Departament de Química Analítica, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona, Martí i Franquès 1-11, E-08028 Barcelona, Spain.
J Chromatogr A. 2010 Dec 24;1217(52):8340-5. doi: 10.1016/j.chroma.2010.10.060. Epub 2010 Oct 23.
A fast method for the determination of acidity constants by CZE has been recently developed. This method is based on the use of an internal standard of pK(a) similar to that of the analyte. In this paper we establish the reference pK(a) values of a set of 24 monoprotic neutral acids of varied structure that we propose as internal standards. These compounds cover the most usual working pH range in CZE and facilitate the selection of adequate internal standards for a given determination. The reference pK(a) values of the acids have been established by the own internal standard method, i.e. from the mobility differences between different acids of similar pK(a) in the same pH buffers. The determined pK(a) values have been contrasted to the literature pK(a) values and confirmed by determination of the pK(a) values of some acids of the set by the classical CE method. Some systematic deviations of mobilities have been observed in NaOH buffer in reference to the other used buffers, overcoming the use of NaOH in the classical CE method. However, the deviations affect in a similar degree to the test compounds and internal standards allowing thus, the use of NaOH buffer in the internal standard method. This fact demonstrates the better performance of the internal standard method over the classical method to correct mobility deviations, which together with its fastness makes it an interesting method for the routine determination of accurate pK(a) values of new pharmaceutical drugs and drug precursors.
最近开发了一种通过 CZE 快速测定酸度常数的方法。该方法基于使用与分析物 pKa 相似的内标。本文建立了一组 24 种不同结构的单质子中性酸的参考 pKa 值，这些酸被提议作为内标。这些化合物涵盖了 CZE 中最常用的工作 pH 范围，并为给定的测定选择合适的内标提供了便利。酸的参考 pKa 值是通过自身的内标法确定的，即在相同 pH 缓冲液中不同 pKa 相近的酸之间的迁移率差异。测定的 pKa 值与文献中的 pKa 值进行了对比，并通过经典 CE 法测定了该组中一些酸的 pKa 值进行了验证。与其他使用的缓冲液相比，在 NaOH 缓冲液中观察到迁移率存在一些系统偏差，克服了在经典 CE 法中使用 NaOH。然而，这些偏差对测试化合物和内标物的影响程度相似，因此允许在内部标准方法中使用 NaOH 缓冲液。这一事实表明，与经典方法相比，内标法在修正迁移率偏差方面具有更好的性能，其快速性使其成为一种有趣的方法，可用于常规测定新药物和药物前体的准确 pKa 值。
