Adsorption of Gaseous Organic Compounds onto PM2.5 During Air Sampling

Abstract

For the quantitative determination of organic compounds in particulate matter less than 2.5 μm (PM2.5), it is first collected on a filter paper using a high-volume air sampler and the organic compounds are eluted with an organic solvent. However, a positive error occurs in the quantitative results owing to the adsorption of gaseous organic compounds onto the filter paper and PM2.5. This study investigates the adsorption of gaseous organic compounds onto PM2.5. The adsorption of these compounds was evaluated by air sampling using two filter papers: one on which the target organic compounds were spiked (upstream filter) and another on which PM2.5 was adsorbed (downstream filter). Results obtained using n-alkanes clearly indicated a large amount of gaseous n-C₂₆ adsorption onto PM2.5. In contrast, octadecyl benzene, which has a boiling point similar to that of n-C₂₆H₅₄, did not show specific adsorption onto PM2.5. These results suggested that the adsorption of gaseous organic compounds onto PM2.5 may be affected by the volatility and chemical structure of the organic compound. Furthermore, in the component analysis of organic compounds in PM2.5, a large positive error may occur for a specific organic compound with low volatility due to its gas adsorption onto PM2.5.