Fully quantitative imaging of chemical elements in Arabidopsis thaliana tissues using STIM, PIXE and RBS

An experimental design based on nuclear microprobe techniques has been carried out for a complete characterization of major and trace element contents, and distributions, in biological samples. A new methodology, deriving from the "Q-factor", was developed in order to assess the entire sample composition, including the hydrogen content. This methodology relies on a combination of STIM, mu-PIXE and mu-RBS techniques. The STIM analysis allows the determination of initial sample mass as needed for trace element mass normalization. Then mu-PIXE and mu-RBS analyses were performed simultaneously in order to measure respectively trace elements, carbon, nitrogen and oxygen contents. The variation from the "Q-factor" method lies in the fact that Q was not determined from RBS carbon peak height, because of the hydrogen content dependency of carbon peak height, but from RBS gold signal height as occurring from back-scattering of particles on a thin gold foil placed onto each sample. Consequently the absolute carbon content could be measured, as well as, indirectly, the hydrogen content. The STIM, mu-PIXE and mu-RBS were also used to quantitatively map chemical elements within samples at a sub-cellular scale. Application to the chemical imaging of Arabidopsis thaliana tissues contaminated with caesium will be presented. (c) 2005 Elsevier B.V. All rights reserved.