Calcium phosphate chemical characterization

The development of the types of skeletons that characterize Tommotian faunas constituted a major evolutionary event. Although skeletons are known to support soft tissue and to facilitate locomotion, such adaptive functions cannot explain why so many different kinds of skeletons developed suddenly in the early part of Tommotian time. It has been suggested that a chemical change within the oceans triggered the production of these skeletons, but this hypothesis does not explain why some skeletons were composed of calcium carbonate and others of calcium phosphate, two compounds with quite different chemical properties. The rapid evolution of various kinds of external skeletons is probably in part attributable to the fact that animals... 

Up to this point, we have summarized the NMR parameters of some selected crystalline compounds. Model crystalline compounds of calcium phosphates are important structural reference for the study of biominerals because the highly complex hierarchical structures of bones and teeth contain different phosphorus species such as unprotonated orthophosphate (PC>43 ) and protonated orthophosphate (HP042 ).70,77 It is beyond doubt that 31P chemical shifts are the most important spectroscopic parameters for the characterization of calcium phosphates. While the 31P chemical shift can reflect the protonation state of a phosphate species, 31P CSA is a sensitive measure of the symmetry of the electronic... 

While calcium phosphates are currently widely used as implants in the body, more detailed work on the role of chemically enriched apatites on the biological response, characterization of apatites and microstructural control will reveal the optimal characteristics of an apatite for clinical application. 

A number of laboratory studies have been recorded recently aimed at characterizing the kinetics of both the chemical reaction and crystallization steps in a reaction crystallization process. Examples of liquid phase reactions studied for this purpose are the crystallization of salicylic acid from aqueous solutions of sodium salicylate using dilute sulphuric acid (Franck et al, 1988) and the crystallization of various calcium phosphates by reacting equimolar aqueous solutions of calcium nitrate and potassium phosphate (Tsuge, Yoshizawa and Tsuzuki, 1996). Several aspects of crystal size distribution control in semi-batch reaction crystallization have been considered by Aslund and Rasmuson (1990) who studied the crystallization of benzoic acid by reacting aqueous solutions of sodium benzoate with HCl. An example of crystallization arising from a gas-liquid reaction in an aqueous medium is the precipitation of calcium carbonate from the reaction between calcium hydroxide and CO2 (Wachi and Jones, 1995). 

Mulliez MA, Wenz R. Physical-chemical characterization of a new magnesium containing calcium phosphate cement SOPRIM. European Society for Biomaterials Annual Meeting (ESB 2002) 2002 Sept 11-14, 2002 Barcelona. 

Amorphous Ca-P (ACP) is the first solid phase to appear in solution containing high concentrations of calcium and phosphate. ACP lacks the orderly internal structure of crystalline Ca-P compounds and typically has a spherical morphology [3 ]. Chemically, it has a Ca P ratio of around 1.5 and is characterized by the absence of diffraction peaks on x-ray diffraction (XRD) patterns. ACP is unstable in aqueous fluids and transforms into crystalline phases such as octacalciumphosphate (OCP) and apatite. Heating of ACP also results in conversion to poorly crystallized apatite (600 C), p-TCP (800 C, dry heat), or HA (800°C, humid heat) [4]. Therefore, ACP should be considered as a precursor for crystalline Ca-P compounds. There has been, and still is, considerable debate whether or not ACP is substantially present in skeletal... 

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