A condensation-growth and impaction method for rapid off-line chemical-characterization of organic submicrometer atmospheric aerosol particles

Abstract

An off-line method for rapid analysis of submicrometer organic atmospheric aerosol particles was developed. The method first uses condensational growth of submicrometer particles and then impaction to collect the particles for off-line chemical analysis. This condensation-growth and impaction system (C-GIS) converts the aerosol into a hydrosol that can be readily drawn into a variety of systems for chemical analysis. The analytical instrument we used to test the C-GIS was a capillary electrophoresis system that uses either indirect UV-detection or mass spectrometric detection. In this paper we show results for non-size segregated, off-line analysis of real atmospheric particles ( <1.5 μm ). The chemical composition was determined from atmospheric aerosol samples collected with sampling times of 10 min . If size-segregated measurements are desired, the C-GIS can be coupled to a differential mobility analyzer (DMA) to permit size-classification upstream of the C-GIS. The feasibility of using the C-GIS for making rapid chemical characterization of size-segregated submicrometer aerosol particles was evaluated by using the system to condition and collect laboratory-generated model organic aerosol particles and subsequent analysis. The results indicate that the C-GIS can be used for size-segregated particle sampling with subsequent off-line chemical particle analysis with a sampling time of at least 20 min under typical atmospheric conditions. For atmospheric applications, however, its capability to rapidly measure size-segregated chemical composition is limited by the particle concentration present downstream of the DMA, and therefore, such measurements typically can only be made in heavily polluted areas or within the scope of source-characterization studies.