Ion-molecule adduct formation in tandem mass spectrometry
Ion-molecule adduct formation in tandem mass spectrometry
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DOI：
10.1007/s00216-015-9237-6
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发表时间：
2016-02-01
影响因子：
4.3
通讯作者：
Teresa Galceran, Maria
中科院分区：
文献类型：
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作者：
Alechaga, Elida;Moyano, Encarnacion;Teresa Galceran, Maria
现在大多数LC-MS方法依赖于串联质谱，不仅用于通过多反应监测（MRM）定量和确认化合物，而且用于从其产物离子光谱中识别未知物。然而，在质量分析器内部的带电和中性物质之间可能发生气相反应，产生m/z值高于前体离子的m/z值的产物离子，或者产生难以通过逻辑损失解释的m/z值的产物离子，这使得质谱解释复杂化。在这项工作中，形成的加合物离子的质量分析仪进行了研究，使用几个质谱仪与不同的质量分析仪（离子阱，三重四极杆，四极杆轨道阱）。选择杂环胺（A α C、MeA α C、Trp-P-1和Trp-P-2）、光引发剂（BP和THBP）和药物（非那西丁和左旋咪唑）作为模型化合物，并使用电喷雾作为电离方法注入LCQ Classic、TSQ Quantum Ultra AM和Q-Exactive Orbitrap（ThermoFisher Scientific）质谱仪中。离子-分子加合物的生成取决于化合物和所用的仪器。与中性有机溶剂（甲醇和乙腈）的加合物仅在离子阱仪器（LCQ Classic）中观察到，因为电离源轴上配置和缺乏气相屏障，这允许中性物质惯性进入分析仪。三重四极杆仪器中的加合物形成（仅与水）比离子阱和四极杆-Orbitrap质谱仪中的要少，因为反应产物离子在质量分析仪中的停留时间较短。CID和/或阻尼气体的水分水平在梁状质量分析仪（例如三重四极杆）中具有很大影响，但在阱状质量分析仪中没有影响，这可能是因为即使在质谱仪内具有非常低浓度的水的情况下也允许形成加合物的长停留时间。
Nowadays most LC-MS methods rely on tandem mass spectrometry not only for quantitation and confirmation of compounds by multiple reaction monitoring (MRM), but also for the identification of unknowns from their product ion spectra. However, gas-phase reactions between charged and neutral species inside the mass analyzer can occur, yielding product ions at m/z values higher than that of the precursor ion, or at m/z values difficult to explain by logical losses, which complicate mass spectral interpretation. In this work, the formation of adduct ions in the mass analyzer was studied using several mass spectrometers with different mass analyzers (ion trap, triple quadrupole, and quadrupole-Orbitrap). Heterocyclic amines (A alpha C, MeA alpha C, Trp-P-1, and Trp-P-2), photo-initiators (BP and THBP), and pharmaceuticals (phenacetin and levamisole) were selected as model compounds and infused in LCQ Classic, TSQ Quantum Ultra AM, and Q-Exactive Orbitrap (ThermoFisher Scientific) mass spectrometers using electrospray as ionization method. The generation of ion-molecule adducts depended on the compound and also on the instrument employed. Adducts with neutral organic solvents (methanol and acetonitrile) were only observed in the ion trap instrument (LCQ Classic), because of the ionization source on-axis configuration and the lack of gas-phase barriers, which allowed inertial entrance of the neutrals into the analyzer. Adduct formation (only with water) in the triple quadrupole instruments was less abundant than in the ion trap and quadrupole-Orbitrap mass spectrometers, because of the lower residence time of the reactive product ions in the mass analyzer. The moisture level of the CID and/or damper gas had a great effect in beam-like mass analyzers such as triple quadrupole, but not in trap-like mass analyzers, probably because of the long residence time that allowed adduct formation even with very low concentrations of water inside the mass spectrometer.