Capillary electrophoresis coupled to mass spectrometry is a power tool in untargeted metabolomics studies to analyze charged and polar compounds. However, identification is a challenge due to the variability of migration times and the lack of MS/MS spectra in CE-TOF-MS, the type of instruments most frequently employed.

We present here a CE-MS search platform incorporated in CEU Mass Mediator to annotate metabolites with a confidence level L2. For its the development we analyzed 226 compounds using two fragmentor voltages: 100 and 200 V. The information obtained, such as relative migration times (RMT) and in-source fragments, were incorporated into the platform. In addition, we validated the CE-MS search functionality using different types of biological samples such as plasma samples (human, rat, and rabbit), mouse macrophages, and human urine. The RMT tolerance percentage for the search of metabolites has been determined, establishing 5% for all compounds, except for the compounds migrating in the electro-osmotic flow, for which the tolerance should be of 10%.

It has also been demonstrated the robustness of the in-source fragmentation, which makes possible the annotation of compounds by means of their fragmentation pattern. As an example, 3-methylhistidine and 1-methilhistidine, whose RMT are very close, have been annotated. Studies of the fragmentation mechanisms of acyl-L-carnitines have shown that in-source fragmentation follows the general fragmentation rules and is a suitable alternative to MS/MS.

毛细管电泳与质谱联用是在非目标代谢组学研究中分析带电和极性化合物的强大工具。但是，由于迁移时间的可变性以及CE-TOF-MS中缺少MS / MS谱图（最常用的仪器类型），鉴定是一项挑战。

我们在这里介绍一个结合在CEU Mass Mediator中的CE-MS搜索平台，以置信度L2注释代谢产物。对于其开发，我们使用两个分段电压（100和200 V）分析了226种化合物。所获得的信息（例如相对迁移时间（RMT）和源内碎片）已整合到平台中。此外，我们使用不同类型的生物样品（例如血浆样品（人，大鼠和兔子），小鼠巨噬细胞和人尿）验证了CE-MS的搜索功能。确定了代谢物搜寻的RMT耐受百分比，对于所有化合物确定为5％，但在电渗流中迁移的化合物的耐受性应为10％。

还已经证明了源内片段化的鲁棒性，这使得借助化合物的片段化模式对化合物进行注释成为可能。例如，已经注释了RMT非常接近的3-甲基组氨酸和1-甲基组氨酸。酰基左旋肉碱的碎裂机理研究表明，源内碎裂遵循一般的碎裂规则，是MS / MS的合适替代方法。