Optimisation of Pt sensitivity in PIXE analysis of thin biological samples

To obtain Pt concentration distributions in tumor biopsies, micro-PIXE is used. The Limit of Detection (LOD) for Pt is determined by the background production cross section together with the production cross section for the Pt-L lines. Both are functions of the type and energy of the projectile. In order to optimise the experimental conditions, the proton energy is varied from 2.5 to 5 MeV and the corresponding X-ray spectra are analysed. The optimum LOD is about 1 mu g/g for a sample thickness of 1 mg/cm(2) and a total charge of 100 mu C. A study is performed to investigate the possibility of elemental analysis by means of alpha excitation. The corresponding LOD is 6 mu g/g with 200 mu C charge (He++ was used). For alpha excitation, sample damage limits the beam current and, thus, causes a tremendous increase in the measurement time. (C) 1998 Published by Elsevier Science B.V.