Isotachophoresis with emulsions.

Area of Science:

• Analytical Chemistry
• Fluid Dynamics
• Physical Chemistry

Background:

• Isotachophoresis (ITP) is an electrophoretic separation technique.
• Emulsions as leading electrolytes (LE) in ITP present unique transport and flow phenomena.
• Understanding these phenomena is crucial for optimizing ITP applications.

Purpose of the Study:

• To investigate the behavior of oil droplets within an emulsion used as a leading electrolyte in ITP.
• To elucidate the role of surfactants, specifically polyvinylpyrrolidone (PVP), on droplet dynamics at the ITP transition zone.
• To explain the formation of vortices observed in the terminating electrolyte during ITP.

Main Methods:

• Experimental study of isotachophoresis (ITP).
• Utilized oil-in-water emulsions as the leading electrolyte (LE).
• Varied electrolyte composition by including or excluding surfactants (PVP).

Main Results:

• Oil droplets in the LE are collected and transported at the ITP transition zone.
• Without PVP, droplets coalesce, merge with channel walls, and form an oil film.
• With PVP, coalescence is suppressed, and droplets form an agglomerate at the transition zone.
• Two counter-rotating vortices form in the terminating electrolyte, explained by hydrodynamic instability.

Conclusions:

• Surfactants significantly influence droplet behavior in ITP systems with emulsion LEs.
• PVP addition prevents droplet coalescence and wall adhesion, promoting agglomerate formation.
• Hydrodynamic instability drives vortex formation in the terminating electrolyte during ITP experiments.