Comparison of solid-phase extraction sorbents for the fractionation and determination of important free and glycosidically-bound varietal aroma compounds in wines by gas chromatography-mass spectrometry

摘要

A critical comparison was made of seven solid-phase extraction (SPE) sorbents for the fractionation and isolation of 21 important free and glycosidically-bound varietal volatile aroma compounds. The sample was subjected to SPE and the free aromatics were eluted with dichloromethane followed by elution of the glucoconjugates with methanol; after fractionation, the free fraction was analyzed directly by GC-MS while the sugar-bound fraction was enzymatically hydrolyzed to liberate the free compounds before analysis by GC-MS. The extraction efficiency for the free compounds was evaluated based on the analytes’ signal recovery and for the glycosidically-bound compounds in terms of the relative peak areas. The best results for both the free and bound fractions were obtained with the Isolute ENV+ resin. Following selection of the most efficient SPE material, a GC-MS method was validated (in terms of selectivity, linearity, limits of detection (LODs) and limits of quantification (LOQs), recovery, repeatability, within-laboratory reproducibility and uncertainty) for the quantitative determination of the free primary volatiles in white wines. Validation results are presented at 4 fortification levels (10, 50, 200 and 500 μL?1). Regarding linearity, the correlation coefficient of the matrix-matched calibration plots was ≥0.99 for all the compounds. The LOQs were in the range 0.6–17.5 μg L?1. Recoveries ranged from 61% to 120% while the% relative standard deviation of the within-laboratory reproducibility was in the range 1.3% to 17.7%. Finally, the% expanded uncertainty ranged from 3.1% to 40.3%. The method has been successfully applied to the analysis of 20 white wine samples.