Mimicking the atmospheric OH-radical-mediated photooxidation of isoprene: formation of cloud-condensation nuclei polyols monitored by electrospray ionization mass spectrometry.
Recently, it has been proposed (M. Claeys et al., Science 2004; 303: 1173) that the atmospheric OH-radical-mediated photooxidation of isoprene is a source of two major secondary organic aerosol (SOA) components, that is, 2-methylthreitol and 2-methylerythritol. These diastereoisomeric tetrols, which were characterized for the first time in the fine size fraction (<2.5 microm aerodynamic diameter) of aerosols collected in the Amazon rain forest during the wet season, were proposed to enhance the capability of the aerosols to act as cloud-condensation nuclei. In the present study, we performed the oxidation of isoprene in aqueous solution under conditions that attempted to mimic atmospheric OH-radical-induced photooxidization, and monitored and characterized on-line the reaction products via electrospray ionization mass (and tandem mass) spectrometry in the negative ion mode. The results show that the reaction of isoprene with photo- or chemically generated hydroxyl radicals indeed yields 2-methyltetrols. Other polyols were also detected, and they may therefore be considered as plausible SOA components eventually formed in normal or more extreme OH-radical-mediated photooxidation of biogenic isoprene.
Santos
Leonardo Silva
LS
ThoMSon Mass Spectrometry Laboratory, Institute of Chemistry, State University of Campinas, 13083-970, Campinas, SP, Brazil.
Dalmázio
Ilza
I
Eberlin
Marcos N
MN
Claeys
Magda
M
Augusti
Rodinei
R
D000336:Aerosols / Q000737:chemistry; D000393:Air Pollutants / Q000737:chemistry* / Q000528:radiation effects; D001272:Atmosphere / Q000737:chemistry; D002070:Butadienes / Q000737:chemistry* / Q000528:radiation effects; D004784:Environmental Monitoring / Q000379:methods*; D004896:Erythritol / Q000032:analysis; D045782:Hemiterpenes / Q000737:chemistry* / Q000528:radiation effects; D017665:Hydroxyl Radical / Q000737:chemistry* / Q000528:radiation effects; D010084:Oxidation-Reduction; D010316:Particle Size; D010420:Pentanes / Q000737:chemistry* / Q000528:radiation effects; D010777:Photochemistry; D011108:Polymers / Q000032:analysis*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism; D013402:Sugar Alcohols / Q000032:analysis
D000336:Aerosols; D000393:Air Pollutants; D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D011108:Polymers; D013402:Sugar Alcohols; C024617:polyol; C005059:isoprene; D017665:Hydroxyl Radical; C003460:threitol; D004896:Erythritol