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| Titel |
Characterization of Polyfunctional Oligomers From Pyruvic Acid Photolysis in Water |
| VerfasserIn |
M. R. Hoffmann, A. G. Rincon, A. J. Colussi |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029031
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| Zusammenfassung |
| Humic substances (HUMICS) are widespread in natural surface waters, where they ultimately
undergo solar photolysis into small alpha-dicarbonylic species, such as glyoxal, glyoxylic and
pyruvic acids. Humic-like substances (HULIS) are also found in the atmospheric
aerosol. We report a laboratory study of the photolysis of aqueous pyruvic acid
(PA), solutions at concentrations representative of the atmospheric aerosol using
UV-absorption, high resolution electrospray mass (EMS), and nuclear magnetic
resonance (NMR) spectrometries. PA yields polyfunctional oligomers reaching
molecular masses of up to 900 Da, some of which absorb into the visible. Exact mass
determinations (to the fourth decimal place) yielded unique molecular formulae
in most cases, which were confirmed by collisionally induced dissociation (CID)
patterns and the analysis of the products of photolysis of [2-13C] and [3-13C] PA
isotopologues. The lowest energy CID channels corresponded to neutral fragment losses of
masses: 18 (H2O), 44 (CO2), 46 (HCOOH) and 62 (CO3H2. 13C- and 1H- NMR of
[2-13C] and [3-13C] PA photolysis mixtures revealed the presence of various carbonyl
functionalities (190 to 230 ppm) displaying 2J(CC) and 3J(CC) couplings among
themselves and with anomeric carbons (~ 96 ppm). Based on this evidence, we
propose molecular structures and a mechanism of formation for these oligomers.. |
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