Comparative study of floating and dynamic injection modes in electrokinetic separative microsystems.

Area of Science:

• Analytical Chemistry
• Microfluidics
• Separation Science

Background:

• Miniaturization of analytical instruments is a key trend in analytical chemistry.
• Microchip-based analytical devices offer advantages like reduced reagent use and faster analysis.
• Efficient sample injection is crucial for sensitive and effective separations in microchips.

Purpose of the Study:

• To compare the performance of dynamic electrokinetic injection versus floating electrokinetic injection in microchip separations.
• To evaluate injected amount, reproducibility, separation efficiency, and analyte discrimination between the two injection modes.
• To validate experimental findings with numerical simulations.

Main Methods:

• Utilized a cross-junction microchip design fabricated from PDMS-glass.
• Performed zonal electrophoresis analysis of five derivatized amino acids.
• Conducted experiments and numerical simulations to assess injection modes.

Main Results:

• Dynamic injection significantly reduces total analysis time by a factor of two compared to floating injection.
• Dynamic injection demonstrates superior reproducibility, with RSD of peak areas at 1.3% versus 10% for floating injection.
• Dynamic injection achieves approximately 20% more efficient separation due to reduced sample plug dispersion.

Conclusions:

• Dynamic electrokinetic injection is more suitable for microchip-based separations than floating injection.
• The dynamic mode offers substantial improvements in speed, reproducibility, and separation efficiency.
• Experimental results align well with numerical simulations, confirming the advantages of dynamic injection.