Vol. 22, issue 11, article # 12

Burikov S. A., Dolenko T. A., Patsaeva S. V., Yuzhakov V. I. Diagnostics of aqueous ethanol solutions using Raman spectroscopy. // Optika Atmosfery i Okeana. 2009. V. 22. No. 11. P. 1082-1088 [in Russian].
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Abstract:

Raman scattering spectra of water-ethanol systems with various component ratios were detected in the spectral range between 200 and 4000 cm-1. Positions of Raman lines and their intensities were described and the assignment of lines was given for aqueous ethanol solutions with ethanol content ranging from 0 to 96%. It was shown that each of the intensities ICH and IOH of the stretching CH- and OH-bands normalized to the sum (ICH + IOH) depends linearly on ethanol volumetric concentration. For both modifications of experimental setup, with sequential spectra registration by photomultiplier and with parallel spectra registration by CCD-camera, the feasibility of alcohol quantification in solution was experimentally proven through measuring Raman integral intensities of stretching CH- and OH-bands. The accuracy of alcohol determination was several tenths of percent. The elaborated method can be applied in non-contact mode for ethanol quantification in aqueous ethanol solutions, as well as in alcoholic beverages. We describe the bandshape transformation for stretching OH-band, which is inhomogeneously broadened due to intermolecular interactions of hydroxyl groups of ethanol and water. The conclusions on changes of fraction of water molecules with strong Hydrogen bonding due to alteration of ethanol concentration were made using the contour analysis of stretching OH-band. Maximal fraction of water molecules with strong Hydrogen bonding corresponds to ethanol concentration of 20…25% v/v.

Keywords:

Raman-scattering, vibrational spectroscopy, stretching band, CH- and OH-groups, Hydrogen bonding, aqueous etanol solutions, determination of alcohol concentration