Online coupling of bubbling extraction with gas chromatography-mass spectrometry for rapid quantitative analysis of volatiles in beer.

Coexistence of matrices and analytes makes the analysis, determination, and quantification of volatiles in beer a tedious process that is difficult to conduct. Bubbling extraction, a newly established sample pretreatment method, directly releases analytes from liquid phase to gas phase by bubble bursting. In this study, we combined bubbling extraction with gas chromatography-mass spectrometry (GC-MS) for direct molecular characterization as well as effective qualitative and quantitative analysis of three types of fermented beers. This method was found to have a high extraction efficiency (bubbling time of 30-300 s), short analysis time (< 30 min), and rational recovery rates (85.6-97.3%) with relative standard deviations (RSDs) less than 10%. Thirteen volatiles were extracted at a wide concentration range of 0.1-10,000 ng/g with correlation coefficient (R2) > 0.990, while the limits of detection (LODs) and limits of quantification (LOQs) were found in scope of 0.001-50 ng/g. Analytical Eco-Scale, Green Analytical Procedure Index (GAPI), and Analytical Greenness (AGREE) approaches proved that our proposed method has a good greenness. In addition, Ale-type, Lambic, and Lager-type beer were successfully classified by the orthogonal partial least squares-discriminant analysis (OPLS-DA). In conclusion, bubbling extraction coupled with GC-MS has potential as a routine analysis tool for identifying volatiles in alcoholic beverages.