Conventional aroma compound analysis of alcoholic spirits by gas chromatography with mass spectrometric and/or olfactometric detection (GC-MS/O) requires a certain degree of prior sample workup, typically involving sample distillation and pre-concentration. Although this approach provides a comprehensive characterisation of aroma constituents in a sample, it is not suitable for screening a large number of samples within a easily manageable timeframe. Direct injection mass spectrometry (DIMS) techniques, such as proton transfer reaction time-of-flight mass spectrometry (PTR-TOFMS), offer a complementary approach to analysing constituent aroma compounds, with reduced sample preconditioning and rapid and immediate compound detection. In the case of spirits, however, the presence of ethanol in high abundance poses an analytical challenge due to reagent ion sequestration and a concomitant saturation of ethanol-related product ions in the reaction chamber. The use of a fastGC in combination with PTR-TOFMS, which exhibits rapid runs of ca. 1 min that do not compromise analysis time, overcomes this issue by achieving an early elution of ethanol and thereafter an ethanol-free matrix for subsequently eluting compounds. This analytical configuration can be enhanced by the use of a peripheral liquid calibration unit (LCU), which vaporises volatile constituents from aqueous solutions by use of a heated chamber and a nebuliser under a high-pressure gas flow. While the intended use of the LCU is to establish stable gas concentrations for calibration of PTR-TOFMS, it can be repurposed to vaporise volatile constituents in liquid samples, such as alcoholic spirits. The present work demonstrates the combined use of an LCU with fastGC-PTR-TOFMS to directly analyse and quantify predominant aroma compounds in different alcoholic spirits; shaken, not stirred.

Shaken, not stirred – analysis of aroma compounds in alcoholic spirits through direct injection mass spectrometry

ACS Spring Meeting 2021

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