On-column conductivity detection in capillary-chip electrophoresis

Area of Science:

• Analytical Chemistry
• Microfluidics
• Electrochemical Sensing

Background:

• Capillary-chip electrophoresis (CCE) is a powerful separation technique.
• On-column detection in CCE often faces challenges with electrode integration and sample contamination.
• Accurate conductivity measurements are crucial for understanding buffer properties and electrokinetic phenomena.

Purpose of the Study:

• To develop and demonstrate a novel on-column conductivity detection method for capillary-chip electrophoresis.
• To achieve sensitive and reliable detection of analytes without direct electrode contact.
• To enable online monitoring of electric field strength and electroosmosis mobility.

Main Methods:

• Utilized a glass chip with a separation channel and two double-T structures for sample introduction and detection.
• Employed active coupling of the high electric field with two sensing electrodes via side detection channels.
• Measured potential difference related to local solution conductivity without direct electrode-sample contact.

Main Results:

• Achieved a detection limit of 15 microM for potassium ions in a Tris-HCl buffer.
• Demonstrated a linear detection range of 2 orders of magnitude without pre-concentration (stacking).
• Successfully used the baseline signal for online monitoring of electric field strength and electroosmosis mobility.

Conclusions:

• The developed method provides sensitive on-column conductivity detection in CCE.
• The design prevents electrode contamination and simplifies the system.
• This approach offers a versatile tool for CCE analysis and system characterization.