Solubility product of OH-carbonated hydroxyapatite

✍ Scribed by Ito, Atsuo ;Maekawa, Kentaro ;Tsutsumi, Sadao ;Ikazaki, Fumikazu ;Tateishi, Tetsuya

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 173 KB
• Volume: 36
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/(sici)1097-4636(19970915)36:4<522::aid-jbm10>3.0.co;2-c

✦ Synopsis

Information on the solubility of OH-carbonated hydroxyapatite, Ca10(PO4)6(CO3)x(OH)2-2x, previously has not been available. In the present study the solubility product (Ksp) of OH-carbonated hydroxyapatite was measured in a 0.1 M acetic acid and sodium acetate buffer solution in a pH range of 4.0-5.8 at a CO2 partial pressure of 10(-3.52) atm. The equilibrium solubility increased with the increase of carbonate content. The Ksp values decreased with the decrease of pH. For example, Ksps were 10(-119), 10(-123), and 10(-130) for pure hydroxyapatite at pH 4.9, 4.5, and 4.1, respectively. The decrease of Ksp was not accounted for by calcium-carbonate complexation. Ksp measured at isoelectric points (L) was expressed as pL = 118.65 - 0.47316 x (CO2 wt%)2.4176. From this formula, the L values were calculated for pure and fully carbonated hydroxyapatite as 10(-118.7) and 10(102.8), respectively. The L value for pure hydroxyapatite agreed with values measured under carbonate-free conditions. Therefore, the L values were regarded as the Ksp for OH-carbonated hydroxyapatite excluding errors arising from carbonate contamination in the solution.