Hydrodynamic injection with pneumatic valving for microchip electrophoresis with total analyte utilization

Area of Science:

• Analytical Chemistry
• Microfluidics
• Separation Science

Background:

• Microchip capillary electrophoresis (CE) requires precise sample injection for reproducible separations.
• Conventional electrokinetic injection methods can suffer from biases and limited control.

Purpose of the Study:

• To develop and evaluate a novel hydrodynamic injector for microchip CE using a pneumatic valve.
• To demonstrate reproducible and unbiased sample injection with controllable volumes.

Main Methods:

• Fabrication of polydimethylsiloxane (PDMS) microfluidic devices with integrated pneumatic valves.
• Utilizing low pressure to drive sample introduction into the separation channel.
• Dynamic coating of the separation channel and analysis of FITC-labeled amino acids via CE.

Main Results:

• Achieved reproducible injection of small sample plugs (~100 pL) with adjustable volume control.
• Demonstrated reliable operation at various frequencies with good reproducibility (RSD ≤ 3.6%).
• Obtained highly efficient separations (≥ 7.0 × 10³ theoretical plates) with no sampling bias.

Conclusions:

• The pneumatic valve-controlled hydrodynamic injector offers significant advantages over conventional CE injection techniques.
• This method enables repeatable, unbiased injections, minimal sample waste, and a high duty cycle.
• Potential applications include multidimensional separations, multiplexing, and sample-limited bioanalyses.