Real-time Chemical Analysis of Aerosol Particles Using an Ion Trap Mass Spectrometer

Abstract

Chemical analysis of aerosol particles in real time has been demonstrated using laser desorption mass spectrometry in an ion trap. Airborne particulates were extracted from the air directly into a vacuum system through a capillary and a skimmer with differential pumping. The injected particles were detected individually at two positions by fiberoptic based optical detectors. The velocity of the particle was estimated by the time difference between them and used to predict the arrival time at the center of the ion trap, so that a Nd:YAG laser could be fired exactly on time to desorb/ablate the particle. The desorbed and ionized species from the microparticle were analyzed by the ion trap mass spectrometer (ITMS). The sample aerosol particles were generated by nebulizing salt solution into the air through an orifice with a Piezoelectric vibrator. Mass spectra of potassium nitrate particles with a size of 15 Am in diameter extracted directly from the air have been measured. The velocity distribution of potassium nitrate particles (15{mu}m) extracted through a capillary with a inner diameter of 0.5 mm was found to have a maximum at 160 m/s. The electronic timing control system that measures the velocity of the individual microparticle and triggers themore » desorption laser to intercept the fast moving microparticle will be discussed.« less