The opioid crisis in the United States is being fueled by the rapid emergence of new fentanyl analogs and precursors that can elude traditional library-based screening methods, which require data from known reference compounds. Since reference compounds are unavailable for new fentanyl analogs, we examined if fentanyls (fentanyl + fentanyl analogs) could be identified in a reference-free manner using a combination of electrospray ionization (ESI), high-resolution ion mobility (IM) spectrometry, high-resolution mass spectrometry (MS), and higher-energy collision-induced dissociation (MS/MS). We analyzed a mixture containing nine fentanyls and W-15 (a structurally similar molecule) and found that the protonated forms of all fentanyls exhibited two baseline-separated IM distributions that produced different MS/MS patterns. Upon fragmentation, both IM distributions of all fentanyls produced two high intensity fragments, resulting from amine site cleavages. The higher mobility distributions of all fentanyls also produced several low intensity fragments, but surprisingly, these same fragments exhibited much greater intensities in the lower mobility distributions. This observation demonstrates that many fragments of fentanyls predominantly originate from one of two different gas-phase structures (suggestive of protomers). Furthermore, increasing the water concentration in the ESI solution increased the intensity of the lower mobility distribution relative to the higher mobility distribution, which further supports that fentanyls exist as two gas-phase protomers. Our observations on the IM and MS/MS properties of fentanyls can be exploited to positively differentiate fentanyls from other compounds without requiring reference libraries and will hopefully assist first responders and law enforcement in combating new and emerging fentanyls.

中文翻译：

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使用无损离子操作结构鉴定芬太尼类似物原型的独特断裂模式离子淌度轨道阱质谱

新型芬太尼类似物和前体的迅速出现加剧了美国的阿片类药物危机，这些类似物和前体可以逃避传统的基于图书馆的筛选方法，而传统的筛选方法需要来自已知参考化合物的数据。由于新的芬太尼类似物没有参考化合物，我们检查了是否可以结合使用电喷雾电离 (ESI)、高分辨率离子淌度 (IM) 光谱、 -分辨率质谱（MS）和高能碰撞诱导解离（MS/MS）。我们分析了含有九种芬太尼和 W-15（一种结构相似的分子）的混合物，发现所有芬太尼的质子化形式均表现出两种基线分离的 IM 分布，从而产生不同的 MS/MS 模式。断裂后，所有芬太尼的两种 IM 分布均产生两个高强度片段，这是由胺位点裂解产生的。所有芬太尼的较高迁移率分布也产生了一些低强度片段，但令人惊讶的是，这些相同的片段在较低迁移率分布中表现出更高的强度。这一观察结果表明芬太尼的许多片段主要源自两种不同气相结构之一（暗示原体）。此外，增加 ESI 溶液中的水浓度相对于较高迁移率分布增加了较低迁移率分布的强度，这进一步支持芬太尼作为两种气相原聚体存在。我们对芬太尼的 IM 和 MS/MS 特性的观察可用于在不需要参考库的情况下将芬太尼与其他化合物区分开来，并有望帮助急救人员和执法部门打击新出现的芬太尼。