Gas-flow assistance is commonly used in ESI-MS for improved transport and desolvation, and fundamental understanding of the underlying phenomena is essential for improvement of aerodynamic interfaces that couple ESI sources and MS. For this purpose, an electrohydrodynamic model is developed for simulation of charged droplet dynamics under the combined effects of gas flow and electric fields with consideration of space charge interactions within the charged aerosol plume. The model is implemented in COMSOL by exploiting a formalism for establishing the droplet trajectories as a sequence of successive droplets ejected at a frequency defined by the electrospray current. The model is used to assess the effect of two distinct flow configurations and compared to the baseline care of electrospray without assist gas. The simulated flows are jet flows oriented coaxially with the ESI spray, with and without imposed vorticity (swirling). Droplet trajectory simulations of a bimodal droplet population consisting of large primary droplets and small progeny droplets reveal a unique capability for vortical assist jet flow to selectively transmit smaller droplets into the MS due to inertial separation. ESI-MS analysis of fluorinated phosphazines subjected to the different gas flow conditions supports the model predictions. The electrohydrodynamic model developed in this work provides a versatile tool to analyze and design aerodynamic ESI interfaces with rigorous incorporation of drag, inertia, and space-charge repulsion and can be used as a powerful simulation methodology for optimizing charged droplet transmission and ultimately improved analytical performance of gas-assisted ESI-MS workflows.

中文翻译：

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气体辅助电喷雾电离质谱的电流体动力学。


气流辅助通常用于 ESI-MS 中，以改善传输和去溶剂化，而对基本现象的基本了解对于改善耦合 ESI 源和 MS 的空气动力学接口至关重要。为此，开发了电流体动力学模型，用于模拟气流和电场联合作用下的带电液滴动力学，并考虑带电气溶胶羽流内的空间电荷相互作用。该模型在 COMSOL 中实现，利用形式主义将液滴轨迹建立为以电喷雾电流定义的频率喷射的一系列连续液滴。该模型用于评估两种不同流量配置的效果，并与无辅助气体的电喷雾的基线护理进行比较。模拟的流动是与 ESI 喷雾同轴定向的射流，有或没有施加涡流（涡流）。由大的初级液滴和小的子代液滴组成的双峰液滴群的液滴轨迹模拟揭示了涡旋辅助射流由于惯性分离而选择性地将较小的液滴传输到MS中的独特能力。对不同气流条件下氟化磷嗪的 ESI-MS 分析支持了模型预测。这项工作中开发的电流体动力学模型提供了一种通用工具来分析和设计空气动力学 ESI 接口，严格结合阻力、惯性和空间电荷排斥力，可用作优化带电液滴传输并最终提高分析性能的强大模拟方法。气体辅助 ESI-MS 工作流程。