A Cost-Effective Microfluidic Device to Teach the Principles of Electrophoresis and Electroosmosis

A Cost-Effective Microfluidic Device to Teach the Principles of Electrophoresis and Electroosmosis

Carlos U. Herrada, St. Norbert College
Tyler A. Shaffer, West Virginia University
Avery M. Walker, West Virginia University
Laura D. Casto-Boggess, West Virginia University
Lisa A. Holland, West Virginia University
Timothy R. Johnson, West Virginia University
Megan E. Jones, West Virginia University
Yousef S. Elshamy, West Virginia University

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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.