Electropreconcentration, gate injection, and capillary electrophoresis separation on a microchip

Area of Science:

• Analytical Chemistry
• Microfluidics
• Separation Science

Background:

• Nanochannel-based electropreconcentration is incompatible with capillary zone electrophoresis (CZE).
• This incompatibility arises from ion-depletion regions affecting separation efficiency.
• Existing methods lack integrated solutions for sample preconcentration and subsequent CE separation.

Purpose of the Study:

• To theoretically discuss and experimentally prove the incompatibility of nanochannel electropreconcentration with CZE.
• To develop a monolithic glass microfluidic chip for integrated electropreconcentration and CZE.
• To overcome the limitations imposed by ion-depletion regions during integrated separation.

Main Methods:

• Theoretical discussion and experimental validation of electropreconcentration-CZE incompatibility.
• Fabrication of a monolithic glass microfluidic chip with integrated micro/nanochannels.
• Utilizing a cross-intersection for shunting ion-depleted buffer and gate injection of preconcentrated samples.
• Monitoring solution conductivity to confirm ion-depletion region formation.

Main Results:

• Demonstrated incompatibility of nanochannel electropreconcentration with CZE.
• Developed a microfluidic chip enabling integrated electropreconcentration and CZE.
• Confirmed >20-fold conductivity decrease due to ion depletion during preconcentration.
• Achieved ~200-fold peptide preconcentration in 60s with efficient separation.

Conclusions:

• The developed microfluidic chip successfully integrates electropreconcentration and CZE.
• A novel cross-intersection design effectively compensates for ion-depletion effects.
• The integrated system provides high preconcentration factors and efficient separation of peptide mixtures.