Characterization of 2-methylglyceric acid oligomers in secondary organic aerosol formed from the photooxidation of isoprene using trimethylsilylation and gas chromatography/ion trap mass spectrometry.
In the present work, we have characterized in detail the chemical structures of secondary organic aerosol (SOA) components that were generated in a smog chamber and result from the photooxidation of isoprene under high-NO(x) conditions typical for a polluted atmosphere. Isoprene high-NO(x) SOA contains 2-methylglyceric acid (2-MG) and oligoester derivatives thereof. Trimethylsilylation, in combination with capillary gas chromatography (GC)/ion trap mass spectrometry (MS) and detailed interpretation of the MS data, allowed structural characterization the polar oxygenated compounds present in isoprene SOA up to 2-MG trimers. GC separation was achieved between 2-MG linear and branched dimers or trimers, as well as between the 2-MG linear dimer and isomeric mono-acetate derivatives thereof. The electron ionization (EI) spectra of the trimethylsilyl derivatives contain a wealth of structural information, including information about the molecular weight (MW), oligoester linkages, terminal carboxylic and hydroxymethyl groups, and esterification sites. Only part of this information can be achieved with a soft ionization technique such as electrospray (ESI) in combination with collision-induced dissociation (CID). The methane chemical ionization (CI) data were used to obtain supporting MW information. Interesting EI spectral differences were observed between the trimethylsilyl derivatives of 2-MG linear and branched dimers or trimers and between 2-MG linear dimer mono-acetate isomers.
Szmigielski
Rafal
R
Department of Pharmaceutical Sciences, University of Antwerp (Campus Drie Eiken), Universiteitsplein 1, BE-2610 Antwerp, Belgium.
Surratt
Jason D
JD
Vermeylen
Reinhilde
R
Szmigielska
Katarzyna
K
Kroll
Jesse H
JH
Ng
Nga L
NL
Murphy
Shane M
SM
Sorooshian
Armin
A
Seinfeld
John H
JH
Claeys
Magda
M
D000336:Aerosols; D000393:Air Pollutants / Q000737:chemistry*; D000397:Air Pollution; D002070:Butadienes / Q000737:chemistry* / Q000528:radiation effects; D019281:Dimerization; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D005971:Glutamates / Q000737:chemistry*; D045782:Hemiterpenes / Q000737:chemistry* / Q000528:radiation effects; D007536:Isomerism; D008027:Light; D010084:Oxidation-Reduction; D010420:Pentanes / Q000737:chemistry* / Q000528:radiation effects; D014297:Trimethylsilyl Compounds / Q000737:chemistry*
D000336:Aerosols; D000393:Air Pollutants; D002070:Butadienes; D005971:Glutamates; D045782:Hemiterpenes; D010420:Pentanes; D014297:Trimethylsilyl Compounds; C005059:isoprene; C025648:2-methylglutamic acid