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Time of flight mass spectrometer in closeup shot with blue light
Intothelight Photo - stock.adobe.com

Single-particle mass spectrometry of aerosols

 

For the assessment of potential health effects and the understanding of atmospheric processes, the mixing state of aerosols is of importance. In particular, potential harmful substances can be distributed as internal mixture (low concentration on all particles) or as external mixture (single particles with high concentration and e.g. potential mutagenic activity). Single particle techniques can inherently address this issue, but are technically challenging. Key approach is the Aerosol-Time-of-Flight (ATOF) method (Hinz et al., 1994; Prather et al., 1994; Pratt & Prather, 2012). Herein, individual particles are aerodynamically accelerated into vacuum and detected via Mie-scattering in a pair of laser beams (see Fig. 1a). The flight time between both laser beams provides information on the particle size and its (real-time calculated) arrival time in the center of a bipolar mass spectrometer. Here the particle is hit by an UV laser pulse leading to desorption and ionization (LDI) of elements and molecular fragments. Their typical signatures in mass spectra allow for a classification and apportionment of the individual particles to specific sources. Our goal is the extension of this method to smaller particles below 200 nm size, which are e.g. important condensation nuclei in the atmosphere and can be transported deep into the human lung, and to bioaerosols, e.g. pollen, for future environmental monitoring.

Single-particle mass spectrometry of aerosols

 

For the assessment of potential health effects and the understanding of atmospheric processes, the mixing state of aerosols is of importance. In particular, potential harmful substances can be distributed as internal mixture (low concentration on all particles) or as external mixture (single particles with high concentration and e.g. potential mutagenic activity). Single particle techniques can inherently address this issue, but are technically challenging. Key approach is the Aerosol-Time-of-Flight (ATOF) method (Hinz et al., 1994; Prather et al., 1994; Pratt & Prather, 2012). Herein, individual particles are aerodynamically accelerated into vacuum and detected via Mie-scattering in a pair of laser beams (see Fig. 1a). The flight time between both laser beams provides information on the particle size and its (real-time calculated) arrival time in the center of a bipolar mass spectrometer. Here the particle is hit by an UV laser pulse leading to desorption and ionization (LDI) of elements and molecular fragments. Their typical signatures in mass spectra allow for a classification and apportionment of the individual particles to specific sources. Our goal is the extension of this method to smaller particles below 200 nm size, which are e.g. important condensation nuclei in the atmosphere and can be transported deep into the human lung, and to bioaerosols, e.g. pollen, for future environmental monitoring.