Physical and chemical (Raman) characterization of bioaerosols - Pollen

The chemical characterization of pollen is explored using fluorescence spectroscopy and two Raman spectroscopic techniques. The on-line Raman technique involves trapping single pollen particles in an electrodynamic balance coupled to a Raman spectrometer. The off-line method requires the pollen samples to be deposited on a substrate and analyzed using a Raman microprobe. It is shown that fluorescence spectra of various grass and tree pollens do not show sufficient differences to provide an adequate method for characterizing them. Furthermore, the strong fluorescence masks any underlying Raman spectra. Although photochemical bleaching can reduce the fluorescence signal, it is shown that use of a near-IR laser provides Raman signals that can be used to characterize the pollen particles. In the on-line system, the particle density was determined From electrodynamic springpoint measurements and the geometric pollen size measured with a video microscope. (C) 2000 Elsevier Science Ltd. All rights reserved.