Accurate determination of the Ca:P ratio in rough hydroxyapatite samples by SEM-EDS, PIXE and RBS-a comparative study

The Ca:P ratio in a certified standard of hydroxyapatite was determined by Xray spectrometry (XRS), with the X-rays excited by both electrons and ions using energy dispersive spectroscopy on the scanning electron microscope (SEM-EDS) and particle induced X-ray emission (PIXE). The certified value of Ca:P was accurately verified by 3 MeV 4 He + Rutherford Backscattering Spectrometry (RBS). We show that the demonstrably rough surface of this sample does not cause perturbation of the Ca:P ratio within the uncertainties of each of the XRS measurements.