Quantitative determination of ethanol in cider by 1H NMR spectrometry

A quantitative determination method of ethanol in cider is proposed by means of the proton nuclear magnetic resonance (1H NMR) technique. Ethanol gives a triplet signal at 1.18 ppm in the spectrum, and its area is used to determine the concentration of this compound. 3-(Trimethylsilyl)-2,2,3,3-d4-propionic acid sodium salt is added to the cider with a double purpose: as a reference for 0.00 ppm and as an internal standard for 1H NMR measurement. Gas chromatography is used to validate the method. A good correlation is found between the ethanol concentrations obtained by 1H NMR and by gas chromatography in different commercial ciders. The 95% confidence interval for the slope is 1.07 ± 0.12 (includes 1) and for the intercept −0.03 ± 0.63 (includes 0). The described method is fast and direct.