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 L-3-edge. The ratio of Fe3+/Sigma Fe is determined from the areas under the fitted peaks. The method is robust and has an error in the range of < 10% on Fe3+/Sigma Fe for samples with > 2atom% Fe. We present applications of this method including the investigation of polaron hopping in calcic amphibole, the quantification of Fe3+/Sigma Fe 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. (c) 2004 Elsevier B.V. All rights reserved.