恒定分压CO_2对羟基磷灰石溶解度的影响

Effect of CO_2 in Constant Pressure on Solubility of Hydroxyapatite

【目的】应用固体滴定技术监测羟基磷灰石(Hydroxyaptite,HA)的溶解平衡过程,观察组织液生理浓度CO2对羟基磷灰石溶解度的影响。【方法】在恒温水浴系统中以HA为固体滴定物。测试液为KCl溶液(0.1 mol/L),并引入恒定分压的CO2(占空气体积比为3.5%±0.1%)。半导体二极管激光为发射光源,散射光源探测器用于监测HA的溶解平衡过程并判断超越溶解平衡点所出现的沉淀(合共17次滴定终点)。同体滴定总量用于代表溶解度等温线上的数据点。【结果】引入恒定分压CO2后测定的HA在KCl溶液中的溶解度高于其在KCl溶液中所得50倍以上。【结论】固体滴定技术利于监测HA的溶解平衡过程。溶液体系中CO2增加HA的溶解度。推测该现象与CO32-形成的复合物密切相关。

[Objective]To study the effect of CO2 in constant pressure on the solubility of hydroxyapatite (HA) using the small-increment solid titration method. [Methods] The solid used was HA. The tested solution was potassium chloride (0.1mol/L) equilibrated with 3.5 %±0.1% CO2 in air. A diode laser served as the light source and the laser-scattering detector was used to monitor the precipitation occurring just after the equilibrium point. Totally 17 end points of the amount of HA added was taken as representing a point on the solubility isotherm. [Results] The solubility isotherm of HA in the tested solution at 37℃ was higher than that in the plain KCl (0.1 mol/L) solution ( 50 times, roughly). [Conclusion] The small-increment solid titration method is applicable for the study of equilibrium of HA. The effect of physiological CO2 was found to increase the solubility of HA and this may be due to the formation of carbonate complexes.