A new sequential injection analysis-capillary electrophoresis system with amperometric detection

Area of Science:

• Analytical Chemistry
• Electrochemistry
• Separation Science

Background:

• Automated analytical systems are crucial for high-throughput and reproducible measurements.
• Capillary electrophoresis (CE) coupled with amperometric detection offers high sensitivity but can face challenges with automation and high-voltage interfacing.
• Sequential injection analysis (SIA) provides a platform for automated sample handling and reagent manipulation.

Purpose of the Study:

• To develop a fully automated sequential injection analysis (SIA) manifold integrated with capillary electrophoresis (CE) and amperometric detection.
• To address challenges in interfacing high-voltage CE with flow-based SIA systems.
• To establish a robust and reliable method for quantifying electroactive analytes.

Main Methods:

• Designed a novel SIA manifold with an air plug to isolate the system from CE high voltage.
• Implemented a hydrodynamic injection technique based on overpressure generated by a pinch valve.
• Utilized a modified capillary union for precise alignment of the capillary and working electrode.
• Accounted for potential shifts induced by the CE separation voltage without a decoupling device.

Main Results:

• Achieved high precision for the hydrodynamic injection method with relative standard deviations (RSD) below 2.55% for peak height and 1.82% for peak area.
• Demonstrated reliable capillary and electrode alignment, yielding RSD values below 2.64% (peak height) and 2.08% (peak area) upon electrode replacement.
• Successfully quantified dopamine and epinephrine in the range of 1-500 μM with a detection limit of 0.3 μM using a gold microelectrode.

Conclusions:

• The developed automated SIA-CE-amperometric detection system is robust and reliable.
• The novel hydrodynamic injection and electrode alignment methods overcome key interfacing challenges.
• This system holds potential for developing advanced CE platforms and for online process monitoring applications.