Abstract. Chemical ionisation inlets are fundamental instrument components in chemical ionisation mass spectrometry (CIMS). However, the sample gas and reagent ion trajectories are often understood only in a general and qualitative manner. Here we evaluate two atmospheric pressure chemical ionisation inlets (MION2 and Eisele type inlet) with computational fluid dynamics 3D physico-chemical models regarding the reagent ion and sample gas trajectories and estimate their efficiencies of reagent ion production, reagent ion delivery from the ion source volume into the ion–molecule mixing region, and the interaction between reagent ions and target molecules. The models are validated by laboratory measurements and quantitatively reproduce observed sensitivities to tuning parameters, including ion currents and changes in mass spectra. The study elucidates how the different transport and chemical reactions proceed within the studied inlets, that space charge can already be relevant at ion concentrations of as low as 10⁷ cm⁻³, and compares the two investigated inlet models. The models provide insights into how to operate the inlets and will help in the development of future inlets that further enhance the capability of CIMS.

中文翻译：

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MION2 和 Eisele 型入口中大气压界面化学电离的多物理描述

摘要。化学电离入口是化学电离质谱 (CIMS) 中的基本仪器组件。然而，样气和试剂离子轨迹通常只能以一般和定性的方式理解。在这里，我们使用关于试剂离子和样气轨迹的计算流体动力学 3D 物理化学模型评估两个大气压化学电离入口（MION2 和 Eisele 型入口），并估计它们的试剂离子产生效率、从离子源体积传递试剂离子的效率进入离子-分子混合区域，以及试剂离子和目标分子之间的相互作用。该模型通过实验室测量进行验证，并定量再现观察到的对调谐参数的敏感性，包括离子电流和质谱的变化。该研究阐明了不同的传输和化学反应如何在所研究的入口内进行，空间电荷在低至10 ⁷ cm ^-3的离子浓度下已经相关，并比较了两个研究的入口模型。这些模型提供了有关如何操作入口的见解，并将有助于开发未来的入口，进一步增强 CIMS 的功能。