Home
Deutsch
Advanced Search
Browse by ...
Publication overview
Contact persons
Help
Publ. Version/Full Text Volltext
 |
|
as soon as is submitted to ZB.
Analysis concepts of aerosols by on-line aerosol mass spectrometry.
Analyse von Aerosolen mittels On-Line Aerosol Lasermassenspektrometrie.
München, Technische Universität, Fakultät Wissenschaftszentrum Weihenstephan, Diss., 2006, 256 S.
It is known that aerosols have an impact on climate, air quality and health. To better characterize these effects, the knowledge of the aerosol particle properties, such as size and chemical composition, at the individual level is needed. Toward this purpose, a Single Particle Aerosol Laser Mass Spectrometer (SPALMS) has been designed and developed to characterize in details the organic fraction of particles. The instrument samples the aerosol with a nozzle system and sizes particles individually by laser velocimetry. The single particle constituents are then volatilized (desorption) and ionized (ionization) by laser. The resulting cations and anions are analyzed with a bipolar time-of-flight mass spectrometer. The resulting mass spectra provide a “fingerprint” of the particle composition. Thus the SPALMS instrument evaluates the mixing state, external versus internal, of the aerosol and allows the investigation of the chemical composition size dependency of the particles. The desorption and ionization steps are critical to obtain a good qualitative chemical analysis of the particle. Indeed many processes take place during these steps which fragment and alter the initial molecules in the particle. The simultaneous desorption and ionization with a single laser (337 nm) combined with a bipolar mass spectrometer is well suited for the analysis of mineral particles. On the other hand, organics in particles are better analyzed by operating first the constituents desorption with an infra-red laser (10.6 micrometers) and then the ionization shortly after with an ultra-violet laser (248 nm). Indeed molecules are softly ionized via a SPI or REMPI process. In this manner the resulting mass spectra are more representative of the particle composition since organics are less fragmented. As the SPALMS instrument involves many different measurement steps based of very different principles, it is equipped with many data acquisition devices (up to 12 channels) to record the corresponding information. By combining these data together, it is possible to improve the reliability of the measurements and to infer additional particle properties such as optical diameter and density.
Um die Wirkungen von Aerosolen auf das Klima, die Luftqualität und die Gesundheit besser charakterisieren zu können, ist es nötig die Eigenschaften der Einzelpartikeln, wie z.B. die Grösse und die chemische Zusammensetzung, besser zu kennen. Aus diesem Grund wurde ein Aerosol-Lasermassenspektrometer (Single Particle Aerosol Laser Mass Spectrometer, SPALMS) zur chemischen Analyse von organischen Verbindungen in Aerosolpartikeln entwickelt. In dem Gerät werden Einzelpartikel zunächst in einem Strahl aerodynamisch fokussiert, dann durch zwei Laser detektiert und anschliessend mittels Lasermassenspektrometrie chemisch analysiert. Durch seinen Aufbau bietet dieses Gerät, im Vergleich zum aktuellen Stand der Technik, die Möglichkeit, verschiedene zusätzliche Informationen über Partikel zu erhalten. Die Vorteile der zweistufigen Desorption und Ionisation der Partikelbestandteile und des verwendeten bipolaren Massenspektrometers zur Identifizierung von Molekülen und zur Bestimmung der Elementspeziation in Partikeln wurden in dieser Arbeit insbesondere demonstriert.
Additional Metrics?
Edit extra informations
Login
Publication type
Other: Thesis
Thesis type
Doctoral thesis
Keywords
Aerosol; laser; mass spectrometry; chemical analysis
Quellenangaben
Pages: 256 S.
University
Technische Universität
University place
München
Faculty
Fakultät Wissenschaftszentrum Weihenstephan
Non-patent literature
Publications