Quantitative NMR spectroscopy in the Instrumental Analysis Laboratory: Identification and Quantification of Active Ingredients in Over-the-Counter Pharmaceutical Products

Abstract

Chemistry undergraduate curricula typically place nuclear magnetic resonance (NMR) lectures under either organic chemistry or spectroscopy courses, aiming for students to acquire basic knowledge for the structure elucidation of simple organic compounds. On the other hand, NMR is frequently disregarded as a quantitative tool, while chromatographic and other spectroscopic methods (IR, UV–vis, and fluorescence) are taught for the quantification of analytes. However, in recent years, quantitative NMR (qNMR) has been increasingly used for the quantitative analysis of natural, pharmaceutical, and food products. Cheaper benchtop NMR devices (40–100 MHz) implemented in an academic and industrial environment made NMR experiments affordable. To more actively include qNMR in life science curriculum, its teaching strategies for the laboratory practice have to be developed. Following this logic, an experimental procedure for quantification of active pharmaceutical ingredients (APIs) in over-the-counter pharmaceutical products using an internal standard (IS) was designed for students in the Instrumental Analysis laboratory Bachelor course. Students were shown that, in addition to simple structure elucidation handled in theoretical classes, the identity and quantity of APIs in complex drug products can also be uncovered. The pedagogical coverage of this teaching activity includes topics such as sample preparation, NMR acquisition parameters, NMR data interpretation, and qNMR concepts.