Pick Your Own Adventure: Orthogonal Methods for Analyzing Polyphenols

The analytical chemistry classroom is naturally poised to demonstrate the use of orthogonal techniques to quantify different molecules such as polyphenols. Using food science as a lens and a molecule-centric, inquiry-based approach, this article describes a semester-long laboratory experience for students to adapt and use potentiometric titration, spectrophotometric, and chromatographic methods to analyze polyphenols (i.e., catechin and gallic acid) in instructor-provided samples. Students then are given the agency to select a sample of interest which (theoretically) contains the target analytes (or not) and justify the appropriate method for that sample. The implementation of this experience provides students with many opportunities to authentically engage in scientific practices, such as designing experiments, evaluating their results, and making evidence-based decisions about how to modify procedures and what samples to study. After completing this laboratory experience, students reported significant gains in learning laboratory techniques and moderate gains in designing experiments and analyzing data, while engaging in authentic analyses (including variability) in a supportive environment. Peer evaluations also indicated that students had positive experiences working in groups. Furthermore, the experience is incredibly flexible. Each standard method module (titration, spectrophotometry, chromatography) can be completed independently, or more orthogonal techniques (e.g., gas chromatography) could be added to expand the molecule-centric semester experience.