Determination of Water Content in Bioethanol Using the 1 H NMR Chemical Shift Change

Abstract

Chemical shift change in 1 H NMR spectroscopy was used to determine water content in bioethanol. As water content in ethanol is increased, the proton peaks shifted to down-field due to the change in the microstructure of the water-ethanol mixture. The linear correlation between water content and chemical shift change enables the evaluation of water content in bioethanol. Because the same relationship between chemical shift change and the water content is obtained for both ethanol and bioethanol, water content in bioethanol can be determined using the calibration curve obtained with anhydrous ethanol. The developed method was validated by comparison to the results of Karl Fischer titration and was applied to commercially available bioethanols.