Abstract

The present work aims to analyze the effect of solution non-ideality on the magnitude of supersaturation of cholesterol (3) for crystallization from its solution in organic solvent (2) using water (1) as antisolvent. Real supersaturation (S) has been computed as the ratio of activities (a₃/a₃*) at the supersaturated (x₃) and saturated (x₃*) mole fractions respectively, by multiplying the ideal solution supersaturation (S_x = x₃/x₃*) with the activity coefficient ratio [γ₃/γ₃*]. The values of [γ₃/γ₃*] are estimated using the Pharma Modified UNIFAC model. The x₃* data have been measured experimentally in aqueous organic-solvent mixtures at different values of x₁ in ethanol at three temperatures (T) in the range of 290.5 to 299.5 K, and in acetone and acetonitrile at 299.5 K. These data have been correlated in terms of x₁ and T separately for computation of S_x, [γ₃/γ₃*], and S. The quantitative impact of solution non-ideality on the sensitivity of S to the variations of x₁, x₃, [x₃/x₃*], T and nature of solvent are investigated computationally. It is observed that [γ₃/γ₃*] is less than 1.0 and is relatively more significant at lower x₁ and higher S_x, though it is almost invariant with T and solvent. The value of S_x at 299.5 K is found higher than S by 15% at S_x = 2 and by 162% at S_x = 10. The results clearly establish that it is necessary to include the solution non-ideality in the estimation of solute supersaturation, as otherwise significant errors may result in computing nucleation and growth rates.

摘要

目前的工作旨在分析溶液非理想性对胆固醇 (3) 过饱和程度的影响，以从其在有机溶剂 (2) 中的溶液中结晶，使用水 (1) 作为反溶剂。实际过饱和度 ( S ) 分别计算为过饱和 ( x ₃ ) 和饱和 ( x _{3 *) 摩尔分数下的活度比 (} a ₃ / a ₃ *)乘以理想溶液过饱和度 ( S _x = x ₃ / x ₃ *) 与活动系数比 [γ ₃ /γ ₃*]。[γ ₃ /γ ₃ *] 的值是使用 Pharma Modified UNIFAC 模型估计的。x ₃ * 数据是在 290.5 至 299.5 K 范围内的三个温度 ( T ) 的乙醇中以及在 299.5 K 的丙酮和乙腈中以不同的x ₁值在水性有机溶剂混合物中进行实验测量的。这些数据具有分别根据x ₁和T相关，用于计算S _x、[γ ₃ /γ ₃ *] 和S。解非理想性对S灵敏度的定量影响对x ₁、x ₃、 [ x ₃ / x ₃ *]、T和溶剂性质的变化进行了计算研究。观察到 [γ ₃ /γ ₃ *] 小于 1.0 并且在较低x ₁和较高S _x时相对更显着，尽管它几乎不受T和溶剂的影响。S _x在 299.5 K的值在S _x = 2 时比S高15%，在S _x时高162%= 10. 结果清楚地表明，有必要在溶质过饱和度的估计中包括解决方案的非理想性，否则可能会导致计算成核和生长速率的重大错误。