Light-Assisted Detection of Methanol in Contaminated Spirits

The growing market of artisanal alcoholic beverages have faced challenges to assess the quality of the commercialized products. Contaminated beverages, resulting not only from an uncontrolled production process but also from deliberate adulteration, may contain nonsafe amounts of methanol leading to risks for consumers. Ethanol and methanol share similar physical-chemical properties. Both are colorless, soluble in water, and they have very close values of density. Although analytical laboratorial methods can precisely determine the alcoholic composition, rapid distinction between them is a conundrum. This paper proposes and compares two methods that can be used to fast detect the contamination of alcoholic beverages with methanol. Despite the proximity between densities of methanol and ethanol, as well as the close refractive indexes of methanol and water, it is shown that these macroscopic parameters can be used together to analyze the beverage composition. Additionally, using the fingerprinting molecular analysis provided by Raman spectroscopy and a statistical procedure based on principal component analysis, it is shown a rapid method for the detection of methanol presence in beverages above a pre-established level, without the need for addition of any standard to the sample. The performances of both methods were tested and validated with samples containing different amounts of water, ethanol, and methanol and beverages deliberately contaminated with methanol.