Identification and characterization of aging products in the glyoxal/ammonium sulfate system – implications for light-absorbing material in atmospheric aerosols Institute for Inorganic and Analytical Chemistry, Johannes Gutenberg-University Mainz, 55128 Mainz, Germany
23 Jul 2012
Received: 07 February 2012 – Published in Atmos. Chem. Phys. Discuss.: 29 February 2012 Abstract. In this study we report the identification of bicyclic imidazoles in aqueous
aerosol mimics using HPLC-ESI-MS/MS. 2,2'-Biimidazole was identified to be a
major contributor to the 280 nm absorbance band observed in mixtures of
glyoxal and ammonium sulfate, despite the fact that its production rate is
two orders of magnitude lower than the previously reported production rates
of imidazole or imidazole-2-carboxaldehyde. The molar absorptivity of
2,2'-biimidazole was determined to be (36 690 ± 998) M−1 cm−1.
This demonstrates the necessity of molecular product identification at trace
levels to enable a better understanding of relevant absorbing species.
Additionally, the formation of lower polarity products including formamides
of imidazoles is proposed. The role of imidazoles and other light-absorbing
species in the formation of SOA and optical properties of SOA is discussed
and potentially interesting fields for future investigations are outlined.
Revised: 13 July 2012 – Accepted: 16 July 2012 – Published: 23 July 2012
Citation: Kampf, C. J., Jakob, R., and Hoffmann, T.: Identification and characterization of aging products in the glyoxal/ammonium sulfate system – implications for light-absorbing material in atmospheric aerosols, Atmos. Chem. Phys., 12, 6323-6333, doi:10.5194/acp-12-6323-2012, 2012.