Mass spectrometry continues to play a very important role in research and quality control in the viticulture and oenology fields, and its analytical power is useful for structural studies on aroma, polyphenolic compounds, health benefit, customer safety and other aspects of the winemaking process [117, 118]. LC-MS has been used to analyse many stilbenes. For example, a sensitive high throughput LC-MS/ MS method for quantification of trans- and cis-resveratrol in wine samples has been elaborated and was used for the analysis and comparison of the trans- and cis-resveratrol content of 20 different Romanian wine samples . The detection limits for resveratrol by LC-MS were enhanced compared to LC-UV or LC-FD, even though this phytoalexin presents strong UV emission and fluorescence levels . A new type of ionisation method, atmospheric pressure photoionisation (APPI), has been found to be superior to other, more routinely used conventional approaches, namely electrospray (ESI) .
MS enables reductions in the process of sample preparation from extracts. For example, online-coupled LC-MS turbulent-flow chromatography (TFC) makes it possible to directly analyse wine samples in order to determine their flavonoid and resveratrol content. A sample (diluted wine) volume of 10 mL can be passed over a TFC column prior to LC-MS analysis . Direct infusion MS, which requires no prior separation or sample preparation, has also been demonstrated to be a valuable method for rapidly obtaining fingerprints of wine polyphenols in the differentiation of Beaujolais and Dornfelder selections and vintages by metabolomics .
Molecular weight information derived by MS, as well as fragmentation patterns obtained with by MS (MS/MS or MSn), can also supply important structural information for the identification of stilbenes. A detailed study of downy mildew-infected grapevine leaves by LC-MS has revealed more than 20 stilbenes that can be differentiated based on their MS and MS/MS spectra .
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