Sustained off-resonance irradiation-cross-sectional areas by Fourier transform ion cyclotron resonance mass spectrometry (SORI-CRAFTI) is an FTICR-MS strategy to collisionally activate precursor ions and then measure their ion-neutral collision cross sections, as well as those of selected products, at the same time. We benchmarked SORI-CRAFTI using protonated leucine-enkephalin, to excellent agreement (typically within 1–2%) with previous studies performed via collision-induced dissociation-ion mobility (CID-IMS). SORI-CRAFTI was then applied to alkali metal-cationized leucine-enkephalin and compared with CID-IMS via precursor/product cross-section ratios. Qualitative agreement between SORI-CRAFTI and CID-IMS was excellent (again, usually within 1–2%); however, neither SORI-CRAFTI nor CID-IMS could determine if metalated leucine-enkephalin was present in its canonical or zwitterionic form. When SORI-CRAFTI was used on [2.2.2]-cryptand+Cs⁺, SORI activation resulted in a 5% decrease in collision cross section, consistent with migration of the externally bound Cs⁺ into the cryptand’s cavity and similar to the cross section observed when electrospraying from an isopropanol-rich solvent. Thus, SORI-CRAFTI is useful for studying gas-phase ion chemistry of small- to medium-sized molecules and host–guest systems.

中文翻译：

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FTICR-MS 和 IM-MS 中碰撞诱导解离前体和产物离子的碰撞横截面测量：比较研究

傅里叶变换离子回旋共振质谱法 (SORI-CRAFTI) 的持续偏共振辐照横截面积是一种 FTICR-MS 策略，用于碰撞激活前体离子，然后测量它们的离子中性碰撞横截面，以及那些选择的产品，同时。我们使用质子化亮氨酸-脑啡肽对 SORI-CRAFTI 进行了基准测试，与之前通过碰撞诱导解离离子迁移率 (CID-IMS) 进行的研究非常一致（通常在 1-2% 范围内）。然后将 SORI-CRAFTI 应用于碱金属阳离子化亮氨酸-脑啡肽，并通过前体/产物横截面比率与 CID-IMS 进行比较。SORI-CRAFTI 和 CID-IMS 之间的定性一致性非常好（同样，通常在 1-2% 之内）；然而，SORI-CRAFTI 和 CID-IMS 都无法确定金属化亮氨酸-脑啡肽是否以其典型或两性离子形式存在。当 SORI-CRAFTI 用于 [2.2.2]-cryptand+Cs⁺，SORI 活化导致碰撞横截面减少 5%，这与外部结合的 Cs ⁺迁移到穴状体腔中一致，并且类似于从富含异丙醇的溶剂中电喷雾时观察到的横截面。因此，SORI-CRAFTI 可用于研究中小型分子和主客体系统的气相离子化学。