ENERGY-FILTERED TRANSMISSION ELECTRON-MICROSCOPY FOR THE PHYSICOCHEMICAL CHARACTERIZATION OF AQUATIC SUBMICRON COLLOIDS

A combination of energy filtered transmission electron microscopic (EF -TEM) procedures is proposed for the non-perturbing physico-chemical c haracterization of submicron mineral and organic colloids in aquatic s ystems. Synthetic hematite microparticles and xanthan polysaccharides were used as well-characterized model colloids in order to determine t he optimum EF-TEM analysis conditions. In this paper, it is demonstrat ed that (i) our model colloids are morphologically representative of n aturally occurring mineral/organic associations, (ii) EF-TEM allows th e detection of fine xanthan ultrastructures without artefacts of conve ntional staining methods and (iii) submicron hematite particles can be specifically visualized and spectrometrically measured by EF-TEM with in a hematite/xanthan mixture. This EF-TEM procedure appears to be app ropriate for the characterization of real aquatic samples.