An accurate differential analysis of carboxylic acids in beer using ultra high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry based on chiral derivatization combining three isotopic reagents.

We developed a highly sensitive and accurate differential method for analyzing chiral and achiral carboxylic acids in Japanese commercial beers, using ultra high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF-MS), based on chiral derivatization combining three isotopic chiral reagents: C-DMT-3(S)-Apy, C-DMT-3(S)-Apy, and d-DMT-3(S)-Apy. By combining these reaction solutions and analyzing the resulting mixture, simultaneous comparative analyses of the three samples could be achieved while offsetting the matrix effects on the samples. Using this approach, it was possible to differentiate the beers according to the type (draft, low-malt, and non-alcoholic), manufacturer, and storage conditions (temperature and storage period), based on the concentrations of carboxylic acids in the beers. Furthermore, we identified α-ketoglutaric acid as a new marker for determining the storage condition of Japanese beers. The proposed method would provide insights into the identification of markers in various fields, such as in biological samples, as well as food and beverages.