Analysis of Selected Aldehydes in Packaged Beer by Solid-Phase Microextraction (SPME)-Gas Chromatography (GC)-Negative Chemical Ionization Mass Spectrometry (NCIMS)

摘要

In this work, analytical techniques were combined to produce the level of sensitivity and selectivity required for the unambiguous identification and quantification of flavor-active aldehydes present in packaged beer at the low to sub-mu g/L levels with headspace on-fiber derivatization with O-2,3,4,5,6-(pentafluorobenzyl) hydroxylamine hydrochloride (PFBHA) solid-phase microextraction (SPME) with gas chromatography (GC) negative chemical ionization mass spectrometry (NCIMS) detection. The on-fiber derivatization produced two PFBHA-oxime geometrical isomers, with each isomer containing five fluorine atoms, amenable to NCIMS mode. NCIMS was chosen specifically to take advantage of the electronegative PFBHA-oximes. The characteristic fragment ions produced were detected in selected ion monitoring mode. To increase accuracy and precision, calibration was based on the technique of standard additions along with an internal standard. The application of this methodology provided detailed monitoring of changes in the levels of aldehydes in two different brands of American light lager beers under a controlled storage temperature of 24 degrees C and a time range up to 32 weeks. Significant differences in the levels of aldehydes with low organoleptic thresholds were observed between brands. The results demonstrate the usefulness of this methodology as a sensitive, selective, simple, and robust analytical tool for the measurement of aldehydes in packaged beer at trace levels.