10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Charge Distribution Characterization of an Indirect Ionization Soft X-ray Operated under Various Test Gas Environments
SIQIN HE, Derek Oberreit, Kanomax FMT, Inc.
Abstract Number: 1601 Working Group: Instrumentation
Abstract Based on measuring mass (m) to charge (z) ratio of samples, mass spectrometry (MS) techniques have their analysis performance rely on reliable and steady ionization methods. The Chemical Ionization (CI) technique, as one of them, has been favorably used to study organic species in gaseous and particle phases because of its gentle ionization, reduced fragmentation, and flexible ion polarity selection during the ionization process. The operation of CIMS requires a bipolar ion source to generate positive or negative reagent ions, where the radioactive ion sources Am241 and Po210 have been commonly used in virtue of their simple operation and steady charge distribution, which meanwhile also limits the use of CIMS in field due to the safety regulations over radioactive sources. To facilitate the application of mass spectrometry analysis technique in field measurements, new ionizers have been developed based on soft x-ray ionization as an alternative source for such aerosol particle measurements that require bipolar charge conditioning, and its potential to be utilized in different operation environments is of great interest.
The ionization performance has been proven to be significantly influenced by the charging environment, e.g. the polarizability and properties of ionizing gas, the moisture level, and the chemical vapor content. In this study, the indirect ionization soft x-ray charge conditioner was evaluated by investigating its charge distribution when ionizing H2O or amine molecules in various test gases, including clean dry air (CDA), high-purity nitrogen (N2), high-purity carbon dioxide (CO2), and Argon (Ar). In addition, the transporting tubing material has also been reported to have an effect on charge conditioning performance, so a measurement comparing charge distribution of this soft x-ray charge conditioner with or without silicone tubing was also conducted and reported.