Abstract Recently glow discharge (GD) mass spectrometry, which is conventionally used to analyze solid samples, was successfully applied for ionization and the subsequent determination of volatile organic compounds (VOCs). In the present study, the possibility of direct determination of VOCs in ambient air using time-of-flight mass spectrometry with microsecond pulsed discharge in a copper hollow cathode was considered for the first time. The discharge cell of the mass spectrometer was modified for the direct analysis of gaseous samples by the introduction of a quartz capillary into the argon input channel. Various classes of compounds (aromatic and aliphatic hydrocarbons and derivatives of carboxylic acids) were studied. Particular attention was paid to the ionization mechanisms of VOCs. New mechanisms of chemical and electron ionization, resulting in the formation of associate ions with cathode material (copper) – CuM+, were demonstrated and implemented. Alternative mechanisms of organic compounds ionization in GD may be related to Penning process and proton transfer reactions. These processes are mainly responsible for the formation of molecular and protonated molecular ions. The relative contribution of all these mechanisms can be adjusted by operating parameters. In general, an extremely low degree of fragmentation of molecular ions or associates was observed. Due to its isotopic structure (only two isotopes 63Cu and 65Cu with comparable abundances), the use of copper as cathode material additionally increases the reliability of VOC identification in the form of their CuM+ associates. Such association shifts the detected ions to the region of large masses with fewer interferences and noise related to scattered ions.

中文翻译：

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铜空心阴极微秒脉冲辉光放电揭示了一种电离和测定挥发性有机化合物的新方法

摘要 最近，通常用于分析固体样品的辉光放电 (GD) 质谱已成功应用于电离和随后的挥发性有机化合物 (VOC) 的测定。在本研究中，首次考虑了在铜空心阴极中使用微秒脉冲放电飞行时间质谱直接测定环境空气中 VOC 的可能性。通过将石英毛细管引入氩气输入通道，质谱仪的放电室被修改为直接分析气态样品。研究了各种类型的化合物（芳香族和脂肪族烃以及羧酸的衍生物）。特别关注 VOC 的电离机制。化学和电子电离的新机制，导致与阴极材料（铜）-CuM+ 形成缔合离子的方法得到了证明和实施。GD 中有机化合物电离的其他机制可能与 Penning 过程和质子转移反应有关。这些过程主要负责形成分子和质子化的分子离子。所有这些机制的相对贡献可以通过操作参数进行调整。通常，观察到分子离子或缔合物的碎裂程度极低。由于其同位素结构（只有两种同位素 63Cu 和 65Cu 具有可比的丰度），使用铜作为阴极材料还增加了以 CuM+ 关联物形式识别 VOC 的可靠性。