Chemical Ionization Mass Spectrometric Instrument for Multiple Species Measurements from a Remotely Piloted Vehicle

An atmospheric pressure chemical ionization mass spectrometer (APCIMS) will be designed to optimally measure a variety of gaseous species involved in marine boundary layer chemistry and condensation processes. The design of the instrument will modify prior technology, developed at the Geophysics Directorate of the Air Force Phillips Laboratory, to be included in the payload of a remotely piloted, long duration research aircraft. Improvements in reducing the instrument's weight and power consumption will be required, and sensitivity may need to be increased by upgrading to a triple quadrupole mass spectrometer. The chemical ionization mode of the instrument is used for maximum sensitivity in which the mass spectrometer is used as the detector in a fast flow ion reactor. The instrument is capable of measuring a number of species including, S02, S03, CH3SO3H, H2SO4, NO, NO2, HNO2, and HN03 in its negative ion mode and NH3 and other amines in a positive ion mode. It may also be possible to measure dimethyl sulfide (DMS). These species include many of the most important marine boundar layer species. Sensitivity in the chemical ionization mode is approximately 105 molec cm-3 with a time scale of 10 s in the lower troposphere.