Airborne extractive electrospray mass spectrometry measurements of the chemical composition of organic aerosol

Abstract. We deployed an extractive electrospray ionization time-of-flight mass spectrometer (EESI-MS) for airborne measurements of biomass burning aerosol during the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) study onboard NASA DC-8 research aircraft. Through optimization working solution, active control region pressure, precise capillary position, we achieved 1 Hz quantitative nitrocatechol levoglucosan concentrations up pressure altitudes 7 km. The EESI-MS response was calibrated each flight, with flight-to-flight calibration variability 60 % (1σ). Laboratory showed no size dependence in sensitivity below particle geometric diameters 400 nm, covering 82 accumulation-mode FIREX-AQ. also present a first in-field intercomparison chemical analysis online proton-transfer-reaction (CHARON PTR-MS) high-resolution Aerodyne (AMS). CHARON PTR-MS were well correlated, regression slope 0.94 (R2=0.77). AMS levoglucosan-equivalent greater difference, 1.36 (R2=0.96), likely indicating contribution other compounds measurement. total signal correlation (R2=0.9) organic measured by AMS, bulk standards.