American Association for Aerosol Research - Abstract Submission

AAAR 36th Annual Conference
October 16 - October 20, 2017
Raleigh Convention Center
Raleigh, North Carolina, USA

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A New Single Particle Aerosol Mass Spectrometer: Multiple-Analyses of the Same Individual Airborne Aerosol Particle for Determination of Particle Size, Polycyclic Aromatic Hydrocarbon-Content as well as the Elemental Composition

Johannes Passig, Julian Schade, Matthias Fuchs, Markus Oster, Martin Sklorz, Sven Ehlert, RALF ZIMMERMANN, Helmholtz Zentrum München and Rostock University, Germany

     Abstract Number: 151
     Working Group: Instrumentation and Methods

Abstract
Single-particle aerosol mass spectrometry (ATOFMS etc.) based on laser desorption ionization (LDI) is a versatile method for characterization of airborne particles. Currently available ATOFMS-technologies detect mainly inorganic species. Organics, such as polycyclic aromatic hydrocarbons (PAH), are important for aerosol-related health effects. Recently also field-applicable ATOFMS-approaches were developed, allowing on-line single particle PAH-detection (Bente et al., Anal.Chem. (2018) 8991-9004). For this in the ATOFMS-ion source particles are IR-laser pulse desorbed (LD). 1µs later, PAH are softly ionized by an UV-laser pulse (resonance-enhanced multiphoton ionization, REMPI) and ATOFMS-detected. A drawback is, however, that the LDI-information on the inorganic particle-composition is lost.

Here we present a new multi-step laser ionization ATOFMS-concept for detection of organic species (LD-REMPI) and element signatures (LDI) from individual aerosol particle. The approach is based on the sequential application of laser pulses to the very same particle and extraction field polarity-inversion of the dual-TOF mass analyzer between the REMPI- and LDI-laser ionization processes. The sized particle in the ion source it is IR-laser pulse desorbed and the PAH in the desorption plume subsequently are ionized by an UV-laser pulse (REMPI). After some 100 ns, when the PAH-ions have left the ion source, the field in the ion source is reversed and the same particle core, which is still on its fly-through path in the ion source, is hit by a third, intense laser pulse for LDI. Due to the inverted field the LDI-cations now are accelerated in the second TOF-Flight analyzer. By this procedure in addition to the particle size, the REMPI-spectrum of the absorbed PAH-molecules as well as the LDI-spectrum (showing e.g. Fe+, C+ or Al+) from the same individual particles are detected. First measurements of redispersed wood-combustion and diesel-emission particles as well as ambient sampling results are shown. On-line multi-step ATOFMS represents a promising technology for source apportionment and internal and external mixing state-analysis of inorganics and organics.