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Electroosmotic capillary flow with nonuniform zeta potential

Herr1, Molho, Santiago

  • 1Stanford University, California 94305-4021, USA. aeh@leland.stanford.edu

Analytical Chemistry
|March 30, 2000
PubMed
Summary

This study analyzes electroosmotic flow (EOF) in capillaries with varied surface charge. We found that non-uniform zeta-potential distributions induce pressure gradients, affecting flow and sample dispersion in analytical systems.

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Area of Science:

  • Analytical Chemistry
  • Physical Chemistry
  • Fluid Dynamics

Background:

  • Electroosmotic flow (EOF) is crucial in microfluidic devices.
  • Non-uniform surface charge distributions can significantly alter EOF behavior.
  • Understanding these variations is key for optimizing separation techniques.

Purpose of the Study:

  • To analytically and experimentally investigate EOF in capillaries with nonuniform zeta-potential.
  • To examine induced pressure gradients caused by axial variations in wall zeta-potential.
  • To assess the impact of these variations on sample dispersion and analytical performance.

Main Methods:

  • Developed analytical models for velocity fields and sample dispersion.
  • Conducted experiments using capillaries with fractional EOF suppression via adsorbed polymers.

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  • Employed nonintrusive caged-fluorescence imaging to visualize flow fields.

    • Main Results:

    • Demonstrated that axial variations in zeta-potential induce significant pressure gradients.
    • Quantified the impact of these gradients on EOF velocity profiles.
    • Observed increased band-broadening effects due to induced pressure gradients.

    Conclusions:

    • Axial zeta-potential variations perturb EOF and create induced pressure gradients.
    • These perturbations negatively impact the performance of capillary electrokinetic chromatography and capillary zone electrophoresis.
    • Controlling surface charge uniformity is critical for precise microfluidic separations.