Real Time in Situ Chemical Characterization of Submicrometer Organic Particles Using Direct Analysis in Real Time-Mass Spectrometry
Real Time in Situ Chemical Characterization of Submicrometer Organic Particles Using Direct Analysis in Real Time-Mass Spectrometry
复制标题
DOI：
10.1021/ac302560c
复制
发表时间：
2013-02-19
影响因子：
7.4
通讯作者：
Wilson, Kevin R.
中科院分区：
文献类型：
--
作者：
Nah, Theodora;Chan, ManNin;Wilson, Kevin R.
实时质谱直接分析（DART-MS）用于在大气压下实时分析纳米级有机气溶胶颗粒的表面化学成分。通过在 DART 电离源和质谱仪的大气压入口之间引入粒子流，气溶胶暴露于含有部分亚稳态氦原子或氮分子的氦气或氮气热流中。在这种配置中，有机颗粒的分子成分被解吸、电离，并以减少的分子离子碎片进行检测，从而可以进行成分识别。检测到的气溶胶颗粒包括烷烃、烯烃、酸、酯、醇、醛和氨基酸。 DART-MS 产生的离子信号与气溶胶表面积而不是体积成比例，这表明 DART-MS 是测量颗粒界面化学成分的可行技术。对于油酸，离开电离区域的气溶胶流的粒径测量表明，探测深度取决于解吸温度，并且在 500 摄氏度的 DART 加热器温度（使用氮气作为 DART 气体）下，对于 185 nm 直径的颗粒，探测深度估计约为 5 nm。测量臭氧与亚微米油酸颗粒的反应，以证明该技术在非均相反应中识别产物和量化反应速率的能力。
Direct analysis in real time mass spectrometry (DART-MS) is used to analyze the surface chemical composition of nanometer-sized organic aerosol particles in real time at atmospheric pressure. By introducing a stream of particles in between the DART ionization source and the atmospheric pressure inlet of the mass spectrometer, the aerosol is exposed to a thermal flow of helium or nitrogen gas containing some fraction of metastable helium atoms or nitrogen molecules. In this configuration, the molecular constituents of organic particles are desorbed, ionized, and detected with reduced molecular ion fragmentation, allowing for compositional identification. Aerosol particles detected include alkanes, alkenes, acids, esters, alcohols, aldehydes, and amino acids. The ion signal produced by DART-MS scales with the aerosol surface area rather than volume, suggesting that DART-MS is a viable technique to measure the chemical composition of the particle interface. For oleic acid, particle size measurements of the aerosol stream exiting the ionization region suggest that the probing depth depends upon the desorption temperature, and the probing depth is estimated to be on the order of 5 nm for a 185 nm diameter particle at a DART heater temperature of 500 degrees C with nitrogen as the DART gas. The reaction of ozone with submicrometer oleic acid particles is measured to demonstrate the ability of this technique to identify products and quantify reaction rates in a heterogeneous reaction.