| since 01/2012
05/2011 - 11/2011
10/2006 - 05/2011
| PhD student
diploma thesis in Prof. Dr. Thorsten Hoffmann´s group at
the JGU Mainz
untergraduate studies in chemistry at the WWU Muenster
Abitur in Schmallenberg
Building 2.224 / Room 03-110
Tel.: +49 6131 – 39 26663
Fax: +49 6131 – 39 25336
Development of a plasma-based ion source for the on- and offline analysis of secondary organic aerosols
Secondary organic aerosol (SOA) is formed when oxidation products of volatile organic compounds (VOCs) undergo gas-to-particle conversions. It accounts for a substantial fraction of ambient tropospheric aerosol and has implications on the earth’s climate and human health. To gain detailed knowledge about the formation, properties and transformations of SOA, much research has been done over the last few decades and many sophisticated techniques have been developed to resolve the chemical composition of SOA. However, none of these measurement techniques allows a complete chemical analysis of SOA particles and, despite much excellent work on themes such as identifying biogenic and anthropogenic SOA precursors, the knowledge about formation mechanisms, properties and evolution of SOA often remains uncertain. Yet, without this knowledge it is impossible to predict and evaluate the implications of SOA on atmospheric processes, climate and human health.
Today the Aerosol Mass Spectrometer (AMS) is probably the most common technique to obtain chemical and size-resolved information about sub-micron aerosol particles. However, it uses an electron impact ion source, which is a hard ionization technique and leads to many fragmentations. Therefore, it is not possible to monitor single organic compounds, which can serve as marker compounds for anthropogenic activities, wild fires or natural atmospheric conditions.
Addressing these technical drawbacks of the AMS and further questions concerning the chemical composition of SOA, we are developing a new, versatile ion source for the on- and offline analysis of SOA particles. The ion source is based on a low-temperature Helium plasma at atmospheric pressure, which is induced through glow discharges or dielectric barrier discharges. In such a plasma ion source, excited Helium atoms can ionize analyte molecules through the so-called Penning Ionization. This very soft chemi-ionization offers the possibility to obtain mass spectra with very little fragmentation. Additionally, the ion source can operate already at relatively low temperatures of 30 to 100 °C, depending on the kind of chosen discharge. This means lower temperatures during the ionization process, and thus the possibility to measure even very thermolabile substances in SOA particles without fragmentations.
secondary organic aerosols (SOA), ion sources, low-temperature plasmas (glow discharge, dielectric barrier discharge), ambient mass spectrometry, instrumentation