Center for Mass Spectrometry, Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, New Jersey, 07030, USA.
Department of Biology, University of Utah, Salt Lake City, UT, 84112, USA.
J Chromatogr A. 2019 Mar 29;1589:149-161. doi: 10.1016/j.chroma.2019.01.011. Epub 2019 Jan 7.
Pyrazines are an important group of natural products widely used as food additives and fragrants. Gas chromatography-mass spectrometry (GCMS) is the most widely applied analytical technique for characterization of alkylpyrazines. However, mass spectra of many positional isomers of alkylpyrazines are very similar. Consequently, an unambiguous identification of each positional isomer by spectral interpretation or database search protocols is practically unfeasible. In fact, there are many misidentifications in literature. To identify alkylpyrazines, chemists often resort to gas chromatographic retention indices (RIs). Although there are many compilations of retention indices of alkylpyrazines, these databases are often incomplete and the values reported are sometimes inconsistent. Herein, we present retention indices of fifty-six alkylpyrazines recorded on DB-1, ZB-5MS, DB-624, and ZB-WAXplus stationary phases, and compare them with those available in the NIST-2017 MS-RI database. Furthermore, we demonstrate how RI values can be used, together with mass spectral interpretations, to identify certain alkylpyrazines unambiguously.
吡嗪类化合物是一类重要的天然产物，广泛用作食品添加剂和香料。气相色谱-质谱联用（GC-MS）是用于鉴定烷基吡嗪的最广泛应用的分析技术。然而，许多烷基吡嗪的位置异构体的质谱非常相似。因此，通过光谱解释或数据库搜索协议来明确鉴定每个位置异构体实际上是不可行的。事实上，文献中存在许多错误鉴定。为了鉴定烷基吡嗪，化学家通常求助于气相色谱保留指数（RIs）。虽然有许多烷基吡嗪保留指数的汇编，但这些数据库往往不完整，报告的值有时也不一致。在此，我们展示了在 DB-1、ZB-5MS、DB-624 和 ZB-WAXplus 固定相上记录的 56 种烷基吡嗪的保留指数，并将其与 NIST-2017 MS-RI 数据库中的值进行了比较。此外，我们还展示了如何结合质谱解释，使用 RI 值来明确鉴定某些烷基吡嗪。
