STTR Phase II: Aerosol Mass Spectrometer for Size and Composition Analysis of Sub-Micron Particles

这一小型企业技术转让第二阶段项目将开发一种气溶胶采样仪，可实时提供亚微米级颗粒物的尺寸和化学成分信息。该仪器将应用于目前无法获得商业仪器的空气颗粒物分析。该设备将成熟的气溶胶采样和粒度分离技术与独特的热线颗粒汽化/质谱学检测方案相结合。与目前使用高功率激光进行颗粒汽化的研究系统相比，该仪器的复杂性较低，因此将显著降低颗粒分析的成本。该粒子质谱仪结合了空气动力气溶胶采样、进样和充电系统，产生一束带电粒子束，其大小由其与电场的相互作用决定。被选择的质量束撞击着一根热线，粒子在那里蒸发和电离。生成的离子用分子飞行时间(TOP)质谱仪进行分析。第一阶段的工作成功地将粒子质谱仪与热线蒸发技术相结合，使用了四极质谱检测技术。最初的工作已经证明了对直径为0.11 mm的液体和固体盐颗粒的单个颗粒的化学成分检测。检测下限将在二期工程中扩大到-0.03 1lm直径。该仪器将用于基本的大气气溶胶研究，并作为对燃烧源(燃煤发电厂、商用飞机和汽车尾气)颗粒物排放的在线实时监测。

This Small Business Technology Transfer Phase II project will develop an aerosol sampling instrument that yields both size and chemical composition information in real time for sub-micron sized particles. The instrument will have application to airborne particle analysis where commercial instrumentation is currently unavailable. The device combines proven technology for aerosol sampling and size separation with a unique hot wire particle vaporization/mass spectrometric detection scheme. This instrument is less complex compared to current research systems utilizing high power lasers for particle vaporization and, hence, will provide a significant cost reduction for particle analysis. The particle mass spectrometer combines an aerodynamic aerosol sampling inlet and charging system which generates a beam of charged particles whose size is determined by its interaction with electric fields. The mass selected beam impacts a hot wire where the particles vaporize and ionize. The resulting ions are analyzed with a molecular time of flight (TOP) mass spectrometer. The Phase I work has successfully coupled the particle mass spectrometer with the hot wire vaporization technique using quadrupole mass spectrometric detection. The initial work has demonstrated chemical composition detection for single particles for a range of liquid and solid salt particles down to 0.1 1lm diameter. The detection limit will be extended in the Phase II work to -0.03 1lm diameter. The instrument will be useful for basic atmospheric aerosol research and as a real time monitor for on-line particulate emissions from combustion sources (coal-fired power plants, and exhaust from commercial aircraft and automobiles).