Gas chromatography carbon isotope ratio mass spectrometry applied to the detection of neutral alcohol in Scotch whisky: an internal reference approach

Ethanol and the volatile congeners of Scotch whisky have been analysed by GC–combustion stable isotope ratio mass spectrometry (GC–C–IRMS). Ethanol, propan-1-ol, 2-methylpropan-1-ol and methylbutan-1-ol (2- and 3-methylbutan-1-ol) have been separated using gas chromatography and their ratios of stable isotopes of carbon (13C/12C) determined by combustion isotope ratio mass spectrometry. The internal isotopic correlations for the ethanol and the congeners from the same sample were determined. A close and reproducible correlation was found for 13C/12C ratios of propan-1-ol and ethanol in authentic whisky samples and is the basis for determining the addition of neutral alcohol to whisky. Initial studies suggest that the method has the ability to detect the addition of neutral alcohol, depending on the cereal source of the whisky and neutral alcohol concerned, without the need for reference to databases.