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Beer's Beer Lab

Determination of Alcohol Content in Beer using Raman Spectroscopy

Learning Objectives:

  1. Understand the benefits of Raman and IR spectroscopy

  2. Differentiate similar compounds with vibration-based spectroscopy



There are a variety of analytical instruments used to quantitatively measure the concentrations of atomic and molecular components in a solution. It is common to analyze atomic species with atomic absorption and molecular species with methods such as UV-Vis, HPLC, or GC. Using such methods not only damages the original sample, but typically entails extensive sample preparation. For example, since UV-Vis measures the absorption of light both inside and outside of the visible spectrum, the species of interest sometimes must be bonded to a coloring agent to allow the user to see it. HPLC and GC have issues due to their long run times and the cleaning required after their use. 


On the other hand, vibration-based spectroscopy methods such as IR and Raman can be more efficient as they are quick and do not harm the sample. Of those two, however, Raman is often more appropriate as its signals are unaffected by water. In addition, recent advancements in Raman spectroscopy have made the process of obtaining Raman spectra fast, easy, and non-destructive.


In this lab, you will utilize Raman spectroscopy to quickly determine the mole fractions of methanol, ethanol, and water in a solution.