牛骨羟基磷灰石在氯化钾溶液中的溶解行为研究

Solubility Behavior of Bovine-Derived Hydroxyapatite in KCl Solution

目的:应用固体滴定法测定牛骨羟基磷灰石在氯化钾溶液中的溶解度(37℃)并鉴定其溶解-再沉淀物的成分。方法:以牛骨羟基磷灰石为固体滴定物加入0.1mol·L-1氯化钾溶液中,运用二极管激光散射监测系统确定滴定终点。利用滴定终点的固体滴定总量和溶液pH值获取无机牛骨的溶解度等温线。使用X射线衍射仪、X射线能谱仪、傅里叶变换红外光谱仪和透视电镜对溶解-再沉淀物进行鉴定。结果:牛骨羟基磷灰石在pH=3.5～5.0的0.1mol·L-1氯化钾溶液中(37℃)的溶解度分别是合成的羟基磷灰石3～20倍。溶解-再沉淀物为羟基磷灰石,结晶度和钙磷比随溶液pH值降低而降低。讨论:牛骨羟基磷灰石中的CO32-,Mg2+和Na+是影响其溶解度高于羟基磷灰石的重要因素。固体滴定到达滴定终点时仅有微量固体过量,有效避免过量固体对材料溶解度测定的影响。结论:固体滴定法可作为测定磷酸钙类生物材料溶解度的标准方法。牛骨羟基磷灰石的溶解度与固体的钙磷摩尔比以及CO32-、Na+、Mg2+等离子替代密切相关。溶液pH值的改变影响牛骨羟基磷灰石溶解-再沉淀物的结晶度。

Objective:This study was to determine solubility isotherm of bovine-derived hydroxyapatite(BDHA)in KCl solution at 37℃ by solid titration and to identify the equilibrium solid phase.Methods:The solid used was powdered BDHA.Solid titration was performed in 0.1 mol·L-1 aqueous KCl at 37.0℃,using a diode laser and light-scattering detector to identify the end-point.Total added calcium was plotted against final pH to construct the solubility isotherm.The equilibrium compositions were characterized by X-ray diffraction,energy dispersive X-ray spectroscopy,Fourier-transform infrared spectroscopy and transmission electron microscopy.Results:The solubility of BDHA in 0.1mol·L-1 aqueous KCl was higher than that of synthetic hydroxyapatite from pH 3.5 to 5.0 at 37℃ by a factor of 3-20,respectively.HA was the only phase found at equilibrium from pH 3.5 to 5.0.The crystallinity and Ca/P ratio of equilibrium hydroxyapatite decreased slightly with decreasing pH.Discussion:The presence of CO32-,Mg2+ and Na+ may play a critical role in contributing to the higher solubility of BDHA compared with HA.The true end-point of solid titration is only ever exceeded by a very small amount,eliminating or reducing to insignificance interference from excess solid.Conclusions:Solid titration can be used as a standard method for determining the solubility of calcium phosphate biomaterials.The high solubility of BDHA may be due to both the low Ca/P ratio and the presence of CO32-,Na+ and Mg2+.The crystallinity of equilibrium hydroxyapatite is affected by the acidity of the solution.