Determination of the local chemistry of iron in inorganic and organic materials

The systematic EELS analysis of a series of naturally occurring, synthetic and biological samples has provided a framework from which Fe valence of unknown materials can be determined and the relative ratios of the valences present can be calculated. The quantification of the relative ratios of Fe3+/Fe2+ is possible via the fitting of Gaussian or Voigt (with 89.3% Gaussian contribution) line profiles to the Fe L3-edge. The ratio of Fe3+/ΣFe is determined from the areas under the fitted peaks. The method is robust and has an error in the range of <10% on Fe3+/ΣFe for samples with >2 atom% Fe. We present applications of this method including the investigation of polaron hopping in calcic amphibole, the quantification of Fe3+/ΣFe in clay minerals from deep water sediments, quantification of Fe valence in human liver tissue and the determination of Fe valence in airborne particulate matter.