通过MION Orbitrap装置在线DMA评估10-50nm颗粒的尺寸分辨化学成分
测量尚未生长到几十纳米大小的小气溶胶颗粒的分子组成是困难的，主要是因为颗粒构成的质量很小。同时，早期粒子的成分测量将直接揭示可凝结物种。此外，这些早期颗粒的化学成分控制着气溶胶颗粒的命运，因为它控制着它们对蒸发的鲁棒性。
The vaporization inlet for aerosols (VIA), coupled to an Eisele-type chemical ionisation (NO3-) inlet and a time-of-flight mass spectrometer, has been successfully demonstrated previously (Häkkinen et al 2023, Zhao et al 2023, Zhao et al 2023). Particles from a sample gas are first size selected by a differential mobility analyzer. Trace gases present in the gas phase are stripped by an active charcoal denuder. The particles are then evaporated in a sulfinert-coated stainless steel tube (OD ¼”) at temperatures up to 300 °C. The evaporated molecules are then delivered to a chemical ionization mass spectrometer. The concentration of particles entering the setup are monitored by a scanning mobility particle sizer.
气溶胶的蒸发入口（VIA），与Eisele型化学电离（NO3-）入口和飞行时间质谱仪相耦合，先前已成功证明（Häkkinen等人2023，赵等人2023和赵等人2023）。样品气体中的颗粒首先由微分迁移率分析仪选择尺寸。气相中存在的痕量气体被活性炭剥离器剥离。然后，在高达300°C的温度下，将颗粒在涂有亚硫酸盐的不锈钢管（外径¼”）中蒸发。然后将蒸发的分子输送到化学电离质谱仪。进入装置的颗粒浓度由扫描迁移率粒度仪监测。
Amending the experimental setup of the previous studies by a DMA for size selection before analysis, in this study we investigate how the aerosol composition differs between different particle sizes. Here, particles are first size-selected in a DMA, then vaporized in VIA. The resulting gases are ionized in a MION atmospheric pressure interface chemical ionization inlet using both positively and negatively charged reagent ions and detected in a polarity-switching high-resolution Orbitrap mass spectrometer. We demonstrate the general feasibility of the experimental approach in laboratory measurements using ammonium sulfate and a-pinene derived particles.
在分析之前，通过DMA对先前研究的实验设置进行了修改，以进行尺寸选择，在这项研究中，我们研究了不同粒径的气溶胶成分之间的差异。在这里，颗粒首先在DMA中选择尺寸，然后在VIA中蒸发。产生的气体在MION大气压界面化学电离入口中使用带正负电荷的试剂离子电离，并在极性切换高分辨率Orbitrap质谱仪中检测。我们证明了使用硫酸铵和α-蒎烯衍生颗粒进行实验室测量的实验方法的一般可行性。
In ambient measurements, we show the ability to reach mass closure between the detected concentration of vaporized trace gases even at low particle sizes and low atmospheric particle concentration. We further present first results from a deployment of the novel approach to Mace Head, Ireland, where marine VOC emissions and the composition of 10-20 nm particles were targeted. Coordinated measurements of the gas and particle phase are used to constrain what species contribute to particle formation under the local conditions. The work presents a step towards closing the measurement gap of nano-particle composition and contributes to a more complete understanding of aerosol formation from more complex gas mixtures.
在环境测量中，我们展示了即使在低粒径和低大气颗粒浓度下，检测到的汽化痕量气体浓度之间也能达到质量闭合的能力。我们进一步介绍了在爱尔兰梅斯黑德部署新方法的初步结果，该方法针对的是海洋VOC排放和10-20nm颗粒的成分。气相和颗粒相的协调测量用于限制在局部条件下哪些物种对颗粒形成有贡献。这项工作为缩小纳米粒子成分的测量差距迈出了一步，并有助于更全面地了解更复杂的气体混合物中气溶胶的形成。