An Advanced Spectroscopy Lab That Integrates Art, Commerce, and Science as Students Determine the Electronic Structure of the Common Pigment Carminic Acid

Abstract

Carminic acid and its metal derivatives have been used widely as pigments for fabrics and art, and more recently as a colorant for food. An undergraduate teaching laboratory is described in which students are instructed to design and execute experimental studies to obtain detailed information about the electronic structure, metal complex formation, redox properties, and photochemical stability of extracted carminic acid. The lab maintains room for student innovation and is well-suited to upper-level undergraduates in an advanced spectroscopy lab. Students are invited to apply knowledge previously gained through highly directed experiments to the analysis of an unfamiliar, complex, and relevant problem. The laboratory lends itself to flexibility in implementation but is designed to deepen students’ understanding of UV–vis spectroscopy, fluorescence spectroscopy, IR spectroscopy, electrochemistry, pH and metal spectrophotometric titrations, and experimental determination of the kinetic behavior of UV-induced decomposition.