Gas chromatography–mass spectrometry (GC-MS) platforms are typically run in electron ionization (EI) mode for mass spectral matching and metabolite annotation. With the advent of high resolution mass spectrometry (HRMS), soft ionization techniques such as chemical ionization (CI) may provide additional coverage for compound identification. We evaluated NIST SRM 1950 pooled plasma reference sample using a HRGC-MS instrument [GC-Orbitrap-MS with electron ionization (EI), positive chemical ionization (PCI), and negative CI (NCI) capabilities] for metabolite annotation and quantification to assess the suitability of the platform for routine discovery metabolomics. Using both open source and vendor workflows, we validated the spectral matches with an in-house spectral library (Wake Forest CPM GC-MS spectral and retention time libraries) of EI-MS and CI-MS/MS spectra obtained from chemical standards. We confidently [metabolomics standards initiative (MSI) confidence level 2] identified 263, 93, and 65 metabolites using EI, PCI, and NCI modes, respectively, of which 270 metabolites (64%) were validated using our Wake Forest CPM GC-MS spectral libraries. When compared to published LC-MS-based efforts using the same NIST SRM 1950 plasma sample, there was only 17% overlap between the two platforms. In addition, the metabolomics analysis of community approved standard human plasma demonstrated the ability of EI- and CI-MS modes of analysis using a HRGC-MS platform to enable reproducible and interoperable spectral matching.

中文翻译：

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使用电子电离和化学电离的高分辨率 GC-Orbitrap-MS 代谢组学分析人血浆。

气相色谱-质谱 (GC-MS) 平台通常以电子电离 (EI) 模式运行，用于质谱匹配和代谢物注释。随着高分辨率质谱 (HRMS) 的出现，化学电离 (CI) 等软电离技术可为化合物鉴定提供更多覆盖范围。我们使用 HRGC-MS 仪器 [具有电子电离 (EI)、正化学电离 (PCI) 和负 CI (NCI) 功能的 GC-Orbitrap-MS] 评估了 NIST SRM 1950 混合血浆参考样本，以进行代谢物注释和量化以评估该平台对常规发现代谢组学的适用性。使用开源和供应商工作流程，我们验证了与从化学标准获得的 EI-MS 和 CI-MS/MS 光谱的内部光谱库（维克森林 CPM GC-MS 光谱和保留时间库）的光谱匹配。我们自信地 [代谢组学标准倡议 (MSI) 置信度 2] 分别使用 EI、PCI 和 NCI 模式鉴定了 263、93 和 65 种代谢物，其中 270 种代谢物 (64%) 使用我们的维克森林 CPM GC-MS 进行了验证光谱库。与已发表的使用相同 NIST SRM 1950 血浆样品的基于 LC-MS 的成果相比，两个平台之间只有 17% 的重叠。此外，社区批准的标准人血浆的代谢组学分析证明了使用 HRGC-MS 平台的 EI-和 CI-MS 分析模式能够实现可重现和可互操作的光谱匹配。