Hydroxyl apatite preparation

Smith, G. J., McFarland, R. D., Reisner, H. M., and Hudson, G. S. (1984). Lymphoblastoid cell-produced immunoglobulins Preparative purification from culture medium by hydroxyl-apatite chromatography. Anal. Biochem. 141, 432-436. 

Bukovsky, J., and Kennet, R. (1987). Simple and Rapid Purification of Monoclonal Antibodies from Cell Culture Supernatants and Ascites Fluids by Hydroxyl Apatite Chromatography on Analytical and Preparative Scales, Hybridoma 6 219-228. 

The surface ions of the apatite crystals are therefore readily exchanged with ions of the medium capable of replacing calcium e.g., magnesium), phosphate e.g., carbonate or citrate), or the hydroxyl e.g., fluorine). As we shall see, the surface reaction assumes particular importance in the process of mineralization, and some investigators claim that the lack of stoichiometry in apatite preparations can be entirely explained by such surface reactions. 

The methods of synthesis of fluorapatite have been widely dis cussed (J ). It is for example possible to obtain fluorapatite by substituting the hydroxyl ion for the fluoride ion, either in a-queous solution at room temperature, or through a solid state reaction at 800°C. It can also be prepared by the action of 6-tricalcium phosphate on calcium fluoride at about 800°C. Its solubility and thermal stability have already been established. While much is known about fluorapatite, many questions still exist concerning the mechanism of their formation, their composition and the structure of some of them. Two of these problems are dealt with here. First, we discuss the formation mechanism of fluorapatite by a solid state reaction between calcium fluoride and apa-titic tricalcium phosphate. Then we present the preparation and the structure of a carbonated apatite rich in fluoride ions. 

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