Aerosol fluorescence spectrum analyzer for rapid measurement of single micrometer-sized airborne biological particles

We report the operation of an aerosol analyzer capable of measuring the fluorescence spectra of single micrometer-sized bioaerosol particles as they flow through the instrument. Particles entrained in an airstream initially traverse a cw, (continuous wave) (488 nm) "trigger" laser beam where their elastic scattering and total fluorescence is measured with photomultipliers. When the elastic scattering and/or fluorescence signals exceed preset levels, a 266 nm UV "probe" laser is triggered to fire and illuminate preselected particles downstream from the trigger laser. The UV laser-excited spectra of particles are measured with the instrument's image-intensified CCD detector that is gated to be on when the probe laser fires. We demonstrate the ability of the instrument to capture the fluorescence spectra of single micrometer-sized airborne biological particles. Such spectra should be useful in differentiating between biological and nonbiological aerosols and in partially characterizing airborne biological particles. (C) 1998 American Association for Aerosol Research.