Analytical capability to identify the principal molecular species present in microparticles is demonstrated on the basis of Raman spectra of selected compounds and materials. Among the inorganic species studied are sulfates, nitrates, carbonates and oxides, for which Raman spectra are discussed for single, solid particles of size down to 1 micrometer. The method of micro-Raman analysis is applied to the molecular characterization of individual microparticles from power plant emissions. Raman spectra have been obtained from microparticles of oil-fired power plant emissions collected by the EPA with cascade impaction samplers. Vanadium pentoxide, V2O5, has been identified as a major component of microparticles present in such samples. The presence of certain other vanadium containing species such as vanadyl, VO(+2), and ortho-vanadate, VO4(-3), is not indicated from the results of these measurements. Other Raman spectra show evidence of crystalline sulfate, SO4(-2), as a species present in major proportions. However, the exact nature of the associated cation specie(s) has not been determined. Many of the spectra obtained from fly ash particles show Raman bands characteristic of polycrystalline graphite apparently due to the presence of carbonaceous material associated with the particles.

"EPA-600/2-78-193." EPA IAG-D6-F012; EPA project officer: John Nader. References: p. 36-37.