Probing surfaces of atmospherically relevant organic particles by easy ambient sonic-spray ionization mass spectrometry (EASI-MS)
Probing surfaces of atmospherically relevant organic particles by easy ambient sonic-spray ionization mass spectrometry (EASI-MS)
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DOI：
10.1039/c8sc03851a
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发表时间：
2019-01-21
期刊：
影响因子：
8.4
通讯作者：
Finlayson-Pitts, B. J.
中科院分区：
文献类型：
--
作者：
Wingen, L. M.;Finlayson-Pitts, B. J.
环境和实验室产生的颗粒都可以具有与本体不同的表面组成，但目前很少有分析技术可用于探测这些差异。简单的环境声喷雾电离质谱法（EASI-MS）适用于固体，实验室产生的颗粒与核-壳形态形成的各种二羧酸。软电离促进了两种化合物的母峰检测，由此可以从相对信号强度确定探测的深度。两种不同配置的定制雾化器的报告，产生不同的探头深度。在“正交模式”中，雾化器与颗粒流相距约10厘米并且与MS入口成90度角，雾化器液滴的蒸发在与颗粒相互作用之前形成离子。正交模式EASI-MS的探针深度在这些粒子系统中显示为2-4 nm。在“液滴模式”中，雾化器和颗粒流彼此靠近并且靠近MS入口，使得颗粒与带电液滴相互作用。这种配置导致颗粒完全溶解，并得到与过滤器收集和颗粒提取（散装）相似的颗粒组成。这些研究表明，EASI-MS是一种很有前途的技术，用于探测不均匀的空气中有机颗粒的化学结构。
Both ambient and laboratory-generated particles can have a surface composition different from the bulk, but there are currently few analytical techniques available to probe these differences. Easy ambient sonic-spray ionization mass spectrometry (EASI-MS) was applied to solid, laboratory-generated particles with core-shell morphologies formed from a variety of dicarboxylic acids. The soft ionization facilitated parent peak detection for the two compounds, from which the depth probed could be determined from the relative signal intensities. Two different configurations of a custom-made nebulizer are reported that yield different probe depths. In the "orthogonal mode," with the nebulizer similar to 10 centimeters away from the particle stream and at a 90 degrees angle to the MS inlet, evaporation of the nebulizer droplets forms ions before interaction with the particles. The probe depth for orthogonal mode EASI-MS is shown to be 2-4 nm in these particle systems. In the "droplet mode", the nebulizer and particle streams are in close proximity to each other and the MS inlet so that the particles interact with charged liquid droplets. This configuration resulted in full dissolution of the particles and gives particle composition similar to that from collection on filters and extraction of the particles (bulk). These studies establish that EASI-MS is a promising technique for probing the chemical structures of inhomogeneous airborne organic particles.