Characterization and application of in-vacuum PIXE/EBS system for the direct elemental analysis of thick solid biological samples

Utilization of combined particle-induced X-ray emission (PIXE) and elastic backscattering (EBS) spectrometry for the direct elemental analysis of thick solid biological samples was thoroughly discussed. Powdered samples pressed as pellets were directly analyzed. Combination of applying low ion beam currents, random scanning of the sample across the beam during data acquisition, and using special sample holder enabled effective minimization of local ion beam heating. This subsequently inhibited potential element loss during ion beam irradiation. Matrix elements were determined from multiple EBS spectra, which were acquired using three different ion beam energies. Subsequently, averaging of the elemental concentrations obtained was achieved using novel MultiSIMNRA software. Moreover, combined EBS spectrometry, nuclear reaction analysis (NRA), and elastic recoil detection analysis (ERDA) measurements were used to overcome the limitations of using EBS separately and subsequently obtain accurate matrix element concentrations. The validity of the PIXE/EBS system for the direct elemental analysis of thick biological samples was comprehensively evaluated. The obtained concentration values demonstrated reliable results for most investigated elements (5-15%), starting from sodium onwards. The non-satisfying results were evaluated and justified.