On-line sample preconcentration using field-amplified stacking injection in microchip capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Separation Science
• Microfluidics

Background:

• Traditional microchip capillary electrophoresis (microCE) models channels as closed systems.
• Bulk flow dynamics in microCE intersections have been previously oversimplified.

Purpose of the Study:

• To investigate microCE channel flows as an open system.
• To develop a novel sample preconcentration scheme for enhanced microCE sensitivity.

Main Methods:

• Characterized pressure-driven flows at microCE channel intersections.
• Implemented a low-conductivity buffer plug for sample stacking in a single-cross glass chip.
• Analyzed detection sensitivity and linearity using fluorescein derivatives.

Main Results:

• Demonstrated that bulk velocity mismatches drive significant liquid transport.
• Achieved 94- to 160-fold sensitivity enhancement for fluorescein derivatives.
• Established good linearity (1-60 nM) and reproducibility (4-5% RSD) for calibration curves.

Conclusions:

• Viewing microCE channels as an open system is crucial for understanding fluid dynamics.
• The developed preconcentration scheme offers substantial sensitivity improvements for microCE.
• This technique holds promise for practical applications in miniaturized analytical instrumentation.