Performance and selectivity of cationic nanoparticle pseudo-stationary phases in electrokinetic chromatography

Area of Science:

• Analytical Chemistry
• Separation Science
• Polymer Chemistry

Background:

• Electrokinetic chromatography (EKC) separates neutral compounds using an ionic pseudo-stationary phase (PSP).
• Anionic surfactants are common PSPs, but cationic latex nanoparticles present an alternative.
• Optimizing PSPs is crucial for enhancing EKC separation efficiency and selectivity.

Purpose of the Study:

• To synthesize and characterize cationic latex nanoparticles for use as PSPs in EKC.
• To evaluate the performance of these nanoparticles with different hydrophobic cores and cationic shells.
• To investigate the necessity of a cationic capillary coating for nanoparticle-based EKC.

Main Methods:

• Synthesis of diblock copolymers via reversible addition-fragmentation chain transfer (RAFT) polymerization.
• Self-assembly of copolymers into latex nanoparticles, characterized by diffusion NMR.
• Performance evaluation using a homologous series of ketones and linear solvation energy relationships (LSER) analysis.

Main Results:

• A cationic homopolymer capillary coating was essential to prevent band broadening.
• Nanoparticles with different cationic shells showed no significant difference in methylene selectivity or LSER parameters.
• Differences in selectivity and LSER parameters were observed based on the hydrophobic core composition.
• Cationic latex nanoparticles exhibited behavior more akin to anionic latex nanoparticles than cationic surfactants.

Conclusions:

• Cationic latex nanoparticles, when combined with a cationic capillary coating, are effective for EKC.
• Selectivity in these systems is primarily influenced by the hydrophobic core of the PSP.
• This approach provides a viable method for achieving anodic electroosmotic flow in EKC analyses.