Direct and rapid quantification of calcium phosphate precipitate on titanium by X-ray fluorescence analysis using fundamental parameter method

In the present study, we propose a characterization technique to determine the amount of calcium phosphate (CP) precipitate formed on a titanium substrate. The quantitative analysis of the CP precipitate on a metallic substrate is significant for researchers of metallic biomaterials because CP that spontaneously precipitates in a simulated-body fluid gives information on the bioactivity of the metallic biomaterials. We focused on X-ray fluorescence (XRF) analysis and adopted the thin-film fundamental parameter method (thin-film FP method) because it allows direct (non-pretreatment) and rapid quantitative analysis without any reference materials. We show that XRF analysis using the thin-film FP method can be adequately applied to the quantitative analysis of the CP precipitate in the simulated-body fluid immersion test. We also show that the density of the CP-precipitate layer can be estimated by combining the XRF results with images of cross-sectional scanning electron microscopy (SEM). Consequently, XRF analysis combined with the thin-film FP method can provide a convenient means to evaluate the CP precipitate on a titanium substrate, which improves the accuracy and accessibility of the simulated-body fluid immersion test.