AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
In-Situ Chemical Characterization of Sub-micron Organic Aerosols Using Direct Analysis in Real Time Mass Spectrometry (DART-MS): The Effect of Aerosol Size and Volatility
MAN NIN CHAN, Theodora Nah, Kevin Wilson, Lawrence Berkeley National Laboratory
Abstract Number: 499 Working Group: Aerosol Chemistry
Abstract Direct Analysis in Real Time (DART) mass spectrometry is an atmospheric pressure ionization technique suitable for in situ chemical analysis of organic aerosols. The mass spectra are obtained by introducing a stream of nanometer-sized aerosols into the ionization region, which is an open space between the DART ionization source and the atmospheric inlet of mass spectrometer. Model single component aerosols are used to show how the aerosol size and volatility influence the measured ion signals at different DART gas temperatures.
We found that for equivalent aerosol mass concentrations, the ion signal scales with particle surface area, with smaller diameter oleic acid aerosols yielding higher ion signals relative to larger diameter aerosols. For the aerosols of the same size, but different vapor pressures, the ion signal is larger for more volatile succinic acid aerosols than less volatile adipic and suberic acid aerosols. While the aerosols are not completely vaporized in the ionization region, the radial probing depth for these model aerosols range from 1 to 10 nm. The magnitude depends upon the physiochemical properties of the aerosols and DART gas temperature. An aerosol evaporation model is proposed to explain the correlation between the measured ion signal and aerosol size and volatility. We also demonstrate the potential application of DART for in situ chemically analyzing wet aerosol particles.