Abstract

Numerous methods have been developed to analyze particulate matter in ambient aerosols. Typically, particle composition is measured by removing the particles from the gas by filtration or impaction and transporting the sample to a laboratory where “off-line” analysis is performed with either bulk or single particle analytical techniques. There are a several difficulties with these methods. First, the sample is collected over an extended period of time, so short term temporal variations in the composition cannot be resolved. Second, compounds may condense on or evaporate from the impactor surface or filter over the course of sampling, altering their composition. Third, the turnaround time between sampling and analysis is slow. For these reasons, off-line analysis based upon filtration or impaction cannot be easily adapted to real-time sampling and analysis and they may not give analytical results that are representative of the true composition. These problems can be overcome with on-line methods of analysis.

© 1994 Optical Society of America