Electrophoresis is integral to analytical
and biochemistry
experiences
in undergraduate education; however, fundamental principles of the
method are often taught in upper-level laboratories through hands-on
experiences. A laboratory activity is reported that teaches the concepts
of electrophoretic mobility and electroosmotic flow. A single reuseable
instrument, called a mini-E, costs 37 USD and consists of a DC power
supply, a voltmeter, platinum electrodes, and a chip cast in polydimethylsiloxane.
This activity uses common reagents costing only 0.02 USD per student.
Experiments are devised that allow students to investigate the properties
of electrophoretic flow and electroosmotic flow by separating the
two commonly used food dyeing agents Brilliant Blue FCF and Allura
Red AC in vinegar and in a solution of ammonium hydroxide. A dark-purple
mixture of these dyes is separated into red and blue bands that are
easily visualized. The migration order of the dyes differs when the
separation is performed under conditions of reversed polarity and
suppressed electroosmotic flow (vinegar) compared to conditions of
normal polarity and active electroosmotic flow (ammonium hydroxide).
When delivered to chemistry majors, students had a significant gain
in their ability to apply the concepts of electroosmosis and electrophoresis
to predict analyte migration. Although this activity targets upper-level
chemistry content, it can also be adapted for other laboratory experiences.