Environmental SEM and x-ray microanalysis of biological materials

Environmental scanning electron microscopy (ESEM) permits the examination and analysis of uncoated biological specimens in the fully-hydrated wet state. The application of x-ray microanalysis (XRMA) to ESEM encounters two major problems atmospheric effects and specimen damage. The presence of a gaseous atmosphere results in a loss of spatial XRMA resolution due to beam skirting, an xray contribution from the atmosphere and a reduced overall x-ray count. Operational parameters can be optimised and corrections made to reduce these effects. Beam damage to the specimen involves mass loss, fine-structural changes, cross-linking of polymers and oxidation/hydrolysis reactions. Migration of cations and anions in relation to the probe spot may be particularly important for XRMA.