Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.
Rapid Commun Mass Spectrom. 2012 Apr 30;26(8):921-30. doi: 10.1002/rcm.6183.
The ozonolysis of vegetable oils has been proposed as step to functionalise unsaturated lipids for the production of bio-based chemicals and materials. The observation of ozonolysis products by mass spectrometry will facilitate mechanistic studies that are essential for the further development of industrial processes based on lipid ozonolysis.
Ozonolysis of the model lipids methyl oleate and triolein was performed and samples were taken over a range of reaction times. Ozonlysis products were separated by normal and non-aqueous reversed-phase (NARP) liquid chromatography (LC) coupled to electrospray ionization (ESI) mass spectrometry (MS) and tandem mass spectrometry (MS/MS) using a hybrid quadrupole-time of flight instrument. Post-column addition of ammonium acetate solutions aided ionization. Volatile reaction products were observed using gas chromatography/electron impact mass spectrometry (GC/MS).
Secondary ozonides, reaction intermediates and previously unreported high molecular weight product dimers were observed as intact molecular ammonium ion adducts under positive ESI. The main fragment ions obtained by MS/MS were from cleavage of the trioxolane group, loss of fatty acyl chain and fragmentation between n-8 and n-9 on the fatty acyl chain. The MS/MS spectra and exact mass measurements explain most of the ozonolysis reaction products.
LC/MS, LC/MS/MS and GC/MS results demonstrate that the products from the ozonolysis of the model lipids methyl oleate and triolein are consistent with known ozonolysis reaction pathways. LC/MS techniques using non-aqueous chromatography have permitted the direct observation of mono-, di- and tri-1,2,4-triloxanes which are the secondary ozonides formed by the ozonolysis of triolein. It was also shown that intermediates formed during the ozonolysis of triolein can combine to form high molecular weight ozonide dimers.
已经提出了植物油的臭氧化反应，作为将不饱和脂质官能化以生产基于生物的化学品和材料的步骤。通过质谱观察臭氧化产物将促进对于进一步开发基于脂质臭氧化的工业过程至关重要的机理研究。
对模型脂质甲基油酸酯和三油酸酯进行臭氧化反应，并在一系列反应时间内取样。通过正相和非水反相（NARP）液相色谱（LC）与电喷雾电离（ESI）质谱（MS）和串联质谱（MS/MS）分离臭氧化产物，使用混合四极杆-飞行时间仪器。通过柱后添加乙酸铵溶液辅助离子化。使用气相色谱/电子轰击质谱（GC/MS）观察挥发性反应产物。
在正 ESI 下，观察到次级臭氧化物、反应中间体和以前未报道的高分子量产物二聚体作为完整的分子铵离子加合物。通过 MS/MS 获得的主要碎片离子来自三恶烷基团的裂解、脂肪酸链的损失以及脂肪酸链上 n-8 和 n-9 之间的碎裂。MS/MS 光谱和精确质量测量解释了大部分臭氧化反应产物。
LC/MS、LC/MS/MS 和 GC/MS 结果表明，模型脂质甲基油酸酯和三油酸酯的臭氧化产物与已知的臭氧化反应途径一致。使用非水色谱的 LC/MS 技术允许直接观察单、二和三-1,2,4-三恶烷，它们是三油酸酯臭氧化形成的次级臭氧化物。还表明，三油酸酯臭氧化过程中形成的中间体可以结合形成高分子量臭氧化物二聚体。
