ESTIMATION OF SECTION THICKNESS AND QUANTIFICATION OF IRON STANDARDS WITH EELS

The possibilities of using electron energy-loss spectroscopy (EELS) for quantification of elemental concentrations in ultrathin sections are examined. Dynabeads, which are polystyrene beads with a known iron content, are proposed as internal iron standards. The quantity of an element present depends on the thickness of the specimen. A prerequisite for estimation of absolute section thicknesses with EELS is the knowledge of the mean free path lambda of electrons in the specimen. This factor is determined for the embedding resins Epon and Nanoplast by comparing EELS data with directly observed thicknesses in re-embedded sections. Dynabeads were found to include iron in a homogeneous distribution and to be stable in the electron beam.