Chemical and physical characterization of transported evolving aerosols in an in vitro system is complex. The challenges include appropriate sampling sensitivity, measurement capabilities, and performing online measurements of constituents in the flowing aerosol during exposure. We assessed the performance of single-photon ionization mass spectrometry in measuring aerosol properties within an in vitro aerosol exposure system. The sampling efficiency of the instrument was studied under three protocols to capture the evolving aerosol process inside the exposure system, and it was evaluated using computational fluid dynamics modeling. The changes in the aerosol as dilution is applied show not only a reduction in concentration of the traced substances but also selective sampling due to evolution of the aerosol and (gas/liquid) phase partitioning of the substances forming the aerosol or a change in the aerosol properties. These effects have potentially a direct impact on the delivered dose, as aerosol deposition is dependent on particle size. Dilution affects the chemical concentration of the substances as well as the interconnected physical properties of the aerosol; therefore, the experimental design of in vitro studies should not only report the dilution flow rates but also details of the applied dilution protocol. This adds a layer of complexity to the design and comparison of studies. We also discuss the potential and limitations of single-photon ionization mass spectrometry as a tool in in vitro monitoring of aerosols.

中文翻译：

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在线监测体外气溶胶暴露实验的单光子电离质谱评估。

在体外系统中运输的不断发展的气溶胶的化学和物理表征是复杂的。挑战包括适当的采样灵敏度，测量能力以及在暴露过程中对流动的气溶胶中的成分进行在线测量。我们评估了单光子电离质谱法在体外气溶胶暴露系统中测量气溶胶特性的性能。根据三种协议对仪器的采样效率进行了研究，以捕获暴露系统内部不断发展的气溶胶过程，并使用计算流体动力学模型对其进行了评估。进行稀释时，气溶胶的变化不仅显示出痕量物质的浓度降低，而且由于气溶胶的演变和形成气溶胶的物质的（气相/液相）分配或气溶胶的变化而导致的选择性采样属性。这些影响可能直接影响所输送的剂量，因为气溶胶沉积取决于粒径。稀释会影响物质的化学浓度以及气溶胶的相互关联的物理特性；因此，体外研究的实验设计不仅应报告稀释流速，而且应详细说明所应用的稀释方案。这为研究的设计和比较增加了一层复杂性。