Analysis of Selected Staling Aldehydes in Wort and Beer by GC-EI-MS/MS Using HS-SPME with On-Fiber Derivatization

Abstract

Quantification of staling aldehydes from wort and beer requires sensitive instrumental analysis. In the brewing industry, this is for the most part accomplished by gas chromatography-mass spectrometry (GC-MS) using headspace solid-phase microextraction (HS-SPME) and on-fiber derivatization (OFD) with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBHA). With respect to lipid oxidation products (e.g., (E)-2-nonenal) and minor Strecker aldehydes (e.g., methional), the sensitivity of GC-EI-MS might not be sufficient to ensure reliable quantification and long-term stability regarding method performance. To overcome these problems, an elaborate gas chromatography-electron impact-tandem mass spectrometry (GC-EI-MS/MS) methodology was implemented. GC-EI-MS/MS improved sensitivity and reduced matrix effects resulting from overlapping PFBHA-oximes (PFBOs). It enabled reliable quantification of 15 selected aldehydes in different matrices (wort, beer) across a wide concentration range (0.01 − 1000 µg/L). Extensive method validation and long-term stability testing proved excellent method performance. Lastly, direct comparison of GC-EI-MS/MS and GC-EI-MS revealed that the quantification of low abundant aldehydes via GC-EI-MS/MS is more reproducible and that lower limits of quantification were achieved.