AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Towards Quantitative Organic Aerosol Sampling with an Extractive Electrospray Ionization Time-of-Flight Mass Spectrometer (EESI-TOF)
JAY G. SLOWIK, Felipe Lopez-Hilfiker, Veronika Pospisilova, Lu Qi, Giulia Stefenelli, Yandong Tong, Alexander Lucas Vogel, Liwei Wang, Bin Yuan, Mao Xiao, Wei Huang, Claudia Mohr, Josef Dommen, Imad El Haddad, Urs Baltensperger, Andre S.H. Prévôt, Paul Scherrer Institute
Abstract Number: 483 Working Group: Instrumentation and Methods
Abstract Online aerosol mass spectrometry has significantly advanced our understanding of organic aerosol (OA) sources, composition, and aging processes. The new extractive electrospray ionization time-of-flight mass spectrometer (EESI-TOF) improves on previous measurement techniques by enabling rapid, online measurement of OA without thermal decomposition or ionization-induced fragmentation. The measured ion signals are proportional to mass concentration, although the relative response varies with molecular identity. Thus, while quantitative sampling by the EESI-TOF is attainable for analyte molecules for which calibration standards are measured, the large number and often unknown structure of OA components necessitates additional strategies for quantification.
Here we utilize inter-comparison studies between the EESI-TOF and other measurement techniques, including aerosol mass spectrometry (AMS) and chemical ionization mass spectrometry (CIMS), to constrain the EESI-TOF response to a range of ambient and environmentally-relevant systems. AMS measurements are used to constrain the EESI-TOF response in terms of total mass and bulk atomic ratios, while the response to individual ions is characterized in comparison to CIMS measurements. We investigate selected chemical standards, oxidation of model compounds (e.g. squalane, toluene, phenol, α-pinene) and real-world emissions (e.g. wood burning, coal, passenger vehicles), summer and winter ambient measurements from urban and rural field campaigns, and re-nebulized aerosol from a yearly cycle of collected filter samples from Zurich, Switzerland. The wide range of molecular weights, oxidation states, and functionalities measured provides a comprehensive assessment of the EESI-TOF response to environmentally-relevant OA and its potential for quantitative analysis.