Double-cross hydrostatic pressure sample injection for chip CE: variable sample plug volume and minimum number of...

Area of Science:

• Microfluidics
• Analytical Chemistry
• Electrophoresis

Background:

• Conventional sample injection in chip CE often requires complex setups and can introduce bias.
• Minimizing electrode count and simplifying operation are key challenges in microfluidic device development.

Purpose of the Study:

• To introduce a novel, simplified sample injection method for chip capillary electrophoresis (CE).
• To demonstrate precise control over sample plug volume using hydrostatic pressure and electrokinetic force.
• To showcase the method's efficiency in enabling parallel separations with minimal electrodes.

Main Methods:

• A double-cross microchip design was employed for sample plug formation and control.
• Hydrostatic pressure, generated by emptying a waste reservoir, was used for sample loading.
• Electrokinetic force in a controlling channel adjusted sample plug volume linearly.
• A four-separation-channel chip CE system validated the injection method's performance.

Main Results:

• The hydrostatic pressure injection method allowed for linear adjustment of sample plug volume.
• Parallel sample separation was achieved in a four-channel system using only two electrodes.
• The method demonstrated sample loading free of injection bias, preserving sample composition.

Conclusions:

• This novel injection technique simplifies chip CE operation by utilizing readily generated hydrostatic pressure.
• The method offers precise control and reduces the need for multiple electrodes, facilitating complex microfluidic analyses.
• The developed technique holds significant potential for advancing miniaturized analytical systems.