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首页> 外文期刊>Journal of mass spectrometry: JMS >An experimental and computational study on the dissociation behavior of hydroxypyridine N-oxides in atmospheric pressure ionization mass spectrometry
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An experimental and computational study on the dissociation behavior of hydroxypyridine N-oxides in atmospheric pressure ionization mass spectrometry

机译：大气压电离质谱中羟基吡啶N-氧化物离解行为的实验和计算研究

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摘要

A tandem mass spectrometric study of protonated isomeric hydroxypyridine N-oxides was carried out with a hybrid quadrupole/time-of-flight mass spectrometer coupled with different atmospheric pressure ionization sources. The behavior observed in the collision-induced dissociation (CID) mass spectra of the parent cations, was similar irrespective of the source employed. However, there were intrinsic differences in the intensities of the two fragments observed for each isomer. The major fragment because of elimination of a hydroxyl radical, dominated the CID spectra (in contrast with weaker water loss) at different energy thresholds. Therefore, it was possible to differentiate both isomers at collision energies above 13 eV by comparing the ratio of intensities of the major fragment relative to the precursor cation. In addition, quantum chemical calculations at the B3LYP/6-31++G(d,p) level of theory were performed for the protonated isomers of hydroxypyridine N-oxide and their radical cation products in order to gain insight into the major routes of dissociation. The results suggest that dissociation from the lowest triplet excited state of the protonated species would provide a reasonable rationalization for the difference in behavior of both isomers.
机译：用混合的四极杆/飞行时间质谱仪结合不同的大气压电离源，对质子化异构体羟基吡啶N-氧化物进行了串联质谱研究。不论采用哪种来源，在母离子的碰撞诱导解离（CID）质谱图中观察到的行为都相似。但是，对于每种异构体，观察到的两个片段的强度存在内在差异。由于消除了羟基自由基，主要片段在不同能量阈值下主导了CID谱（与较弱的水分流失相反）。因此，有可能通过比较主要片段相对于前体阳离子的强度比，在13 eV以上的碰撞能量下区分两种异构体。此外，对羟基吡啶N-氧化物及其自由基阳离子产物的质子化异构体在B3LYP / 6-31 ++ G（d，p）理论水平进行了量子化学计算，以便深入了解离解。结果表明，从质子化物种的最低三重态激发态解离将为两种异构体的行为差异提供合理的合理化。

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