Abstract
Abstract. A new method for size-resolved chemical analysis of nucleation mode aerosol particles (size range from ∼10 to ∼30 nm) is presented. The Thermal Desorption Differential Mobility Analyzer (TD-DMA) uses an online, discontinuous principle. The particles are charged, a specific size is selected by differential mobility analysis and they are collected on a filament by electrostatic precipitation. Subsequently, the sampled mass is evaporated in a clean carrier gas and analyzed by a chemical ionization mass spectrometer. Gas-phase measurements are performed with the same mass spectrometer during the sampling of particles. The characterization shows reproducible results, with a particle size resolution of 1.19 and the transmission efficiency for 15 nm particles being slightly above 50 %. The signal from the evaporation of a test substance can be detected starting from 0.01 ng and shows a linear response in the mass spectrometer. Instrument operation in the range of pg m−3 is demonstrated by an example measurement of 15 nm particles produced by nucleation from dimethylamine, sulfuric acid and water.
Highlights
Aerosol particles play an important role in the earth’s climate
For the component used here, the conversion factor k is 42.95 ng−1. Their individual ionization efficiencies relative to that of the test substance need to be taken into account and a mass spectrometer signal Si relates to a mass of mi = k · RIEi · Si
The Thermal Desorption Differential Mobility Analyzer (TD-DMA) is suitable for measuring nucleation and Aitken mode particles and is successfully analyzing aerosol mass concentrations in the pg m−3 range
Summary
Aerosol particles play an important role in the earth’s climate. They influence the radiative budget directly by scattering and absorbing solar radiation, and indirectly by changing cloud properties such as albedo and lifetime. The thermal desorption chemical ionization mass spectrometer (TDCIMS) (Voisin et al, 2003; Smith et al, 2004; McMurry et al, 2009) is a size-resolved method collecting particles electrostatically and using thermal desorption to measure the particle-phase composition. The Filter Inlet for Gases and AEROsols (FIGAERO) (Lopez-Hilfiker et al, 2014) is a bulk-phase filter sampler using thermal desorption It does not provide size-resolved information, it is able to measure both gas and particle phase and to investigate partitioning effects (Lopez-Hilfiker et al, 2015). The Thermal Desorption – Differential Mobility Analyzer (TD-DMA) is capable of measuring in a size-resolved and integral setting It allows taking gas-phase measurements with the same mass spectrometer. The signal is quantified (Sect. 5) and the results are discussed (Sect. 6), closing with a short summary (Sect. 7)
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