Caiali Edvin, David Victor, Aboul-Enein Hassan Y, Moldoveanu Serban C
University of Bucharest, Faculty of Chemistry, Department of Analytical Chemistry, Bucharest, Romania.
National Research Centre, Pharmaceutical and Drug Industries Research Division, Pharmaceutical and Medicinal Chemistry Department, Cairo, Egypt.
J Chromatogr A. 2016 Feb 26;1435:85-91. doi: 10.1016/j.chroma.2016.01.043. Epub 2016 Jan 19.
For a chromatographic column, phase ratio Φ is defined as the ratio between the volume of the stationary phase Vst and the void volume of the column V0, and it is an important parameter characterizing the HPLC process. Although apparently simple, the evaluation of Φ presents difficulties because there is no sharp boundary between the mobile phase and the stationary phase. In addition, the boundary depends not only on the nature of the stationary phase, but also on the composition of the mobile phase. In spite of its importance, phase ratio is seldom reported for commercially available HPLC columns and the data typically provided by the vendors about the columns do not provide key information that would allow the calculation of Φ based on Vst and V0 values. A different procedure for the evaluation of Φ is based on the following formula: log k'j=a log Kow,j+log Φ, where k'j is the retention factor for a compound j that must be a hydrocarbon, Kow,j is the octanol/water partition coefficient, and a is a proportionality constant. Present study describes the experimental evaluation of Φ based on the measurement of k'j for the compounds in the homologous series between benzene and butylbenzene for three C18 columns: Gemini C18, Luna C18 both with 5 μm particles, and a Chromolith Performance RP-18. The evaluation was performed for two mobile phase systems at different proportions of methanol/water and acetonitrile/water. The octanol/water partition coefficients were obtained from the literature. The results obtained in the study provide further support for the new procedure for the evaluation of phase ratio.
对于色谱柱，相比率Φ定义为固定相体积Vst与柱的空体积V0之比，它是表征高效液相色谱过程的一个重要参数。尽管看似简单，但Φ的评估存在困难，因为流动相和固定相之间没有明显的界限。此外，界限不仅取决于固定相的性质，还取决于流动相的组成。尽管相比率很重要，但市售高效液相色谱柱很少报告该参数，供应商通常提供的有关色谱柱的数据并未提供基于Vst和V0值计算Φ所需的关键信息。一种不同的Φ评估方法基于以下公式：log k'j = a log Kow,j + log Φ，其中k'j是化合物j的保留因子，该化合物必须是烃类，Kow,j是正辛醇/水分配系数，a是比例常数。本研究描述了基于对三种C18色谱柱（Gemini C18、Luna C18，均为5μm粒径，以及Chromolith Performance RP - 18）上苯和丁基苯之间同系物中化合物的k'j测量对Φ进行的实验评估。评估是在甲醇/水和乙腈/水不同比例的两种流动相系统中进行的。正辛醇/水分配系数从文献中获取。该研究获得的结果为相比率评估的新方法提供了进一步的支持。
