Quantification of Imidazole Compounds in Ambient Aerosols at Suburban and Forest Sites in Western Japan

Ambient aerosol particles at forest and suburban sites in western Japan were analyzed for imidazole compounds, such as 4 (5)-Methylimidazole (4-MI), 1-ethylimidazole (1-EI), 2-ethylimidazole (2-EI), and imidazole-2-carboxaldehyde (IC). The aerosols were collected on quartz fiber filters and extracted by the solid phase extraction method. The extract was analyzed by HPLC/Q-TOF-MS using an ion-pairing agent. The concentration of 4-MI in winter was higher than those in summer at the forest site; its concentration was highest among the analyzed imidazoles. The concentration of 4-MI in the suburban site was several times higher than the forest site. Anthropogenic activities, such as vehicle emissions, are considered to be the major source of 4-MI in this region.