Constraining the response factors of an extractive electrospray ionization mass spectrometer for near-molecular aerosol speciation

Abstract. Online characterization of aerosol composition at the near-molecular level is key to understanding chemical reaction mechanisms, kinetics, and sources under various atmospheric conditions. The recently developed extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) capable detecting a wide range organic oxidation products in particle phase real time with minimal fragmentation. Quantification can sometimes be hindered by lack available commercial standards for constituents, however. Good correlations between EESI-TOF other speciation techniques have been reported, though no attempts yet made parameterize response factor different species. Here, we report first parameterization secondary (SOA) based on its elemental composition. SOA was formed ozonolysis monoterpene or OH aromatics inside an flow reactor (OFR) using ammonium nitrate as seed particles. A Vocus proton-transfer (Vocus-PTR) high-resolution (AMS) were used determine gas-phase molecular particle-phase bulk composition, respectively. EESI factors towards coating inorganic core constrained intercomparison AMS. highest observed produced from 1,3,5-trimethylbenzene, followed those d-limonene o-cresol, consistent previous findings. derived intercomparisons Vocus-PTR measurements found vary 103 106 ion counts s?1 ppb?1, mostly within ±1 order magnitude their geometric mean 104.6 ppb?1. For aromatic components, correlated weight oxygen content inversely volatility. agreed 20 isomers across biogenic systems. Parameterization measured formulae could reproduce empirically determined single volatile compound (VOC) system 5 configuration our spectrometers. results demonstrate that standard-free quantification possible.