Rapid stoichiometric analysis of calcium‑phosphorus ratio on hydroxyapatite targets by one-point calibration laser-induced breakdown spectroscopy

Abstract

The calcium‑phosphorus ratio (Ca/P) has an important role in calcium phosphate applications, as a slight change in this ratio results in substantial modifications of their characteristics. Hydroxyapatite is a bioactive ceramic of the calcium phosphate family, and its composition and crystalline structure are similar to the human bone. For this reason, it is widely used to promote bone integration in prosthetics and scaffolds. Prosthetics are usually made of metal and coated with bioceramics and the some techniques used to make these coatings depositions conserve the stoichiometry from the target during deposition. Therefore, studying the target Ca/P is a way to guaranteeing the final deposition stoichiometry. In this study, we investigated the One Point Calibration – Laser Induced Breakdown Spectroscopy (OPC-LIBS) method for the measurement of the Ca/P of hydroxyapatite targets. This method is quantitative, based on the determination of correction parameters via analysis of a standard sample with known stoichiometry. Results were compared to well-established techniques of X-ray Fluorescence (XRF) and Atomic Absorption Spectroscopy (AAS) and showed that the deviation in the difference is less than 5%, proposing a substitute for elemental analysis. Moreover, this method has technical advantages such as rapid measurements, no need for sample preparation or destruction and easy automation.