:

• Successful immobilization of SPD coatings with substantial sulfonic acid group grafting confirmed.
• SPD-coated capillaries effectively masked silanol groups and exhibited robust, high-strength cathodic EOF, largely independent of pH.
• Optimized SPD columns demonstrated high-efficiency separations of aromatic acids, nucleosides, and rapid chiral analysis of racemic drugs.

Conclusions:

• The developed SPD coating method provides a robust approach to achieving stable, pH-independent EOF in CE.
• SPD-coated capillaries significantly enhance separation performance, reproducibility, and analytical efficiency.
• These modified capillaries offer a long lifetime and excellent repeatability, making them suitable for routine analytical applications.