EELS-ESI Identification of Heterogeneous Suspensions of Aquatic Microparticles

Abstract

Abstract. 2014 Submicron mineral particles in freshwaters represent an important proportion of the total particle number. These microparticles are frequently associated to macromolecular organic matter and have a high specific surface area; they might thus be strong heavy metal and nutrient scavengers in aquatic systems. Their non-artefacted characterization at the level of individual particles represents a promising challenge, while preservation of the undisturbed state of natural fragile specimens is a prerequisite. We have used a TEM-EELS-ESI procedure which allows the identification of mineral microparticles in individual model suspensions of iron oxides, aluminum oxides and clays in the presence of polysaccharides, at concentrations typical of natural levels. As expected, core-loss ionization edge intensities measured by this method are limited by the thickness of particles. Heterogeneous mixtures of the former microparticles/macromolecules were prepared in order to mimic natural specimens. Under optimum analytical conditions, it was possible to extract the very nature of these entities, to reveal low electron-density polysaccharides and even to identify microparticles masked within complex aggregates.

Use of analytical microscopy to analyze the speciation of copper and chromium ions onto a low-cost biomaterial

“…On the contrary, EELS, which directly measures the energy loss of incident electrons inelastically scattered from atoms, is a direct probe of the electron configuration around atoms and can determine the oxidation state of 3d and 4d transition metals with a high spatial resolution [9][10][11]. TEM-EELS techniques have been used for many years in Materials Sciences and have recently found applications in biology and environmental sciences [11][12][13][14][15].…”

Quantitative and qualitative characterization of aquatic iron oxyhydroxide particles by EF‐TEM

“…For the characterization of aquatic particles ( Mavrocordatos et al ., 1994 ; Perret et al ., 1995 ), we use mainly EELS on whole‐mount specimens analysed at 80 keV with an on‐column Castaing–Henry energy filter (EF‐TEM; Castaing & Henry, 1962). The variable thickness of the particles under investigation means that special attention should be given to the interpretation of the results because of spatial inhomogeneities in multiscattering processes originating from thick regions, and because of weak signals produced by thin regions of the particles.…”

Enhanced visualization of polysaccharides from aqueous suspensions

“…In previous studies [18,24] we have shown with aquatic suspensions (mineral particles and organic matter) that EF-TEM can be applied to (i) elemental analysis (spectrum mode; electron energy loss spectrometry, EELS-TEM), (ii) elemental mapping (imaging mode; electron spectroscopic Imaging, ESI-TEM), and (iii) the visualization of organic matter (structure-sensitive mode; contrast tuning, CT-TEM). The last technique has been selected and optimized in this work to enhance contrasting of polysaccharide fibrils.…”