Quantification of the biogenic phenethylamine alkaloid hordenine by LC-MS / MS in beer

Aim: The purpose of this study is to use an already established LC-MS/MS method in order to quantify the alkaloid hordenine in various beer brands. Methods: Hordenine was analyzed from 20 μl beer after addition of d4-hordenine as internal standard with an Agilent Eclipse XDB-C18, 5 μm, 4.6 x 150 mm column coupled to a Waters Acquity ultra performance LC. Three transitions in multiple reaction monitoring mode (MRM) were used for identification. One transition was applied for quantification. The internal standard d4-hordenine was synthesized by methylation of tyramine with deuterium labelled formaldehyde and sodium cyanoborhydride by reductive amination. Results and Discussion: Different types of beer have been examined by LC-MS/MS. Top fermented dark beer (Alt), Pils, Kölsch, wheat beer (Weizenbier) and malt liquor as well as other types of beer from the EU such as mixed beers (Salitos, Desperados) and non-alcoholic beers were analyzed. Up to 2 4 mg/L hordenine were found in typical German and regional beers (Alt, Pils, Kölsch); no significant differences between top-fermenting and bottom-fermenting beer types were found. In mixed beers the concentrations were similar to those of wheat beer (around 2 mg/L). The highest concentrations of hordenine (>4 mg/L) were measured in strong beers. Conclusion: Hordenine can serve as a reliable parameter to proof beer consumption.