Analysis of Food Extracts with Thin Layer Chromatography: A STEM Outreach Activity

An outreach activity was developed and performed where familiar food items (e.g., beverages, leaves, vegetables, and citrus peels) were extracted with ethanol or ethyl acetate, and the extracts were analyzed through thin-layer chromatography (TLC). The purpose of this activity was to teach participants how chemistry can be used in the real world. Sixteen participants, who were in eighth-12th grade, were divided into four groups with two pairs of individuals. Each group was led by a university student researcher from the advisor's laboratory or by the advisor. The food extracts were analyzed by TLC using solvent systems composed of ethyl acetate and cyclohexane on glass-backed TLC plates with silica gel. After the TLC plates were developed in the solvent chamber, the separated components were visualized using a stain. The pairs of participants repeated the TLC experiment for a second time by choosing their own extracts from different groups to analyze. This outreach activity was deployed at Girls Inc. of San Antonio to show STEM participants how chemistry techniques (extraction and TLC analysis) can be used to separate different compounds from natural sources.