Quantitation of (R)- and (S)-Linalool in Beer Using Solid Phase Microextraction (SPME) in Combination with a Stable Isotope Dilution Assay (SIDA)

A stable isotope dilution assay (SIDA) was developed for the quantitation of both linalool enantiomers using synthesized [2H2]R/S-linalool as the internal standard. For enrichment of the target compound from beer, a solid phase microextraction method (SPME) was developed. In comparison to the more time-consuming extraction/distillation cleanup of the beer samples, the results obtained by SPME/SIDA were very similar, even under nonequilibration conditions. Analysis of five different types of beer showed significant differences in the linalool concentrations, which were clearly correlated with the intensity of the hoppy aroma note as evaluated by a sensory panel. In addition, significant differences in the R/S ratios were measured in the beers. The SPME/SIDA yielded exact data independently from headspace sampling parameters, such as exposure time or ionic strength of the solution. Keywords: Solid phase microextraction; SPME; stable isotope dilution analysis; SIDA; linalool; enantiomeric distribution; beer; hop aroma