Hydroxyapatite (HA), Ca₁₀(PO₄)₆(OH)₂ is an important biomaterial, as it is able to bond chemically to bone. In clinical applications of dental reconstruction and hip replacement, hydroxyapatite has found wide and accepted use as a source material for plasma sprayed, bonelike coatings deposited onto metallic substrates.

With the advent of mass production of hydroxyapatite-coated devices, reliable measures have to be implemented to assure their chemical integrity. One important and strongly regulated quality indicator of HA is its Ca/P molar ratio. A successful and  precise method for the determination of the molar Ca/P ratio in hydroxyapatite is X-ray spectroscopy (XRF). This method, especially in combination with the determination of the crystalline/amorphous ratio of HA by X-ray diffraction method (XRD), provides a suitable procedure for the reliable quality control of hydroxyapatite.