Octacalcium Phosphate Solubility Product from 4 to 37 °C
Octacalcium Phosphate Solubility Product from 4 to 37 °C
复制标题
DOI：
10.6028/jres.093.153
复制
发表时间：
1988-10-01
影响因子：
--
通讯作者：
Brown WE
中科院分区：
文献类型：
--
作者：
Tung MS;Eidelman N;Sieck B;Brown WE
磷酸八钙(OCP)被证明是牙齿和骨骼矿物质形成和各种病理性钙化的重要中介。在这种矿物形成之前，必须超过它的溶解度积。因此，要基本了解钙化过程，就需要了解其在各种条件下的精确值。建立了适用于测量亚稳态相溶解度的方法，并用于确定OCP在4、4.8、6、18、23.5和37℃时的溶解度积pKsp(OCP)的负对数。该方法包括(1)使用高固液比，10 mg/mL，以最大限度地减少水解的影响，(2)在平衡过程中频繁采样，以检测可能的水解影响，(3)从过饱和和欠饱和平衡，以及(4)在没有和存在含CO2气氛的情况下进行平衡。在4℃、4.8℃、6℃、18℃、23.5℃和37℃时，表观pKSP(OCP)值分别为48.3±0.2、48.3±0.2、48.2、48.3、48.4±0.1和48.7±0.2。5.5%CO2气氛对表观pKSP(OCP)值无显著影响。过饱和与欠饱和接近平衡得到的pKsp(OCP)值基本相同。描述了(1)使用不同的离子模型，(2)OCP水解，(3)平衡常数的差异对表观pKSP(OCP)值的影响，后两者对pKSP(OCP)的差异有很大的贡献。
Octacalcium phosphate (OCP) is proving to be an important intermediary in the formation of tooth and bone mineral and various pathological calcifications. Before this mineral can form, its solubility product must be exceeded. Thus, a knowledge of its precise values under various conditions is required for a basic understanding of calcification processes. The methodology suitable for measuring the solubility of metastable phases was developed and used to determine the negative logarithms of the solubility products of OCP, pKsp(OCP), at 4, 4.8, 6, 18, 23.5, and 37 °C. This methodology includes (1) the use of high solid-to-liquid ratio, 10 mg/mL, to minimize the effects of hydrolysis, (2) frequent sampling during equilibration to detect possible effects of hydrolysis, (3) equilibration from supersaturation and from undersaturation, and (4) equilibration in the absence and presence of a CO2-containing atmosphere. The resulting pKsp(OCP) values are 48.3±0.2, 48.3±0.2, 48.2, 48.3, 48.4±0.1 and 48.7±0.2 at 4, 4.8, 6, 18, 23.5, and 37 °C. A 5.5% CO2 atmosphere did not change the apparent pKsp(OCP) value significantly. The value of pKsp(OCP) obtained by approaching equilibrium from supersaturation was essentially the same as that from undersaturation. The effects of (1) the use of different ionic models, (2) OCP hydrolysis, and (3) differences in equilibrium constants on the apparent pKsp(OCP) values are described; the latter two contribute significantly to the differences in pKsp(OCP).