Dienstleistungszentrum Ländlicher Raum (DLR) Rheinpfalz, Abteilung Weinbau und Oenologie, Breitenweg 71, D-67435 Neustadt an der Weinstrasse, Germany.
J Chromatogr A. 2010 Oct 22;1217(43):6769-77. doi: 10.1016/j.chroma.2010.06.049. Epub 2010 Jun 25.
The analysis of 3-alkyl-2-methoxypyrazines in Vitis vinifera grape must or wine at the low nanogram per liter level failed in several situations when applying a one-dimensional gas chromatographic analysis with mass spectrometric detection (GC-MS). Sample preparation methods such as headspace solid phase microextraction or solid phase extraction were convenient procedures, however lacking extraction selectivity for complex matrices. Analysis by comprehensive two-dimensional gas chromatography with mass spectrometric detection clearly demonstrated the potential for co-elution in such matrices and the risk for erroneous results when applying one-dimensional GC-MS. In one example, matrix problems would have been a challenge even for a comprehensive two-dimensional chromatographic approach with MS detection (GC×GC-MS). A solution to matrix problems was found by protonating the 3-alkyl-2-methoxypyrazines in acidic pH and sample clean-up using solid phase extraction with a mixed-mode polymeric cation-exchange sorbent. Quantification was performed by a stable isotope dilution assay, following analysis by on-line coupled high performance liquid chromatography with multidimensional gas chromatography and detection with mass spectrometry (on-line LC-MDGC-MS). This new approach allowed trace-level analysis of 3-alkyl-2-methoxypyrazines in grape musts and wines and is described for V. vinifera Sauvignon blanc, following 3-alkyl-2-methoxypyrazines concentrations during ripening and in the processed wines.
在应用一维气相色谱分析结合质谱检测（GC-MS）时，在几种情况下，对葡萄汁或葡萄酒中的 3-烷基-2-甲氧基吡嗪进行分析时未能达到纳克/升的低水平。顶空固相微萃取或固相萃取等样品制备方法虽然方便，但对复杂基质的萃取选择性不足。通过全面二维气相色谱分析结合质谱检测分析清楚地表明，在这种基质中存在共洗脱的可能性，以及在应用一维 GC-MS 时存在错误结果的风险。在一个例子中，即使采用具有 MS 检测的全面二维色谱方法（GC×GC-MS），基质问题也将是一个挑战。通过在酸性 pH 下质子化 3-烷基-2-甲氧基吡嗪，并使用混合模式聚合物阳离子交换吸附剂进行固相萃取进行样品净化，解决了基质问题。通过在线偶联高效液相色谱与多维气相色谱和质谱检测（在线 LC-MDGC-MS）分析后，采用稳定同位素稀释分析进行定量。这种新方法允许在葡萄汁和葡萄酒中痕量分析 3-烷基-2-甲氧基吡嗪，并描述了 V.vinifera Sauvignon blanc 在成熟过程中和加工葡萄酒中的 3-烷基-2-甲氧基吡嗪浓度。
