PIXE and RIXRF comparison for applications to biological sample analysis

The different excitation methods of X-ray spectral analysis with proton induced X-ray emission (PIXE) and radioisotope (Cd-109) induced X-ray fluorescence (RIXRF) are evaluated and compared with regard to sensitivity, detection limit, precision, accuracy and cost, using NIST orchard leaves and pine needles standard reference materials. The accuracy and precision of both the methods for biological analysis using appropriate standards are shown to be better than 5%. The comparison of sensitivity results indicates that PIXE is comparatively more sensitive for light elements (K to Zn) and RIXRF for heavier elements (Z > 33), the crossing points being at Z = 33. Based on the present findings, PIXE is recommended for the analysis of bio-environmental samples containing low level biologically important trace elements in the range of Z = 19-30. PIXE techniques have been applied here to the analysis of 10-15 elements in some biological samples and standards with good accuracy and precision without prior pre-concentration except oven or freeze drying; a combination of PIXE and RIXRF represents a complete investigation tool for the analysis of 15-20 light and heavy elements. (C) 2004 Elsevier B.V. All rights reserved.