Dual-excitation-wavelength fluorescence spectra and elastic scattering for differentiation of single airborne pollen and fungal particles

Fluorescence spectra of aerosolized pollen (12 species or subspecies) and fungal (4 species) samples measured using a Dual-excitation-wavelength Particle Fluorescence Spectrometer (DPFS) are reported. The DPFS records two fluorescence spectra and two elastic scattering intensities from single airborne particles as they flow through an optical cell. Each particle is illuminated sequentially, first with a pulse from a 263-nm wavelength laser, followed by a second pulse from a 351-nm laser. The two dispersed fluorescence spectra (from 280 nm–700 nm) and elastic scattering intensities are measured by a single 32-anode photomultiplier tube. Principal component analysis (PCA) of the spectra is used to examine differences in the spectra. Plots of several principal components show that samples of pollens and fungal materials can largely be differentiated. These preliminary results suggest that fluorescence spectra and elastic scattering may be useful for real-time discrimination among a variety of airborne pollens, fungal materials, and other airborne particles.