Integration of continuous-flow sampling with microchip electrophoresis using poly(dimethylsiloxane)-based valves in a...

Area of Science:

• Analytical Chemistry
• Microfluidics
• Biotechnology

Background:

• Microchip electrophoresis requires efficient methods for introducing analytes into separation channels.
• Existing methods can be slow or lack reproducibility, limiting real-time analysis.
• Poly(dimethylsiloxane) (PDMS) is a versatile material for microfluidic device fabrication.

Purpose of the Study:

• To develop a reversibly sealed microchip device with integrated pneumatic valves for rapid analyte injection.
• To enhance the reproducibility and efficiency of sample introduction in microchip electrophoresis.
• To demonstrate the device's capability for continuous monitoring of concentration changes.

Main Methods:

• Fabrication of a microchip device with PDMS-based pneumatic valves.
• Reversible sealing of the microchip to a PDMS-coated glass substrate.
• Integration of microbore tubing for fluid and gas delivery.
• Optimization of buffer system with sodium dodecyl sulfate (SDS) for improved reproducibility.
• Characterization of valve actuation time and pushback voltage.
• Analysis of derivatized amino acids using microchip electrophoresis.

Main Results:

• Pneumatic valves actuated within hundreds of milliseconds for rapid injection.
• Addition of SDS significantly improved injection reproducibility (RSD of 0.7% for fluorescein plugs).
• Device demonstrated capability for continuous off-chip concentration monitoring with a 90-second lag time.
• Successful rapid monitoring of on-chip concentration changes was achieved.

Conclusions:

• The developed microchip device enables rapid and reproducible analyte injection for microchip electrophoresis.
• The device is suitable for continuous monitoring of both off-chip and on-chip processes.
• This technology advances real-time analytical capabilities in microfluidic systems.