Univalent salts as modifiers in micellar capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Separation Science

Background:

• Capillary electrophoresis (CE) is a powerful separation technique.
• Micellar electrokinetic chromatography (MEKC) enhances separation of neutral and hydrophobic analytes.
• Optimizing MEKC requires understanding electrolyte and analyte interactions.

Purpose of the Study:

• To investigate the effect of univalent salts (LiCl, NaCl, RbCl) on the separation of 3-(4-carboxybenzoyl)-quinoline-2-carboxaldehyde (CBQCA)-labeled amino acids in sodium dodecyl sulfate (SDS) micellar CE.
• To correlate salt properties (hydrodynamic radius of counter-ion) and amino acid characteristics (hydrophobicity) with separation behavior.

Main Methods:

• Micellar capillary electrophoresis (MEKC) was employed.
• CBQCA derivatization was used for amino acid labeling.
• Capacity factors were measured across varying salt concentrations (10-50 mM) in the SDS background electrolyte.

Main Results:

• Analyte-micelle affinities decreased with increasing salt concentration, most significantly with LiCl (smallest hydrodynamic radius).
• Hydrophobic interactions between analytes and micelles were stronger than hydrophilic interactions and were enhanced by smaller counter-ions.
• No adverse effects from Joule heating or electromigrative dispersion were observed at tested salt concentrations.

Conclusions:

• Univalent salts can be practically used to modulate analyte-micelle affinities for improved separation of complex mixtures in MEKC.
• Salt counter-ion size and analyte hydrophobicity are key factors influencing separation efficiency.
• This method offers a viable strategy for optimizing separation in CE applications.