Office of Regulatory Science, Center for Food Safety and Applied Nutrition, Food and Drug Administration, College Park, MD, USA.
Lactiker Research Group, Department of Pharmacy & Food Sciences, University of the Basque Country (UPV/EHU), 01006, Vitoria-Gasteiz, Spain.
J Chromatogr A. 2020 May 24;1619:460955. doi: 10.1016/j.chroma.2020.460955. Epub 2020 Feb 7.
The complexity of determining the composition of animal tissue lipids is greatly increased by the presence of plasmalogens in which the alkyl chain is linked to glycerol by an enol ether bond instead of being esterified. Acidic methanolysis of animal tissue lipids provides the simultaneous scission of acyl and alkenyl ether moieties, but the complexity of the products of reaction poses a great challenge in their gas chromatographic analysis. Two-dimensional gas chromatography with online reduction (GC-OR × GC) provided the resolution of all components contained in acid methanolyzed animal lipids, taking advantage of the selective hydrogenation of alkenyl ether methanolysis products prior to the second-dimension separation (D). In this study, we also studied the chemical transformations occurring during the acidic methanolysis of animal lipids and the subsequent gas chromatographic analysis. In particular, we observed that using methanolysis reagents contaminated with water resulted in the undesired formation of fatty aldehydes, and we made recommendations on how to avoid these side reactions using proper methanolysis conditions. Products of acidic methanolysis were studied by GC-OR × GC, GC-MS, NMR spectroscopy, and GC with flame ionization detection (GC-FID). We defined the GC-FID elution order of animal lipid acidic methanolysis products using 100 m × 0.25 mm 100% bis(cyanopropyl)siloxane columns and two different set of elution conditions: isothermal elution at 180°C, and a temperature program optimized for dairy fats. A simple procedure for isolating dimethyl acetals (DMA) prior to GC analysis is also described.
动物组织脂质组成的复杂性由于质体醇的存在而大大增加，其中烷基链通过烯醇醚键而不是酯化与甘油相连。动物组织脂质的酸性甲醇解同时提供了酰基和烯基醚部分的断裂，但反应产物的复杂性对其气相色谱分析构成了巨大挑战。二维气相色谱与在线还原（GC-OR×GC）利用烯基醚甲醇解产物在第二维分离（D）之前的选择性加氢，提供了酸甲醇化动物脂质中所有成分的分辨率。在这项研究中，我们还研究了动物脂质酸性甲醇解过程中以及随后的气相色谱分析中发生的化学转化。特别是，我们观察到使用含有水的甲醇解试剂会导致不希望的脂肪酸醛的形成，并就如何使用适当的甲醇解条件避免这些副反应提出了建议。通过 GC-OR×GC、GC-MS、NMR 光谱和带有火焰电离检测（GC-FID）的 GC 研究了酸性甲醇解产物。我们使用 100m×0.25mm 100%双（氰丙基）硅氧烷柱和两种不同的洗脱条件（180°C 等温洗脱和优化用于乳制品脂肪的温度程序）定义了动物脂质酸性甲醇解产物的 GC-FID 洗脱顺序。还描述了一种在 GC 分析之前分离二甲缩醛（DMA）的简单程序。
