Analysis of triacylglycerol (TG) and phospholipid sn-positional isomers can be divided into two main categories: (a) direct separation by chromatography or other means such as ion mobility mass spectrometry and (b) quantification of regioisomer ratios by structurally informative fragment ions with mass spectrometric methods. Due to long retention times and limited performance, researchers are moving away from direct chromatographic separation of isomers, using mass spectrometry instead. Many established analytical methods are targeting specific isomers of interest instead of untargeted analysis of comprehensive profiles of regioisomers. Challenges remain arising from the large number of isobaric and isomeric lipid species in natural samples, often overlapping chromatographically and sharing structurally informative fragment ions. Further, fragmentation of glycerolipids is influenced by the nature of the attached fatty acids, and the lack of available regiopure standards is still an obstacle for establishing calibration curves required for accurate quantification of regioisomers. Additionally, throughput of many methods is still quite limited. Optimization algorithms and fragmentation models are useful especially for analysis of TG regioisomers, as identification using calibration curves alone without proper separation is difficult with complex samples.

中文翻译：

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液相色谱和质谱法分析甘油三酯和磷脂顺位异构体

三酰甘油 (TG) 和磷脂sn-的分析位置异构体可分为两大类：(a) 通过色谱法或离子淌度质谱法等其他手段直接分离，以及(b) 通过具有结构信息的碎片离子和质谱法对区域异构体比率进行量化。由于保留时间长且性能有限，研究人员正在放弃异构体的直接色谱分离，而改用质谱法。许多已建立的分析方法针对感兴趣的特定异构体，而不是对区域异构体的综合概况进行非靶向分析。自然样品中存在大量同量异位和同分异构的脂质物质，这些物质通常在色谱上重叠并共享结构信息片段离子，因此仍然存在挑战。更远，甘油脂的裂解受所附脂肪酸的性质影响，缺乏可用的区域纯标准品仍然是建立准确定量区域异构体所需的校准曲线的障碍。此外，许多方法的吞吐量仍然非常有限。优化算法和裂解模型特别适用于 TG 区域异构体的分析，因为复杂样品很难单独使用校准曲线进行鉴定而没有适当的分离。