Determination of 13C/12C Isotope Ratio in Alcohols of Different Origin by 1н Nuclei NMR-Spectroscopy

Abstract

A new express method of indirect assessment of ¹³C/¹²C isotope ratio on ¹H nuclei is developed to verify the authenticity of ethanol origin in alcohol-water-based fluids and assess the facts of various alcoholic beverages falsification. It is established that in water-based alcohol-containing systems, side satellites for the signals of ethanol methyl and methylene protons in the NMR spectra on ¹H nuclei, correspond to the protons associated with ¹³C nuclei. There is a direct correlation between the intensities of the signals of ethanol methyl and methylene protons’ ¹H- NMR and their side satellites, therefore, the data obtained can be used to assess ¹³C/¹²C isotope ratio in water-based alcohol-containing systems. The analysis of integrated intensities of main and satellite signals of methyl and methylene protons of ethanol obtained by NMR on ¹H nuclei makes it possible to differentiate between ethanol of synthetic and natural origin. Furthermore, the method proposed made it possible to differentiate between wheat and corn ethanol.