Gradient elution capillary electrochromatography and hyphenation with nuclear magnetic resonance

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Separation Science

Background:

• Nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for chemical analysis.
• Capillary electrochromatography (CEC) and capillary zone electrophoresis (CZE) are advanced separation techniques.
• Integrating separation techniques with NMR enhances analytical capabilities for complex samples.

Purpose of the Study:

• To evaluate a novel capillary NMR interface for coupling gradient CEC and CZE with NMR.
• To apply this hyphenated technique for the analysis of pharmaceuticals and food components.
• To compare the performance of gradient CEC-NMR versus isocratic CEC-NMR.

Main Methods:

• Development and utilization of a capillary NMR interface.
• Analysis of an analgesic using isocratic and gradient continuous-flow CEC-NMR.
• Separation and analysis of aspartame and caffeine using continuous flow CZE-NMR with pH-controlled elution.

Main Results:

• Gradient CEC-NMR demonstrated superior performance over isocratic CEC-NMR for analgesic analysis.
• Aspartame and caffeine were successfully separated and analyzed by CZE-NMR.
• Reversing elution order by altering pH increased sample concentration, enabling 2D TOCSY-NMR acquisition for aspartame.

Conclusions:

• The developed capillary NMR interface effectively couples gradient CEC and CZE with NMR spectroscopy.
• Gradient CEC-NMR offers enhanced analytical capabilities for pharmaceutical and food analysis.
• CZE-NMR, with pH control, facilitates detailed analysis of food ingredients like aspartame.