Experimental studies of electroosmotic flow dynamics during sample stacking for capillary electrophoresis

Area of Science:

• Analytical Chemistry
• Separation Science
• Electrokinetic Phenomena

Background:

• Field-amplified sample stacking (FASS) is a preconcentration technique used in capillary electrophoresis.
• Understanding electroosmotic flow (EOF) is crucial for optimizing FASS efficiency.
• Previous theoretical models exist for FASS, but experimental validation of EOF dynamics is ongoing.

Purpose of the Study:

• To experimentally investigate electroosmotic flow dynamics during field-amplified sample stacking.
• To examine the effect of varying sample plug lengths on EOF and electrophoretic current.
• To compare experimental observations with existing theoretical predictions for FASS.

Main Methods:

• Utilized periodic photobleaching of a neutral fluorophore for real-time EOF monitoring at 1 Hz.
• Employed hydrodynamic injection of sample plugs with varying lengths and buffer concentrations (0.125 mM and 41.7 microM phosphate).
• Used a separation buffer of 12.5 mM phosphate and analyzed peak broadening for parabolic flow assessment.

Main Results:

• Observed significant electroosmotic flow changes, up to 100% (1.6-3.3 mm/s), with increasing sample plug lengths.
• Experimental results for EOF and electrophoretic current qualitatively matched theoretical model predictions.
• Analyzed peak broadening to investigate parabolic flow resulting from discontinuous buffer systems.

Conclusions:

• Experimental validation of theoretical models for FASS is supported by observed EOF behavior.
• Sample plug length is a critical parameter influencing EOF and electrophoretic current in FASS.
• The study provides insights into flow profiles and buffer discontinuity effects in FASS.