Conventional, pulsed and high-field electron paramagnetic resonance for studying metal impurities in calcium phosphates of biogenic and synthetic origins

Abstract

© 2018 Elsevier B.V. Calcium phosphates (CaP) based materials are widely recognized as the most suitable matrix for bone tissue engineering. The cationic and anionic substitutions of CaP structure by the elements and groups of biological importance seem to be the effective ways to improve the properties of CaP-based substances to achieve the material's desired parameters. Various analytical and biochemical methods are used for controlling their chemical content, structure, morphology, etc. Unfortunately, magnetic resonance techniques are usually not even considered as necessary tools for CaP inspection. Some aspects of application of the commercially realized electron paramagnetic resonance (EPR) approaches for characterization of CaP powders and ceramics (including the nanosized materials) such as hydroxyapatite and tricalcium phosphates of biogenic and synthetic origins containing intrinsic impurities or intentional dopants are demonstrated. Among them (1) conventional approaches; (2) high-frequency approaches – for measuring small amount of material; (3) pulsed methods – to study size effects, effects of the co-doping by different sorts of ions, to determine the location of paramagnetic centers, etc. The key features and advantages of the EPR techniques for CaP based materials characterization that could complement the data obtained with the recognized analytical methods are stressed.