Abstract

In this study, we demonstrate a novel approach to the detection and identification of the products of spin-trapped free radicals. Hydroxyl free radicals were generated by Fenton-based chemistry in the presence of ethanal and the spin-trapping agent N-tert-butyl-α-phenylnitrone (PBN). The resulting volatile compounds present in the reaction vial headspace were collected using thermal desorption (TD) and analysed by gas chromatography-mass spectrometry (GC-MS). Eleven compounds were detected in the headspace, and their identification was aided by using either a fluorinated or deuterated analogue of PBN as an alternative spin trap and/or deuterated ethanal (CD₃CHO) as the secondary source of free radicals. The electron-ionisation (EI) mass spectra clearly demonstrate the “capture” of methyl radicals; two of the compounds detected were identified as containing one methyl group derived from ethanal, and four were shown to contain two methyl groups. This study demonstrates that sampling the reaction headspace using TD-GC-MS is a viable method for analysing products of free radical trapping, and potentially may be applied to a wide range of free radical systems.

摘要

在这项研究中，我们展示了一种检测和鉴定自旋捕获自由基产物的新方法。通过基于芬顿化学中的乙醛和自旋捕获剂的存在产生的羟基自由基ñ -叔丁基α苯基硝酮（PBN）。使用热解吸 (TD) 收集反应瓶顶部空间中产生的挥发性化合物，并通过气相色谱-质谱 (GC-MS) 进行分析。在顶空检测到 11 种化合物，通过使用 PBN 的氟化或氘化类似物作为替代自旋阱和/或氘化乙醛（CD ₃CHO) 作为自由基的次要来源。电子电离 (EI) 质谱清楚地证明了甲基自由基的“捕获”；检测到的两种化合物经鉴定含有一个源自乙醛的甲基，另外四种被证明含有两个甲基。这项研究表明，使用 TD-GC-MS 对反应顶空进行采样是一种分析自由基捕获产物的可行方法，并且有可能应用于广泛的自由基系统。