Solid phase “on-situ” quadraplex isotope dimethyl labeling for the analysis of biogenic amines in beers by liquid chromatography-high resolution mass spectrometry

A simple magnetization method was developed for the preparation of magnetic materials from conventional solid phase packing though coprecipitation and solvothermal approaches. And the prepared magnetic materials were used for magnetic solid phase extraction (MSPE) of biogenic amines (BAs) from beers. Furthermore, to improve the analytical throughput, a solid phase “on-situ” quadraplex isotope dimethyl labeling method was developed for the quantification of BAs by liquid chromatography-high resolution mass spectrometry (LC HRMS). Compared to conventional in-solution labeling, the “on-situ” labeling could simplify the sample preparation procedure and efficiently remove the residuals such as inorganic salts and excessive labeling reagents. The quadraplex labeling, which enabled three real samples and one internal standard sample to be analyzed simultaneously in a single LC HRMS run. For the tested 8 BAs (cadaverine, phenethylamine, spermine, spermidine, tyramine, histamine, putrescine and tryptamine), LODs of 0.02–0.05 μg/L and LOQs of 0.05–0.1 μg/L were achieved at good reproducibility (RSD of 0.5–4.6% and 2.2–7.0% for intra- and inter-day reproducibility, respectively). With this method, six beer samples were analyzed, and these 8 BAs were all detected in the range of low μg/L to 2.9 mg/L, which were lower than maximal residual level (MRL) required in the regulations of China and EU.