Quantitative analysis of alcohol–water binary solutions using Raman spectroscopy

Raman spectroscopy was used for rapid and in situ measurements of alcohols in alcohol–water binary systems. An external standard was used to eliminate factors such as laser power or instrumental effects. Band ratios between the Raman bands of the target molecule and that of acetonitrile as external standard were calculated and found to be proportional to the mass fraction of alcohol. Better linearity was achieved as compared with that in the calibration curve obtained by plotting the Raman intensity alone. The equations of the calibration curves were y=0.2747 x with R 2 of 0.9996 and y=0.2189 x+1.340×10 −3 with an R 2 of 1.000 in methanol–water and in ethanol–water binary systems, with y and x denoting the Raman intensity ratio and the mass fraction of alcohol, respectively. ► Raman spectroscopy was used for determination in alcohol–water binary systems. ► Band ratios between the Raman bands of alcohol and that of the standard were calculated. ► The band ratios was found to be proportional to the mass fraction of alcohol.