Color, Candy, and Chromatography: A Combined TLC and HPLC Activity for the General Chemistry Laboratory

A major challenge when designing new experiments for the general chemistry laboratory is introducing students to the necessary techniques while keeping the experiment engaging and accessible. This work presents a new multiweek activity designed to introduce students to advanced instrumentation in the form of high-performance liquid chromatography (HPLC) via a related scripted thin layer chromatography (TLC) experiment using dyes from markers and food colors. These dyes have different polarities so can be separated easily with their visual nature, making them ideal for laboratories. First, commercial food colors are introduced, which contain multiple dyes that are quantified using HPLC, and then, students build upon this in the identification and quantification of dyes on candy. These laboratories have been implemented at Concordia College over the last several years with assessment data showing student gains in the understanding of polarity and chromatography and engagement with the laboratory activity.