Erdemgil F Z, Sanli S, Sanli N, Ozkan G, Barbosa J, Guiteras J, Beltrán J L
Anadolu University, BIBAM, 26470 Eskişehir, Turkey.
Talanta. 2007 Apr 30;72(2):489-96. doi: 10.1016/j.talanta.2006.11.007. Epub 2006 Dec 8.
An accurate estimation of pK(a) values in methanol-water binary mixtures is very important for several separation techniques such as liquid chromatography and capillary electrophoresis that use these solvent mixtures. In this study, the pK(a) values of 11 polyphenolic acids have been determined in methanol-water binary mixtures (10%, 20% and 30% (v/v)) by potentiometry, liquid chromatography (LC) and LC-DAD methodology. The results show a similar trend for the pK(a) values of all the studied compounds, as they increase with increasing concentration of organic modifier, which allows a linear relationship between pK(a) values and mole fraction of methanol to be obtained. The pK(a) values obtained in aqueous medium have been compared with those given in the literature, and also with the values predicted by the SPARC on-line pK(a) calculator. The data obtained have been used to test the feasibility of an estimation of dissociation constants in a methanol-water medium from the relationship between pK(a) values and the organic cosolvent fraction in the mixtures.
对于诸如液相色谱和毛细管电泳等使用甲醇 - 水二元混合物的分离技术而言，准确估算甲醇 - 水二元混合物中的pK(a)值非常重要。在本研究中，通过电位滴定法、液相色谱（LC）和LC - DAD方法测定了11种多酚酸在甲醇 - 水二元混合物（10%、20%和30%（v/v））中的pK(a)值。结果表明，所有研究化合物的pK(a)值呈现相似趋势，随着有机改性剂浓度的增加而增大，这使得能够得到pK(a)值与甲醇摩尔分数之间的线性关系。已将在水介质中获得的pK(a)值与文献中给出的值进行了比较，还与SPARC在线pK(a)计算器预测的值进行了比较。所获得的数据已用于检验根据pK(a)值与混合物中有机共溶剂分数之间的关系估算甲醇 - 水介质中解离常数的可行性。
