Discovery-Based Purification of Excedrin

The separation and purification of organic mixtures are important tasks that students complete in various organic chemistry laboratory experiments. Several traditional experiments investigate simple systems and provide detailed protocols to ensure experimental success for students. In order to increase student interest and student learning, we report the development and implementation of a discovery-based laboratory project investigating the separation and purification of a poisoned Excedrin mixture. First, using chromatography and spectroscopy, students identify the components of the mixture. Second, students investigate the solubility of each component in various solvents and solutions. Finally, using the observed solubility data, students design an experimental protocol to effect separation and use this protocol to isolate and purify each component. We present our experimental design, implementation of the experiment, and analysis of student assessment of the experiment. Based on our experience, it is evident that student interest, performance, and understanding are enhanced using the discovery-based approach to the purification of Excedrin.