Real time in situ chemical characterization of sub-micron organic aerosols using Direct Analysis in Real Time mass spectrometry (DART-MS): the effect of aerosol size and volatility
Real time in situ chemical characterization of sub-micron organic aerosols using Direct Analysis in Real Time mass spectrometry (DART-MS): the effect of aerosol size and volatility
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DOI：
10.1039/c3an00168g
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发表时间：
2013-01-01
期刊：
影响因子：
4.2
通讯作者：
Wilson, Kevin R.
中科院分区：
文献类型：
--
作者：
Chan, Man Nin;Nah, Theodora;Wilson, Kevin R.
真实的时间直接分析（DART）质谱是一种适用于有机气溶胶的原位化学分析的大气压电离技术。在这里，通过将纳米尺寸的气溶胶流引入电离区来获得质谱，电离区是离子源和质谱仪的大气入口之间的开放空间。模型单组分气溶胶被用来显示如何气溶胶的大小和挥发性影响测量的离子信号在不同的DART气体温度。结果表明，对于等效的气溶胶质量浓度，离子信号与颗粒表面积成比例，较小直径的油酸气溶胶产生较高的离子信号相对于较大直径的气溶胶。对于相同尺寸但不同蒸气压的气溶胶，对于更挥发性的琥珀酸气溶胶的离子信号比更不挥发性的己二酸和辛二酸颗粒大。从测量的变化，气溶胶的大小，产生的DART源，这些模型气溶胶的径向探测深度范围从1到10纳米，其幅度取决于气溶胶的物理化学性质和DART气体温度。气溶胶蒸发模型表明，离子信号与气溶胶尺寸的变化相关，并取决于蒸发的气溶胶质量的总量，与其中气相分子首先从气溶胶表面解吸电离之前的机制一致。这项工作的结果作为一个基础，为未来的调查的质谱，电离途径，探测深度的气溶胶使用DART。
Direct Analysis in Real Time (DART) mass spectrometry is an atmospheric pressure ionization technique suitable for in situ chemical analysis of organic aerosols. Here, mass spectra are obtained by introducing a stream of nanometer-sized aerosols into the ionization region, which is an open space between the ion source and the atmospheric inlet of mass spectrometer. Model single component aerosols are used to show how the aerosol size and volatility influence the measured ion signals at different DART gas temperatures. The results show that for equivalent aerosol mass concentrations, the ion signal scales with particle surface area, with smaller diameter oleic acid aerosols yielding higher ion signals relative to larger diameter aerosols. For the aerosols of the same size, but different vapor pressures, the ion signal is larger for more volatile succinic acid aerosols than less volatile adipic and suberic acid particles. From the measured changes in aerosol size, produced by the DART source, the radial probing depth for these model aerosols range from 1 to 10 nm, the magnitude of which depends upon the physiochemical properties of the aerosols and DART gas temperature. An aerosol evaporation model reveals that the ion signal is correlated with changes in aerosol size and depends upon the total quantity of evaporated aerosol mass, consistent with a mechanism in which gas-phase molecules are first desorbed from the aerosol surface prior to ionization. The results of this work serve as a basis for future investigations of the mass spectra, ionization pathways, and probing depth of the aerosols using DART.