Thermal Desorption-Multiphoton Ionization Time-of-Flight Mass Spectrometry of Individual Aerosol Particles: A Simplified Approach for Online Single-Particle Analysis of Polycyclic Aromatic Hydrocarbons and Their Derivatives
Thermal Desorption-Multiphoton Ionization Time-of-Flight Mass Spectrometry of Individual Aerosol Particles: A Simplified Approach for Online Single-Particle Analysis of Polycyclic Aromatic Hydrocarbons and Their Derivatives
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DOI：
10.1021/ac802296f
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发表时间：
2009-04-01
影响因子：
7.4
通讯作者：
Zimmermann, Ralf
中科院分区：
文献类型：
--
作者：
Bente, Matthias;Sklorz, Martin;Zimmermann, Ralf
在线单粒子（SP）激光质谱（MS）是基础和应用气溶胶研究的重要工具。通常，激光解吸/电离（LDI）用于从纳米或微米尺寸的空气传播颗粒中烧蚀和电离原子和分子碎片，并且飞行时间分析仪（TOFMS）用于主要无机分析物的质量选择性检测。分子有机化合物的检测仅在非常特殊的实验条件下才有可能，并且非常依赖于颗粒基质，因此仅限于特殊应用。最近的研究表明，通过两步激光解吸（LD）共振增强多光子电离（REMPI）定位方法的实施，可以记录多环芳烃（PAH）及其衍生物的单颗粒分子特征（LD-REMPI-SP-TOFMS）。通过这一点，来自不同来源的颗粒物可以区分通过特定的分子源示踪剂，如软木燃烧的retene或汽油车排放的指示剂较大的PAH的模式。然而，LD-REMPI-SP-TOFMS方法的一个缺点-特别是对于现场应用-是必须操作和调节两个激光器。本文介绍了单粒子质谱中热解吸步骤的成功实现（TD-REMPI-SP-TOFMS）。在通过颗粒速度测定法确定尺寸之后，在TOFMS的离子源中的加热表面上热解吸单个颗粒。解吸的分子随后通过REMPI电离，其选择性地解决PAH和分子痕量指示剂。TD-REMPI-SP-TOFMS概念是用参考粒子测试的，并应用于汽车尾气和环境监测。与双激光方法（LD-REMPI-SP-TOFMS）获得的结果的比较表明，这里提出的专利TD-REMPI-SP-TOFMS技术几乎同样适用于研究环境气溶胶和气溶胶排放中的有机源示踪剂。然而，新方法的耐用性和简单性的增加可能有利于其在气溶胶科学和技术领域的应用。
Online single-particle (SP) laser mass spectrometry (MS) is an important tool for fundamental and applied aerosol research. Usually laser desorption/ionization (LDI) is applied for ablation and ionization of atoms and molecular fragments from the nanometer- or micrometer sized air-borne particles and time-of-flight analysers (TOFMS) are used for mass-selective detection of mainly inorganic analytes. The detection of molecular organic compounds is solely possible under very special experimental conditions and extremely dependent on the particle matrix and thus limited to special applications. Very recently it was shown that by implementation of a two-step laser desorption (LD) resonance-enhanced multiphoton ionization (REMPI) postionization approach the single-particulate molecular signature of polycyclic aromatic hydrocarbons (PAH) and their derivatives can be recorded (LD-REMPI-SP-TOFMS). By this, particles from different sources could be differentiated via the patterns of s pecific molecular source tracers such as retene for soft wood combustion or larger PAH as indicator for gasoline car emissions. One drawback of the LD-REMPI-SP-TOFMS method-in particular for field applications-is, however, the necessity of operation and adjustment of two lasers. In this paper the successful implementation of a thermal desorption step in single-particle mass spectrometry is described (TD-REMPI-SP-TOFMS). After size determination by particle velocimetry, individual particles are thermally desorbed on a heated surface in the ion source of the TOFMS. Desorbed molecules are ionized subsequently by REMPI, which addresses selectively PAH and molecular trace indicators. The TD-REMPI-SP-TOFMS concept Is tested with reference particles and applied for automotive exhaust and ambient monitoring. The comparison of the results with the ones obtained by the two-laser approach (LD-REMPI-SP-TOFMS) indicates that the patented TD-REMPI-SP-TOFMS technology presented here is nearly equally well suited for studying organic source tracers in ambient aerosols and aerosol emissions. The increased ruggedness and simplicity of the new approach, however, may favor its application for field measurements in aerosol science and technology.