AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Intercomparison of an EESI-TOF with VOCUS-PTR for Quantitative Aerosol Analysis
DONGYU S. WANG, Chuan Ping Lee, Jordan Krechmer, Manjula Canagaratna, Francesca Majluf, Yandong Tong, Josef Dommen, Andre S.H. Prévôt, Imad El Haddad, David Bell, Jay G. Slowik, Urs Baltensperger, Paul Scherrer Institute
Abstract Number: 257 Working Group: Instrumentation and Methods
Abstract Online characterization of aerosol composition at the near-molecular level has recently become possible with the development of extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF), which is capable of detecting lightly oxygenated to highly oxygenated organic molecules (HOM) with minimal fragmentation. Good correlations between the EESI-TOF, aerosol mass spectrometer (AMS) and Filter Inlet for Gases and AEROsols (FIGAERO) measurements were observed in recent studies, but the ion-to-mass response factors in complex samples remain unaddressed.
In this study, we investigated the EESI-TOF sensitivity to a variety of secondary organic aerosol components, including monoterpene ozonolysis and OH-aromatic oxidation products. Seed particles were introduced as condensation nuclei to promote gas-to-particle partitioning. An AMS was used to quantify the inorganic seed and bulk organic aerosol mass concentrations. A VOCUS proton-transfer mass spectrometer (VOCUS-PTR) was used to quantify lightly-to-moderately oxygenated organic compounds in the gas-phase. Condensation sink was enhanced by increasing the seed particle concentration, driving gas-phase condensation and particle-phase growth. The EESI-TOF sensitivity can be derived from the relative changes in EESI-TOF and VOCUS-PTR signals.
The EESI-TOF was able to measure O1 to O9 oxidation products in the particle phase in response to seed particle injections. Comparison with the VOCUS-PTR indicates that the EESI-TOF has higher sensitivities towards more oxygenated organic species. Comparison with the AMS indicates that the EESI-TOF responds quantitatively to the inorganic seed particles. Results here demonstrate the EESI-TOF’s potential to quantify individual species in complex samples without direct calibration using a chemical standard.