Insights into cyclodextrin interactions during sample stacking using capillary isotachophoresis with on-line...

Area of Science:

• Analytical Chemistry
• Separation Science
• Supramolecular Chemistry

Background:

• Capillary isotachophoresis (cITP) is an electrophoretic technique for analyte concentration and separation.
• Beta-cyclodextrin (beta-CD) is a cyclic oligosaccharide known for forming inclusion complexes with various molecules.
• Understanding analyte-host interactions is crucial for pharmaceutical analysis and drug delivery.

Purpose of the Study:

• To investigate the interactions between specific pharmaceutical compounds and beta-cyclodextrin using on-line cITP-NMR.
• To evaluate the co-concentration behavior of beta-CD with analytes during cITP sample stacking.
• To characterize the impact of inclusion complex formation on analyte focusing and diffusion in cITP.

Main Methods:

• On-line coupling of capillary isotachophoresis (cITP) with Nuclear Magnetic Resonance (NMR) spectroscopy.
• Electrophoretic separation and concentration of pharmaceutical compounds: S-alprenolol, S-atenolol, R-propranolol, R-salbutamol, and S-terbutaline.
• Utilizing beta-cyclodextrin (beta-CD) as a host molecule to probe complexation during cITP.

Main Results:

• Most pharmaceutical analytes were concentrated by cITP sample stacking, achieving concentration factors of approximately 300.
• Beta-cyclodextrin (beta-CD) co-concentrated with analytes that formed strong inclusion complexes.
• A diffusional boundary formed post-focusing, restricting analyte and beta-CD diffusion.

Conclusions:

• On-line cITP-NMR is effective for studying host-guest interactions in solution.
• The extent of beta-CD co-concentration correlates with the strength of analyte-beta-CD inclusion complex formation.
• Analyte mobility and diffusion dynamics in cITP are influenced by complexation and boundary formation.