Development, characterization, and refinement of a transportable aerosol time-of-flight mass spectrometer.

摘要

Since the first ATOFMS instrument was built in 1994, substantial improvements to the hardware and software which comprise the instrument have made it a more powerful, versatile tool for the analysis of atmospheric and other aerosols. We have designed and constructed second-generation ATOFMS instruments which are not only capable of measuring the size and composition of individual aerosol particles in situ, and in real-time, but are also transportable and can operate unattended for hours at a time. These instruments collect both positive and negative ion spectra from each particle, have extended dynamic range, and incorporate automated data collection and analysis software which makes the analysis of tens of thousands of spectra in a data set a manageable task.; We have attempted to better understand and characterize the laser desorption process by detecting and sizing fragments of particles which remain after desorption, and in the process have refined a particle detection and sizing technique based on charge saturation which may have other potential uses. We have also characterized the light scattering signal which is generated by the ATOFMS particle detection apparatus, with an eye toward extracting additional information about the optical properties of particles from this signal in future versions of the instrument. Finally, we have adapted the delayed ion extraction technique to ATOFMS, and demonstrated that it has the ability to increase the resolution of particle spectra.