Aunins J G, Southard M Z, Myers R A, Himmelstein K J, Stella V J
J Pharm Sci. 1985 Dec;74(12):1305-16. doi: 10.1002/jps.2600741212.
The dissolution behavior of three carboxylic acids of variable aqueous solubility but with approximately equal pKa values into aqueous buffered solutions has been studied as a function of pH and of buffer properties. The dissolution from constant-surface-area compressed disks of benzoic acid, 2-naphthoic acid, and indomethacin into solutions of constant ionic strength (mu = 0.5 with potassium chloride) and constant pH (maintained by pH stat) at 25 degrees C using a rotating disk apparatus was evaluated. Models for dissolution of these weak acids into diprotic and triprotic buffering media are developed to predict the flux of the acid as a function of bulk solution pH and the physical and chemical properties of the buffer and acid. The models assume that mass transfer can be represented by a single second order diffusive term and that instantaneous equilibrium between all reactive species exists. Values of flux and pH at the solid-liquid interface are calculated and the fluxes compared to experimentally determined values. Reasonable correlation was found between values predicted by the models and experimental flux values. Major influences on model accuracy are the Ka and physical properties of the buffer.
研究了三种在水中溶解度不同但pKa值近似相等的羧酸在缓冲水溶液中的溶解行为，该行为是pH值和缓冲液性质的函数。在25℃下，使用旋转圆盘装置评估了苯甲酸、2-萘甲酸和吲哚美辛从恒定表面积压缩盘溶解到具有恒定离子强度（μ = 0.5，含氯化钾）和恒定pH值（通过pH计维持）的溶液中的情况。建立了这些弱酸在二元和三元缓冲介质中溶解的模型，以预测酸通量与本体溶液pH值以及缓冲液和酸的物理化学性质之间的函数关系。这些模型假设传质可以用单一的二阶扩散项表示，并且所有反应物种之间存在瞬时平衡。计算了固液界面处的通量和pH值，并将通量与实验测定值进行了比较。模型预测值与实验通量值之间发现了合理的相关性。对模型准确性的主要影响因素是缓冲液的Ka值和物理性质。
