Characterization of sulfur compounds in whisky by full evaporation dynamic headspace and selectable one-dimensional/two-dimensional retention time locked gas chromatography–mass spectrometry with simultaneous element-specific detection

Abstract

A method is described for characterization of sulfur compounds in unaged and aged whisky. The method is based on full evaporation dynamic headspace (FEDHS) of 100μL of whisky samples followed by selectable one-dimensional (1D) or two-dimensional (2D) retention-time-locked (RTL) gas chromatography (GC)–mass spectrometry (MS) with simultaneous element-specific detection using a sulfur chemiluminescence detector (SCD) and a nitrogen chemiluminescence detector (NCD). Sequential heart-cuts of the 16 sulfur fractions were used to identify each individual sulfur compound in the unaged whisky. Twenty sulfur compounds were positively identified by a MS library search, linear retention indices (LRI), and formula identification using MS calibration software. Additionally eight formulas were also identified for unknown sulfur compounds. Simultaneous heart-cuts of the 16 sulfur fractions were used to produce the 2D RTL GC-SCD chromatograms for principal component analysis. PCA of the 2D RTL GC-SCD data clearly demonstrated the difference between unaged and aged whisky, as well as two different whisky samples. Fourteen sulfur compounds could be characterized as key sulfur compounds responsible for the changes in the aging step and/or the difference between two kinds of whisky samples. The determined values of the key sulfur compounds were in the range of 0.3–210ngmL−1 (RSD: 0.37–12%, n=3).