An improved method for the measurement of the isotope ratio of ethanol in various samples, including alcoholic and non‐alcoholic beverages

Abstract

The isotope ratios of ethanol, an important constituent or ingredient of some foods and various beverages and fuels, provide information about biological and geographical origin and quality. We have developed an improved method for measuring the isotope ratio of ethanol in various samples by gas chromatography-high temperature conversion or combustion-isotope ratio mass spectrometry (GC-TC/C-IRMS) with headspace solid-phase microextraction (HS-SPME). A HS-SPME method was developed by optimizing several different parameters, including salt addition, incubation temperature and time, and extraction time. The HS-SPME method enabled us to determine the isotope ratio at low ethanol concentrations (0.08 mM) in 50 min with good precision (+/-0.3 per thousand for delta(13)C and +/-5 per thousand for deltaD). An advantage of this technique is that it can be adapted for use with samples which have high viscosity and contain many matrix compounds, such as alcoholic and non-alcoholic beverages.

Preliminary detection method for added rice- and sugarcane-derived brewer’s alcohol in bulk samples of sake by measurement of hydrogen, oxygen, and carbon isotopes

“…While there are a number of studies using δD or δ 18 O to analyze ethanol in alcoholic beverages via gas chromatography-high-temperature conversion-isotope ratio mass spectrometry (GC-TC-IRMS) using the headspace solid-phase microextraction method, the separation of ethanol is relatively complicated and time consuming. 13,21) Measurement via analysis of δD and δ 18 O in bulk alcoholic beverages may have the advantage of quickly screening for alcohol addition without separation of the ethanol (i.e., even in the presence of water and H/O-containing non-volatile components such as sugars). In this study, the possibility of detecting C 3 plant-and C 4 plant-derived brewer's alcohol added to sake by measurement of carbon, hydrogen, and oxygen stable isotopes is examined in bulk samples of lab-brewed sake.…”

Gas chromatography/isotope ratio mass spectrometry: Analysis of methanol, ethanol and acetic acid by direct injection of aqueous alcoholic and acetic acid samples

“…Methanol, ethanol, and acetic acid are miscible with water, which means they are not easily extracted from aqueous samples using common organic solvents. To avoid using chemical derivatization during sample preparation, many methods using solid‐phase microextraction (SPME) sample preparation techniques have been developed for gas chromatography (GC), GC/mass spectrometry (GC/MS), and GC/isotope ratio mass spectrometry (GC/IRMS) for the analysis of these types of compounds. Direct injection of aqueous or water‐rich samples of these compounds into GC, GC/MS, or GC/IRMS instruments has also been reported.…”

“…GC/IRMS is predominantly used for compound‐specific isotope analysis (CSIA) in complex mixtures because of the high separation efficiency of GC. SPME GC/IRMS methods have also been developed for the isotope ratio analysis of ethanol and acetic acid in aqueous matrices and methanol in air samples.…”

“…Methanol, ethanol, and acetic acid are important industrial chemicals and they are frequently analyzed for their stable isotope ratio signatures. For example, knowledge of the stable isotope ratios of ethanol and acetic acid can contribute to the authentication of liquors and vinegar, and thus the identification of fraud, in the food industry .…”

“…Therefore, a GC/IRMS procedure for the dilution of methanol with appropriate solvents before determination is required so that additional analysis on another elemental analyzer/IRMS (EA/IRMS) or LC/IRMS instrument is not necessary. In the reported GC/IRMS methods for the isotope ratio analysis of methanol, ethanol and acetic acid, no applications have been reported and validated that involve dilution with water‐miscible organic solvents (e.g. acetonitrile and acetone) for the GC/IRMS determination of the carbon isotope ratios of pure methanol, ethanol in liquors and acetic acid in vinegars.…”