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首页> 外文期刊>Journal of mass spectrometry: JMS >Electron ionization LC-MS with supersonic molecular beams-the new concept, benefits and applications
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Electron ionization LC-MS with supersonic molecular beams-the new concept, benefits and applications

机译：具有超音速分子束的电子电离LC-MS-新概念，优势和应用

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A new type of electron ionization LC-MS with supersonic molecular beams (EI-LC-MS with SMB) is described. This system and its operational methods are based on pneumatic spray formation of the LC liquid flow in a heated spray vaporization chamber, full sample thermal vaporization and subsequent electron ionization of vibrationally cold molecules in supersonic molecular beams. The vaporized sample compounds are transferred into a supersonic nozzle via a flow restrictor capillary. Consequently, while the pneumatic spray is formed and vaporized at above atmospheric pressure the supersonic nozzle backing pressure is about 0.15Bar for the formation of supersonic molecular beams with vibrationally cold sample molecules without cluster formation with the solvent vapor. The sample compounds are ionized in a fly-though EI ion source as vibrationally cold molecules in the SMB, resulting in Cold EI' (EI of vibrationally cold molecules) mass spectra that exhibit the standard EI fragments combined with enhanced molecular ions. We evaluated the EI-LC-MS with SMB system and demonstrated its effectiveness in NIST library sample identification which is complemented with the availability of enhanced molecular ions. The EI-LC-MS with SMB system is characterized by linear response of five orders of magnitude and uniform compound independent response including for non-polar compounds. This feature improves sample quantitation that can be approximated without compound specific calibration. Cold EI, like EI, is free from ion suppression and/or enhancement effects (that plague ESI and/or APCI) which facilitate faster LC separation because full separation is not essential. The absence of ion suppression effects enables the exploration of fast flow injection MS-MS as an alternative to lengthy LC-MS analysis. These features are demonstrated in a few examples, and the analysis of the main ingredients of Cannabis on a few Cannabis flower extracts is demonstrated. Finally, the advantages of EI-LC-MS with SMB are listed and discussed. Copyright (c) 2015 John Wiley & Sons, Ltd.
机译：描述了一种具有超音速分子束的新型电子电离LC-MS（具有SMB的EI-LC-MS）。该系统及其操作方法基于：在加热的喷雾汽化室中LC液体流的气动喷雾形成，完全样品热汽化以及随后在超音速分子束中振动的冷分子的电子电离。汽化的样品化合物通过限流毛细管转移到超音速喷嘴中。因此，当在高于大气压的压力下形成并蒸发气动喷雾时，超音速喷嘴的背压约为0.15Bar，以形成具有振动冷样品分子的超音速分子束，而不会与溶剂蒸汽形成团簇。样品化合物在SMB中通过振动的冷分子在飞速EI离子源中被电离，从而产生冷EI'（振动冷分子的EI）质谱图，该质谱图显示了标准EI片段与增强的分子离子的结合。我们评估了具有SMB系统的EI-LC-MS，并证明了其在NIST库样品鉴定中的有效性，并补充了增强型分子离子的可用性。带有SMB系统的EI-LC-MS具有五个数量级的线性响应和统一的化合物独立响应（包括非极性化合物）。此功能改善了样品定量，无需化合物特异的校准即可近似。像EI一样，冷EI没有离子抑制和/或增强作用（困扰ESI和/或APCI），这有助于更快的LC分离，因为完全分离不是必需的。由于没有离子抑制效应，因此可以探索快速流动进样MS-MS，以替代冗长的LC-MS分析。在一些示例中演示了这些功能，并演示了对几种大麻花提取物上大麻的主要成分的分析。最后，列出并讨论了带有SMB的EI-LC-MS的优点。版权所有（c）2015 John Wiley＆Sons，Ltd.

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