Quality control of ethanol fuel: Assessment of adulteration with methanol using 1H NMR

Recently in Brazil, a large number of severe cases of adulteration of hydrated ethyl alcohol fuel (HEAF) with methanol have been observed, causing losses to the tax authorities and consumers. A rapid and reliable analysis is demanded to assess the presence of this contaminant, whose physical and chemical properties are very similar to HEAF. The 1H Nuclear Magnetic Resonance (1H NMR) is evaluated to detect and quantify the presence of methanol as adulterant of HEAF using univariate and multivariate calibration. For univariate calibration, the ratio of the methyl area of methanol by the methylene group area was used and methanol content was easily quantified. Additionally, adulterated and unadulterated samples were successfully classified with high precision and accuracy when Discriminant Analysis coupled with Principal Component Analysis (PCA-DA) model are applied to 1H NMR data.