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Related Experiment Videos

On-chip millionfold sample stacking using transient isotachophoresis.

Byoungsok Jung1, Rajiv Bharadwaj, Juan G Santiago

  • 1Department of Mechanical Engineering, and Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA.

Analytical Chemistry
|April 4, 2006
PubMed
Summary

We developed a robust isotachophoresis (ITP) method integrated with capillary electrophoresis (CE) for millionfold sample stacking. This technique enhances detection sensitivity for trace analytes in microchip devices.

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Area of Science:

  • Analytical Chemistry
  • Separation Science
  • Microfluidics

Background:

  • Capillary electrophoresis (CE) offers high separation efficiency but often suffers from limited sample loading capacity and sensitivity.
  • Trace analyte detection in complex matrices remains a significant challenge in analytical chemistry.
  • Sample preconcentration techniques are crucial for improving the limits of detection in microfluidic analytical devices.

Purpose of the Study:

  • To develop and validate a simple, robust isotachophoresis (ITP) method for significant sample stacking.
  • To integrate the ITP method with microchip-based capillary electrophoresis (CE) for enhanced sensitivity.
  • To investigate the effects of key experimental parameters on ITP stacking performance.

Main Methods:

  • A single-column isotachophoresis (ITP) configuration was employed.

Related Experiment Videos

  • Electroosmotic flow suppression and high leading ion concentrations were utilized for optimized ITP.
  • Parametric studies were conducted on initial sample ion concentration, leading ion concentration, and trailing ion concentration.
  • A one-dimensional nondispersive model and scaling analysis were used to evaluate dispersion.

    • Main Results:

    • Achieved millionfold (up to 2 x 10^6) sample concentration increase using ITP.
    • Demonstrated sensitive detection of 100 fM Alexa Fluor 488 with a signal-to-noise ratio of 11.
    • Successfully stacked and separated negatively charged fluorescent tracers (Alexa Fluor 488 and bodipy) with concentration factors up to 6.4 x 10^4.
    • Showcased integration with standard microchannel designs and off-the-shelf instrumentation.

    Conclusions:

    • The developed ITP method provides a simple and robust approach for significant sample stacking.
    • ITP/CE integration effectively enhances sensitivity for trace analyte detection in microfluidic systems.
    • The protocol is readily implementable with existing microchip CE platforms and buffer systems.