López Ricardo, Lapeña Ana Cristina, Cacho Juan, Ferreira Vicente
Department of Analytical Chemistry, Faculty of Sciences, Universidad de Zaragoza, 50009 Zaragoza, Spain.
J Chromatogr A. 2007 Mar 2;1143(1-2):8-15. doi: 10.1016/j.chroma.2006.12.053. Epub 2006 Dec 21.
The quantitative determination of wine volatile sulfur compounds by automated headspace solid-phase microextraction (HS-SPME) with a carboxen-polydimethylsiloxane (CAR-PDMS) fiber and subsequent gas chromatography-pulsed flame photometric detection (GC-PFPD) has been evaluated. The direct extraction of the sulfur compounds in 5 ml of wine has been found to suffer from matrix effects and short linear ranges, problems which could not be solved by the use of different internal standards or by multiple headspace SPME. These problems were attributed to saturation of the fiber and to competitive effects between analytes, internal standards and other wine volatiles. Another problem was the oxidation of analytes during the procedure. The reduction in sample volume by a factor 50 (0.1 ml diluted with water or brine) brought about a reduction in the amount of sulfur compounds taken in the fiber by a factor just 3.3. Consequently, a new procedure has been proposed. In a sealed vial containing 4.9 ml of saturated NaCl brine, the air is thoroughly displaced with nitrogen, and the wine (0.1 ml) and the internal standards (0.02 ml) are further introduced with a syringe through the vial septum. This sample is extracted at 35 degrees C for 20 min. This procedure makes a satisfactory determination possible of hydrogen sulfide, methanethiol, ethanethiol, dimethyl sulfide, diethyl sulfide and dimethyl disulfide. The linear dynamic ranges cover the normal ranges of occurrence of these analytes in wine with typical r2 between 0.9823 and 0.9980. Reproducibility in real samples ranges from 10 to 20% and repeatability is better than 10% in most cases. The method accuracy is satisfactory, with errors below 20% for hydrogen sulfide and mostly below 10% for the other compounds. The proposed method has been applied to the analysis of 34 Spanish wines.
采用涂有碳分子筛-聚二甲基硅氧烷（CAR-PDMS）涂层的纤维进行自动顶空固相微萃取（HS-SPME），随后结合气相色谱-脉冲火焰光度检测（GC-PFPD）对葡萄酒中的挥发性硫化物进行了定量测定评估。已发现直接萃取5 ml葡萄酒中的硫化物会受到基质效应和线性范围短的影响，这些问题无法通过使用不同的内标或多次顶空SPME来解决。这些问题归因于纤维的饱和以及分析物、内标和其他葡萄酒挥发物之间的竞争效应。另一个问题是分析过程中分析物的氧化。将样品体积减少50倍（用水或盐水稀释至0.1 ml），纤维中摄取的硫化物量仅减少3.3倍。因此，提出了一种新方法。在一个装有4.9 ml饱和NaCl盐水的密封小瓶中，先用氮气彻底置换空气，然后用注射器通过小瓶隔膜进一步加入葡萄酒（0.1 ml）和内标（0.02 ml）。此样品在35℃下萃取20分钟。该方法能够令人满意地测定硫化氢、甲硫醇、乙硫醇、二甲基硫醚、二乙基硫醚和二甲基二硫醚。线性动态范围涵盖了这些分析物在葡萄酒中的正常含量范围，典型的r2在0.9823至0.9980之间。实际样品的重现性在10%至20%之间，大多数情况下重复性优于10%。该方法的准确度令人满意，硫化氢的误差低于20%，其他化合物大多低于10%。所提出的方法已应用于3
4种西班牙葡萄酒的分析。
