Synthetic cathinones (SCs) are a large category of new psychoactive substances (NPS), which pose a serious threat to public health due to limited information about their toxicology and pharmacology. Many SCs are closely related in their chemical structures, with some substances being positional isomers. In this study, we propose a new workflow for the identification of SC isomers using liquid chromatography-high-resolution tandem mass spectrometry (LC-HRMS) combined with electron activated dissociation (EAD) and chemometrics. The workflow was optimized using ring-substituted isomers of methylmethcathinones, methylethcathinones, and chloromethcathinones. The kinetic energy in the EAD cell was investigated at three levels (i.e., 15, 18, and 20 eV) for each group. Two data analysis methods (i.e., t-distributed stochastic neighbor embedding [t-SNE] and a Random Forest [RF] algorithm) were applied using the obtained EAD mass spectral data. The three sets of ring-substituted SCs were clearly distinguished using t-SNE and an RF algorithm. Moreover, the RF approach resulted in a 97 % classification accuracy for isomer identification using various combinations of compounds, isomers, and electron kinetic energies. This workflow was subsequentially applied to the analysis of 26 blind street samples, resulting in a 92 % classification accuracy for isomer identification. However, the accuracy varied based on the kinetic electron energy. A subset of the original data set, focusing on 15-eV data only, was used, resulting in a classification accuracy of 100 %. This study presents the first LC-HRMS workflow based on EAD and chemometrics, which resulted in a classification accuracy of 100 % of authentic street samples. The developed LC-HRMS workflow demonstrates that EAD product ions and their characteristic ion ratios can be successfully used to identify ring-substituted positional isomers of SCs.

中文翻译：

---

使用电子激活解离质谱法鉴定合成卡西酮位置异构体


合成卡西酮（SC）是一大类新型精神活性物质（NPS），由于其毒理学和药理学信息有限，对公众健康构成严重威胁。许多SC的化学结构密切相关，其中一些物质是位置异构体。在这项研究中，我们提出了一种使用液相色谱-高分辨率串联质谱（LC-HRMS）结合电子激活解离（EAD）和化学计量学来鉴定SC异构体的新工作流程。使用甲基甲卡西酮、甲基乙卡西酮和氯甲卡西酮的环取代异构体优化了工作流程。每组的 EAD 电池的动能在三个级别（即 15、18 和 20 eV）进行研究。使用获得的 EAD 质谱数据应用两种数据分析方法（即 t 分布随机邻域嵌入 [t-SNE] 和随机森林 [RF] 算法）。使用 t-SNE 和 RF 算法可以清楚地区分三组环取代的 SC。此外，RF 方法使用化合物、异构体和电子动能的各种组合进行异构体识别，分类准确率高达 97%。该工作流程随后应用于 26 个盲街样本的分析，异构体识别的分类准确率达到 92%。然而，精度根据电子动能而变化。使用原始数据集的子集（仅关注 15 eV 数据），分类准确度达到 100%。这项研究提出了第一个基于 EAD 和化学计量学的 LC-HRMS 工作流程，使真实街道样本的分类准确率达到 100%。 开发的 LC-HRMS 工作流程表明，EAD 产物离子及其特征离子比率可成功用于识别 SC 的环取代位置异构体。