毛细管电泳中的电渗流和区带展宽教材.ppt

The mathematics of bio-separations: electroosmotic flow and band broadening in capillary electrophoresis (CE) Sandip Ghosal Mechanical Engineering Northwestern University Electrophoresis Electroosmosis Thin Debye Layer (TDL) Limit Application of TDL to Electroosmosis Application of TDL to electrophoresis Capillary Zone Electrophoresis (CZE) Fundamentals Sources of Band Broadening Non uniform zeta-potentials What is “Taylor Dispersion” ? Eluted peaks in CE signals Formulation (Thin Debye Layer) Slowly Varying Channels (Lubrication Limit) Lubrication Solution Green Function Green’s Function Effective Fluidic Resistance Effective Radius Zeta Potential Application: Microfluidic Circuits Application: Flow through porous media Application: Elution Time Delays Application: Elution Time Delays Dispersion by EOF in a capillary Formulation The evolution of analyte concentration The evolution of analyte concentration Asymptotic Solution Experiments of Towns Regnier Theory vs. Experiment Conclusion The problem of EOF in a channel of general geometry and variable zeta-potential was solved in the lubrication approx. Full analytical solution requires only a knowledge of the Green’s function for the cross-sectional shape. Volume flux of fluid through any such channel can be described completely in terms of the effective radius and zeta potential. The problem of band broadening in CZE due to wall interactions was considered. By exploiting the multiscale nature of the problem an asymptotic theory was developed that provides: One dimensional reduced equations describing variations of analyte concentration. The predictions are consistent with numerical calculations and existing experimental results. Solvability Condition Advection Loss to wall Dynamics controlled by slow variables Ghosal, J. Fluid Mech. 491, 285 (2003) RUN CZE MOVIE FILES + remove 100 cm 15 cm 300 V/cm PEI 200 _ Detector Experiment 2 Anal. Chem. 64, 2473 (1992) M.O. Acknowledgement: supported by the NSF u