A Case Study In Using 1H NMR Analysis To Identify Compounds In Scotch and Mezcal

Abstract

Verifying to what extent H1 NMR is a useful stand-alone analytical method to examine scotch whisky and mezcal is important now because premium beverages are the quickest growing segment of alcohol purchasing in the USA. Desktop NMR is widespread and accessible as a layman’s analytical device in the wine industry. With an 800MHz NMR, I identified α-glucose and ß-glucose in each of 6 scotch brands. Also, a mono-substituted benzene derivative is present in all 11 samples, both in scotch and in mezcal. The methodology tested here to comparatively analyze scotch and mezcal using 1H NMR is conceptually sound. I examine 6 scotches and 5 mezcals. Because both beverages are high-ethanol and high-water concentration liquids, I followed the standard practice of signal suppression to collect my specta, thus revealing the lower-concentration compounds. My analytic methodology is two-fold. Along the first line, I identify compounds known to be in these alcoholic beverages from prior knowledge in the field, next I develop expectations about their H1 NMR signals in H2O/D2O solvent, and finally I search for these signal patterns in my spectra. Along the second line, I identify regions of interest in my spectra. These regions of interest are areas of the spectra that appear different between one brand and another brand -or- that appear consistently different when comparing a scotch with a mezcal. This senior thesis provides useful Appendixes of Predicted Spectra and regions of interest in mezcal spectra. With these tools and this verified methodology, one has an ability to quickly identify compounds in these spirits.