Capillary electrophoresis with end-capillary potentiometric detection using a copper electrode

Area of Science:

• Analytical Chemistry
• Separation Science
• Electrochemistry

Background:

• Potentiometric end-capillary detection in capillary electrophoresis (CE) allows miniaturization without compromising concentration sensitivity.
• Copper electrode-based potentiometric detection offers sensitive analysis for UV-transparent inorganic and organic ions in both direct and indirect modes.

Purpose of the Study:

• To investigate the influence of end-capillary detection geometry on performance in CE.
• To develop and assess an optimized potentiometric end-capillary detection system for anion analysis.

Main Methods:

• Utilized a copper electrode for potentiometric detection in capillary electrophoresis.
• Investigated various end-capillary detection geometries, optimizing electrode alignment and proximity to the capillary outlet.
• Constructed a novel detection cell for easy capillary exchange without electrode realignment.
• Compared performance with simultaneous on-capillary photometric detection.

Main Results:

• Achieved excellent peak shapes with an optimal configuration: a 25 µm copper electrode coaxially aligned with a 25 µm capillary, positioned ~25 µm from the capillary end.
• Demonstrated no additional peak broadening compared to photometric detection.
• Obtained low micromolar (µM) concentration limits of detection (LODs) and low amol (attomole) mass LODs.
• Successfully separated common inorganic and organic anions in a tartrate electrolyte at pH 3.

Conclusions:

• The optimized potentiometric end-capillary detection system provides sensitive and high-resolution separation of anions.
• This method is a viable and advantageous alternative for analyzing UV-transparent ions in CE.
• The developed detection cell enhances usability and reproducibility in CE applications.