Organic hydroxy acids as highly oxygenated molecular (HOM) tracers for aged isoprene aerosol

Highly oxygenate molecules (HOMs) are a class of compouns associate with seconary organic aerosols exhibiting high oxygen to carbon (O:C) ratios an often originating from the oxiation of biogenic compouns. Here, the photooxiation an ozonolysis of isoprene were examine uner a range of conitions to ientify HOM tracers for age isoprene aerosol. The HOM tracers were ientifie as silylate erivatives by gas chromatography-mass spectrometry an by etecting their parent compouns by liqui chromatography-high resolution mass spectrometry. In aition to the previously observe methyltetrols an 2-methylglyceric aci, seven tracer compouns were ientifie, incluing 2-methyltartronic aci (MTtA), 2-methylerythronic aci (2MeTrA), 3-methylerythronic aci (3MeTrA), 2-methylthreonic aci (2MTrA), 3-methylthreonic aci (3MTrA), erythro-methyltartaric aci (e-MTA), an threo-methyltartaric aci (t-MTA). The molecular structures were confirme with authentic stanars synthesize in the laboratory. The presence of some of these HOMs in the gas an particle phases simultaneously provies evience of their gas/particle partitioning. To etermine the contributions of age isoprene proucts to ambient aerosols, we analyze ambient PM2.5 samples collecte in the southeastern Unite States in summer 2003 an at two European monitoring stations locate in Zielonka an Goów (Polan). Our finings show that methyltartaric acis (MTA) an 2- an 3-methylthreonic acis (an their stereoisomers) are representative of age isoprene aerosol because they occur both in the laboratory chamber aerosol obtaine an in ambient PM2.5. On the basis of gas chromatography-mass spectrometry (GC-MS) analysis, their concentrations were foun to range from 0.04 ng for 3-methylthreonic aci to 6.3 ng m-3 for methyltartaric aci at the southeast site in Duke Forest, NC, USA. Copyright