Remote determination of concentration of organic solvents in binary mixtures using Raman spectroscopy
S.V. Patsaeva, T.A. Dolenko, S.A. Burikov, V.I. Yuzhakov
Lomonosov Moscow State University, GSP-1, 1/2 Leninskie Gory, Moscow, 119991, Russian Federation
Keywords: Raman scattering, СН- and ОН-groups, aqueous solutions, organic solvents, determination of concentration
Abstract
Binary mixtures of methanol, ethanol, isoamyl alcohol, and acetic acid with water in various proportions have been studied using Raman spectroscopy. Upon variations in organic solvent concentration in water changes in intensities ratio for bands of СН- and ОН-group stretching vibrations within a spectral range 2600-3800 cm-1 were observed. For quantitative characterization of partial concentrations of solvents mixed with water, we have chosen an integral intensity ICH of CH-stretching band, normalized to the sum (ICH + IOH) of both СН- and ОН-group stretching bands taken within the 2600-3800 cm-1 wavenumber interval. Using this type of intensity normalization, we get the value ICH/( ICH + IOH) which depends linearly on the volume fraction of an organic solvent in aqueous solution throughout the whole studied range of its concentration. Raman spectroscopy with normalization to sum of both CH- and ОН-group stretching bands gives possibility of non-contact detection and quantification of flammable or toxic liquid mixed with water. Relative accuracy of concentration determination for ethanol, methanol, and acetic acid in water was achieved as good as 0.5, 1.1, and 1.5%, respectively.
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