Compound identification in organic aerosols using temperature-programmed thermal desorption particle beam mass spectrometry

Identification of organic compounds in multicomponent organic aerosols is demonstrated using temperature-programmed thermal desorption particle beam mass spectrometry. Aerosol particles are efficiently sampled into a high-vacuum chamber using aerodynamic focusing techniques followed by impaction onto a cold metal foil. The sample is then slowly heated to achieve temporal separation of components according to their vapor pressures, while evaporating compounds are continuously mass-analyzed using a quadrupole mass spectrometer, Mass spectra of the individual components are then extracted from time-dependent spectra. Measurements made using aerosols containing equal-mass mixtures of various carboxylic acids and dioctyl sebacate indicate that, using this setup and a temperature ramp rate of similar to 1 degrees C/min, useful separation can be achieved for compounds having a factor of 5 or more difference in vapor pressures. The technique is demonstrated for use in laboratory environmental chamber studies of aerosol chemistry by analyzing the secondary organic aerosol generated from the reaction of 1-tetradecene and ozone in excess 2-propanol. Temperature-programmed thermal desorption is shown to be a valuable tool which can be used in conjunction with quantitative thermal desorption particle beam mass spectrometry for chemical analysis of components in secondary organic aerosol formed in laboratory environments.