Quantitative analysis of 3-alkyl-2-methoxypyrazines in German Sauvignon blanc wines by MDGC-MS or MDGC-MS/MS for viticultural and enological studies

摘要

A method for trace-level analysis of 3-alkyl-2-methoxypyrazines (MPs) based on mixed-bed cation-exchange solid phase extraction followed by heart-cut multidimensional gas chromatographic analysis was applied in a trial on viticultural and enological treatments of Sauvignon blanc wines produced in Germany. The quantification was based on a stable isotope dilution assay using deuterated MPs. For method comparison, detection was either with selected ion monitoring with a quadrupole mass spectrometer (MS) or after selected reaction monitoring using a triple quadrupole MS. Comparable performance for MP detection in the lower ng L-1 concentration range was found for both detection methods; however, in some cases, matrix problems could only be solved with MS/MS detection. It could be shown that MP levels varied considerably between the investigated vintages, with concentrations often well below 10 ng L-1. Leaf removal as a viticultural trial was a measure to decrease MP concentrations; however, the effects observed were low in the vintages studied here. Cold maceration and stem addition to the must were found as valuable enological means for increasing the MP concentration and improving the green sensory notes typical for cold climate Sauvignon blanc wines.