[Determination of absolute mobility and dissociation constant of lovastatin using capillary electrophoresis and empirical equation of ion mobility]

作为一种可以预防动脉粥样硬化和冠心病的潜在药物洛伐他汀,其绝对淌度m₀和解离常数pK_a值的测定有助于其性质与应用的研究。在前期相关研究基础上,该文提出了一种基于毛细管区带电泳(CZE)和离子淌度经验公式测定洛伐他汀m₀和pK_a的新方法。首先,根据经验公式由实际淌度(m_act)、有效淌度(m_eff)和m₀之间的关系推导出m₀的计算公式。对于一元酸HA,根据之前m₀的计算公式,以氢离子的浓度为自变量,m_eff的倒数为因变量可得到一条直线。根据这条直线的斜率计算得到pK_a。为了验证该方法的可行性和可靠性,应用该方法测定了巴比妥酸、苯甲酸、苄胺、苯酚、间甲酚等有机酸碱的m₀和pK_a值。同时,对于pH值低于6的缓冲体系,采用反向毛细管电泳技术,测定其pK_a,并将测得的实验结果与理论参考值进行对比,发现两者具有较高的一致性,m₀的标准偏差小于6.0%, pK_a的标准偏差小于6.2%,且由线性回归方程的相关系数(R)可以看出测定pK_a时的线性回归直线拟合度较好,说明该文建立的新方法具有较高的可靠性。最后基于这种CZE与经验公式结合的新方法,采用二甲基亚砜(DMSO)作为电渗流标记物测定了洛伐他汀的m₀和pK_a,得到的值分别为-1.70×10^-8 m²/(V·s)和9.00。该方法适用于酸性和碱性分析物m₀和pK_a等理化参数的测定,在药物分析尤其是新药理化特性研究中具有重要意义。

Dynamic computer simulations of electrophoresis: 2010-2020

The transport of components in liquid media under the influence of an applied electric field can be described with the continuity equation. It represents a nonlinear conservation law that is based upon the balance laws of continuous transport processes and can be solved in time and space numerically. This procedure is referred to as dynamic computer simulation. Since its inception four decades ago, the state of dynamic computer simulation software and its use has progressed significantly. Dynamic models are the most versatile tools to explore the fundamentals of electrokinetic separations and provide insights into the behavior of buffer systems and sample components of all electrophoretic separation methods, including moving boundary electrophoresis, CZE, CGE, ITP, IEF, EKC, ACE, and CEC. This article is a continuation of previous reviews (Electrophoresis 2009, 30, S16–S26 and Electrophoresis 2010, 31, 726–754) and summarizes the progress and achievements made during the 2010 to 2020 time period in which some of the existing dynamic simulators were extended and new simulation packages were developed. This review presents the basics and extensions of the three most used one‐dimensional simulators, provides a survey of new one‐dimensional simulators, outlines an overview of multi‐dimensional models, and mentions models that were briefly reported in the literature. A comprehensive discussion of simulation applications and achievements of the 2010 to 2020 time period is also included.

Determining binding constants for 1:1 and 1:2 inclusion complexes of ester betulin derivatives with (2-hydroxypropyl)-β-cyclodextrin by affinity capillary electrophoresis

The complexation of ester betulin derivatives with (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) was studied by mobility shift affinity CE. Electrophoretic mobility for triangular peaks was calculated using the parameter a₁ of the Haarhoff-Van der Linde function instead of the peak top time. Dependences of the viscosity corrected electrophoretic mobility on HP-β-CD concentration were not described on the basis of only complexes with 1:1 stoichiometry due to the fact that these binding curves did not reach a plateau. However, the dependences were well described taking into account both 1:1 and 1:2 complexes. The presence of higher order equilibria was also revealed by x-reciprocal plots. The values of apparent binding constant logarithm, obtained for the first time, for 1:1 and 1:2 HP-β-CD complexes of betulin 3,28-diphthalate and betulin 3,28-disuccinate with 95% confidence interval limits in brackets are the same within error and are equal to 4.85 (4.73-4.95), 8.56 (7.75-8.82), 4.92 (4.86-4.97), and 8.54 (8.23-8.72) at 25°C, respectively. These values for 1:1 and 1:2 HP-β-CD complexes of betulin 3,28-disulfate at 25°C are 4.61 (4.57-4.64) and 7.11 (6.57-7.34), respectively. The binding constants for betulin 3,28-disulfate agree with the previously obtained results from the separation in the thermostatted capillary segment.