On the formation of conjugated linoleic acid diagnostic ions with acetonitrile chemical ionization tandem mass spectrometry.
On the formation of conjugated linoleic acid diagnostic ions with acetonitrile chemical ionization tandem mass spectrometry.
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DOI：
10.1002/rcm.1797
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发表时间：
2005-02
期刊：
影响因子：
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通讯作者：
A. L. Michaud;P. Lawrence;R. Adlof;J. T. Brenna
中科院分区：
文献类型：
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作者：
A. L. Michaud;P. Lawrence;R. Adlof;J. T. Brenna
乙腈化学电离串联质谱最近已被证明是一种快速的方法，用于识别共轭亚油酸甲酯（CLA）中的双键位置和几何形状;然而，中间体和诊断离子的结构及其形成机制尚不清楚。本文提出了一种机制，即m/z54离子（1-亚甲基亚氨基）-1-乙烯基鎓（MIE）在具有混合几何构型（cis/trans，trans/cis）的CLA中优先受到顺式双键的亲核攻击，有利于观察到的C-C裂解乙烯基到反式双键. [M+54]（+）加成产物中间体与MIE与CLA两步加成得到的杂环六元环一致。用同位素标记的CLA和乙腈进行的实验，以及MS/MS/MS实验，产生与该提议一致的数据。提出的机制也与已知的离子分子化学在较小的化合物，并解释了大多数现象与MIE-CLA离子化学。
Acetonitrile chemical ionization tandem mass spectrometry has recently been shown to be a rapid method for the identification of double-bond position and geometry in methyl esters of conjugated linoleic acids (CLAs); however, the structures of intermediate and diagnostic ions and their mechanisms of formation are not known. A mechanism is proposed here in which the m/z 54 ion, (1-methyleneimino)-1-ethenylium (MIE), undergoes nucleophilic attack preferentially by the cis double bond in CLAs with mixed geometry (cis/trans, trans/cis), favoring the observed C--C cleavage vinylic to the trans double bond. The [M+54](+) addition product intermediate is consistent with a heterocyclic six-membered ring resulting from the two-step addition of MIE to the CLA. Experiments with isotopically labeled CLAs and acetonitrile, and from MS/MS/MS experiments, yield data consistent with this proposal. The proposed mechanism is also consistent with known ion-molecule chemistry in smaller compounds, and explains most phenomena associated with MIE-CLA ion chemistry.