Designing Undergraduate Chemistry Experiments to Address Public Concerns: Exploring the Properties of Expired and Expiring Ibuprofen

Abstract

The outbreak of the COVID-19 pandemic has led to the irrational hoarding of medicine, resulting in public confusion over the safety of expired medicine in the post-pandemic era. This paper aims to stimulate the interest of chemistry students through an undergraduate teaching experiment and employs the knowledge acquired to address societal concerns. It centers on ibuprofen, a typical antipyretic medication. We employed a range of analytical methods to qualitatively and quantitatively analyze the changes after medicine expires. The experiment is designed to evoke theoretical knowledge such as analytical chemistry, pharmaceutical chemistry, and spectral analysis acquired by undergraduate students with a chemistry major background and demonstrates how to apply these professional skills to solve realistic problems. First, we utilized Infrared Absorption Spectrometry (IR) to detect the fundamental structure of ibuprofen. Based on the obtained Infrared Spectra, we confirmed that the basic structures of ibuprofen remained intact both before and after expiration. However, IR could only facilitate qualitative analysis and did not provide information on content changes. Therefore, we also employed Ultraviolet-Visible Absorption Spectrometry (UV/Vis) and Acid-Base Titration to quantitatively analyze the benzyl and carboxyl groups in ibuprofen molecules. And uncovered the molecular-level changes that occur during medicine expiration. The structure of ibuprofen post-expiration remained, but the content of benzyl and carboxylic groups decreased, with the reduction becoming more pronounced as expiration time increased. This experimental teaching attempt provides an example of exploring the chemical properties of substances related to public health, which fits into analytical chemistry experimental courses.