Novel zwitterionic polyphosphorylcholine monolithic column for hydrophilic interaction chromatography

Area of Science:

• Chromatography
• Materials Science
• Polymer Chemistry

Background:

• Chromatographic methods are essential for separating complex mixtures.
• Developing novel stationary phases with unique separation mechanisms is crucial for advancing analytical chemistry.
• Zwitterionic materials offer potential for versatile chromatographic applications due to their dual charge characteristics.

Purpose of the Study:

• To synthesize and characterize a novel porous zwitterionic monolith for chromatographic separations.
• To investigate the separation mechanisms and performance of the zwitterionic monolith for polar and charged analytes.
• To evaluate the monolith's stability and selectivity, particularly for small peptides.

Main Methods:

• Thermal co-polymerization of 2-methacryloyloxyethyl phosphorylcholine (MPC) and ethylene glycol dimethacrylate (EDMA) in capillaries.
• Characterization using mercury intrusion porosimetry, scanning electron microscopy (SEM), micro-HPLC, elemental analysis, and zeta-potential analysis.
• Evaluation of chromatographic performance with polar analytes, small peptides, and alkylphenones under varying mobile phase conditions.

Main Results:

• A stable porous zwitterionic monolith (poly(MPC-co-EDMA)) was successfully prepared without swelling or shrinking in different solvents.
• The monolith exhibited hydrophilic interaction liquid chromatography (HILIC) behavior at high organic solvent content (>60% acetonitrile).
• Weak electrostatic interactions were observed for charged analytes, influenced by mobile phase pH and salt concentration.
• Excellent selectivity was achieved for polar analytes, especially small peptides, and baseline separation of alkylphenones via reversed-phase mechanism at low organic content.

Conclusions:

• The poly(MPC-co-EDMA) monolith serves as a versatile stationary phase capable of dual separation mechanisms (HILIC and reversed-phase).
• The zwitterionic nature and biocompatibility of the phosphorylcholine (PC) functionality contribute to its high selectivity for polar compounds like peptides.
• This novel monolithic material shows significant promise for advanced separation science, particularly in bioanalytical applications.