A Derivatized Gas Chromatographic-Mass Spectrometric Method for the Analysis of Both Isomers of Resveratrol in Juice and Wine

Abstract

A gas chromatographic-mass spectrometric method has been developed and validated for the analysis of <i>cis</i>- and <i>trans</i>-resveratrol simultaneously in matrices such as wine and grape juice. Solid phase extraction of resveratrol isomers on a C-18 column was followed by derivatization with bis-[trimethylsilyl]-trifluoroacetamide under optimized conditions followed by gas-liquid chromatography of an aliquot (1 µL) on a DB-5HT column. Selective ion monitoring was performed at ion mass 444 for quantification and using ions at mass 445 and 446 as qualifiers. Unlike other methods previously reported, this method utilizes only 1 mL of sample, has an instrument analysis time of 16 minutes, is simple, and has a detection limit as low as 10 µg/L. The utilization of the Mass Selective Detector makes it a very specific method. A survey of Ontario wines indicated that the red wines have higher concentrations of <i>trans</i>-resveratrol than those reported by previous investigators for wines of other regions. In about half, even higher concentrations of <i>cis</i>-resveratrol were measured. Since the latter was not detected in grape skins or juices, it appears to be formed from the isomerization of <i>trans</i>-resveratrol or break-down of resveratrol polymers (viniferins) during skin fermentation.