Nuclear magnetic resonance spectroscopy and magnetic resonance imaging continue to be invaluable tools for the chemist and scientists in many other disciplines as well. Thus, as is evident from the many NMR-related publications in this Journal (1–12), basic NMR and Fourier transformation concepts remain important subject matter content for undergraduate education in chemistry but are elusive to grasp for the students. In this regard, several interactive simulations on Fourier transformation based on MathCad (Parametric Technology Corporation) have appeared in this Journal (11, 12), but MathCad might not be as widespread in use and accessible as spreadsheet programs. Here we present an interactive Excel (Microsoft) spreadsheet along with a guided tutorial that demonstrates a number of basic NMR and Fourier transform concepts. Specifically, the user can
Generate free induction decays (FIDs) and study the effect of changing frequency, number of protons present, and phase setting on the FID (Figure 1).
Study the effect of applying a line broadening function on the FID.
Explore the details of obtaining a spectrum from Fourier transformation.
Explore Fourier transform artifacts from improper sampling and Fourier transforming the FID (aliasing and folding).
Figure 1. A free induction decay generated with an interactive Excel spreadsheet.
The spreadsheet was originally developed to augment an elective undergraduate course on NMR spectroscopy that was designed as a hands-on instrument workshop and has been offered during a two-week winter session. In this workshop course, students were either working with NMR simulator (Bruker–Biospin) or the NMR instrument directly to explore the results of a variety of NMR experiments with the goal to find optimized parameter sets. While the NMR simulator proved to be instructive in exploring NMR pulse programs, there remained the need to demystify some of the basic NMR processing steps including how a spectrum is actually obtained from the FID. The interactive spreadsheet filled this gap. In addition, the interactive spreadsheet could serve as a lecture demonstration or a self-guided tutorial outside of class in other undergraduate courses such as physical chemistry or instrumental methods. The spreadsheet has also served as an effective training tool as part of undergraduate research projects involving the frequent use of NMR spectroscopy.
Acknowledgment
Supported by the National Science Foundation (DUE-0408617), this report is an outcome of undergraduate laboratory curriculum development to widely incorporate NMR spectroscopy.
