The aerosol samples were colleted from 3 different Chinese cities during different seasons with a novel cascade impactor developed by Tsinghua University. The impactor has 7 stages to separate the aerosols according to their air dynamics diameters. A flat, ideally uniform deposition of the sample on rotatable substrate plates allows the use of multiple analytical techniques. Three other typical contamination samples were collected from Chinese space environment simulation systems on ground. The chemical composition is always complicated and the total amount of the sample quantity is often limited, which causes the common difficulties for analysis. The characterization can offer the scientific evidence to figure out the contamination sources as well as the way to resolve the contamination problems.
The multiple analysis techniques used include SEM-EDS, GC & GC/MS as well as time¨Cof-flight secondary ion mass spectrometry (TOF-SIMS). Possible information of the above samples has been deduced from the experimental results. It is tried to deduce some possible inorganic information of the compounds from the quantitative elemental information by SEM-EDS, due to that most aerosols are consisted of compounds, but not elements. In order to get the organic information by GC or GC/MS from the samples with limited amount, the extraction efficiencies have been improved greatly. The feasibility of applying the state-of-the-art TOF-SIMS to characterization of the above samples is tentatively discussed with some preliminary results. Various advantages of TOF-SIMS over the existing conventional techniques include its unique fingerprint identification ability to detect all kinds of elements, isotopes as well as compounds due to its ultrahigh mass resolution. In addition, some hidden information, including different contaminants and its formation history, can be deduced with secondary ion images. Combining the preliminary results of TOF-SIMS depth profiling with secondary ion image, the 3D composition distribution is possible to be deduced.
It is important to integrate the information deduced by the above multiple analysis techniques in order to understand the contamination well. The experimental and discussion will be presented in this paper. |