| PhD student at JGU Mainz
Diploma thesis at JGU Mainz (AK Hoffmann)
Diploma study (chemistry) at JGU Mainz
Civilian service at AWO Seniorenzentrum Wörrstadt
Abitur in Nieder-Olm
Building 2224 / Room 03-110
Tel.: +49 6131 39-25877
Fax.: +49 6131 39-25336
Quantification and characterization of reactive α-dicarbonyl compounds in atmospheric aerosols
Atmospheric aerosols influence climate, air quality, and human health. Particles with aerodynamic diameters of less than one micrometer are of special interest, since they exhibit the longest residence time in the atmosphere. These particles comprise a large fraction of secondary organic material. Traditional models predicting formation and growth of secondary organic aerosols (SOA) are based on the gas-to-particle partitioning of low volatility products from the atmospheric oxidation of volatile organic compounds (VOCs). However, large discrepancies have been observed between modeled and measured SOA mass. Recently, heterogeneous reactions and reactions in the particle phase have been proposed to play an important role in formation and transformation processes of SOA. Reactive α-dicarbonyl compounds (glyoxal and methylglyoxal) are currently used as model compounds for investigations on the mechanisms and impacts of such reactions.
A selective and robust method for the determination of glyoxal and methylglyoxal at ultra-trace levels was developed and validated to assess the contribution of these compounds to SOA mass. The method is based on the extraction of aerosols sampled on fluorocarbon coated borosilicate filters and their subsequent derivatization using 2,4-dinitrophenylhydrazin. Therefore, highly selective measurements using HPLC-DAD-ESI-MS/MS were enabled. The method allowed analysis of glyoxal, methylglyoxal, as well as their reversibly formed higher molecular weight compounds (hydrates, acetal oligomers). Low limits of detection were achieved deploying a newly developed purification method for the derivatization reagent, which otherwise contained high background values of the analytes. All method parameters were carefully evaluated and the applicability of the method for measurements of ambient aerosols was demonstrated in terms of comparison to a standard addition method on ambient samples. Applications of the method in field and laboratory campaigns allowed investigations on relevance of α-dicarbonyl compounds for SOA, potential correlations with anthropogenic trace gases, aging of SOA, and mechanisms of gas-to-particle partitioning of glyoxal.
Additionally, the formation of light-absorbing material in aqueous aerosol mimics containing glyoxal was investigated using HPLC-DAD-ESI-MS/MS. A bicyclic imidazole was identified to be a major contributor to the observed absorbance features through the analysis of synthesized reference compounds. However, the production rate of this compound was two orders of magnitude lower than those of the main reaction products. This demonstrated the necessity of molecular identification of trace-compounds for the assessment of optical properties of ambient aerosols.
Secondary organic aerosols (SOA), α-dicarbonyl compounds, aging of SOA, High-Performance-Liquid-Chromatography (HPLC), UV-Vis Spectrophotometry, Ion Trap-Mass-Spectrometry (IT/MS), Electrospray-Ionization (ESI), Atmospheric-Pressure-Chemical-Ionization (APCI), method development, method optimization, ultra-trace analysis of organic compounds in complex matrices