AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Development of an Online Extractive Electrospray Ionization Time of Flight Mass Spectrometer (EESI-TOF): Application to Atmospheric Aerosol
FELIPE LOPEZ-HILFIKER, Veronika Pospisilova, Josef Dommen, Andre Prévôt, Urs Baltensperger, Tofwerk, Jay Slowik, Paul Scherrer Institute
Abstract Number: 288 Working Group: Instrumentation and Methods
Abstract Thermal desorption of aerosol components for analysis is typical in most online aerosol sampling instruments (e.g. AMS, ATOFMS, SPLAT, PALMS, TAG, FIGAERO). Thermal desorption leads to decomposition even at low temperatures (<100 C) significantly changing measured aerosol composition and properties, hindering mechanism development and source apportionment efforts.
We describe the development of an online extractive electrospray time-of-flight mass spectrometer (EESI-TOF) for fast molecular analysis of aerosol organics without heating induced fragmentation. This instrument couples an EESI inlet, recently developed at PSI to a high-resolution time of flight mass spectrometer. Briefly, the extractive electrospray instrument operating principle involves the collision of atmospheric aerosol with charged electrospray droplets. The soluble components are extracted into the electrospray droplet, and as the solvent from the electrospray evaporates, ion ejection results in gas phase ions formed from the extracted aerosol. Therefore aerosol are ionized rapidly, and transferred into the gas phase without any need for sample heating.
The EESI-TOF provides rapid response (1Hz) measurements of highly oxidized organic species and oligomers with individual compound detection limits as low as 1 ng m-3 in 5 seconds, allowing for the simultaneous retrieval of molecular compositions for hundreds of compounds that comprise organic aerosol at high time resolution. Online analysis of SOA from the reaction of a-pinene and ozone at in a flow tube and simulation chamber results in prompt formation of over 500 individual molecules (150 to 500+ Th) which are detected by the EESI-TOF with excellent signal to noise even for oligomeric species.
We present the detailed characterization of the EESI-TOF instrument and its application to atmospheric aerosol, both from chambers and ambient measurements. We discuss the instrument performance in the context of current aerosol measurement shortfalls, and potential applications of the instrument to the chemical speciation of organic aerosol at atmospherically relevant conditions.