Departament de Química Analítica, Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, Barcelona, Spain.
J Chromatogr A. 2011 Jul 29;1218(30):4995-5009. doi: 10.1016/j.chroma.2010.12.119. Epub 2011 Jan 6.
The retention of 22 monoprotic acid-base solutes in 12 buffers (pH from 2 to 12) at 3 temperatures (25, 40 and 55°C) and in 3 mobile phase compositions (20, 40 and 60% acetonitrile) was measured. The retention data for each solute, temperature and mobile phase compositions was fitted to pH by means of the common sigmoidal equation and the retention and acid-base parameters were obtained (logk(HA), logk(A) and pK(a)). The dependence of these parameters on temperature (van't Hoff plots), mobile phase composition (ϕ, volume fraction of acetonitrile) and mobile phase polarity (P(m)(N) parameter) was investigated. Linear plots of the parameter values against the reverse of the absolute temperature, on one hand, and ϕ or P(m)(N), in the other hand, were generally obtained. From this analysis we propose 6-parameter equations to relate retention to pH and T at constant mobile phase composition, and to pH and ϕ or P(m)(N) at constant temperature. A general 12 parameter equation is also proposed to relate retention simultaneously to pH, T and ϕ or P(m)(N). The general constancy of some terms of the equations allow to simplify the 12 parameter equation to a 8 parameter equation able to predict retention of the studied solutes. The accuracy of the proposed method provided excellent results with the advantage of modeling the effects of various optimization variables (modifier concentration, mobile phase pH and temperature) using a single equation, based on only eight fitting parameters.
在 3 种温度（25、40 和 55°C）和 3 种流动相组成（20、40 和 60%乙腈）下，测量了 12 种缓冲液（pH 值为 2 至 12）中 22 种单质子酸碱溶质的保留值。使用通用的 S 型曲线方程将每种溶质、温度和流动相组成的保留数据拟合至 pH 值，并获得了保留和酸碱参数（logk(HA)、logk(A)和 pK(a)）。研究了这些参数与温度（范特霍夫图）、流动相组成（ϕ，乙腈的体积分数）和流动相极性（P(m)(N)参数）的关系。一方面，参数值与绝对温度倒数的线性图，另一方面，参数值与 ϕ 或 P(m)(N)的线性图，通常是得到的。从这种分析中，我们提出了 6 参数方程，以在恒定流动相组成的条件下将保留值与 pH 和 T 相关联，在恒定温度的条件下将保留值与 pH 和 ϕ 或 P(m)(N)相关联。还提出了一个通用的 12 参数方程，以同时将保留值与 pH、T 和 ϕ 或 P(m)(N)相关联。方程中一些项的通用性允许将 12 参数方程简化为 8 参数方程，该方程能够预测所研究溶质的保留值。所提出方法的准确性提供了出色的结果，其优点是使用单个方程基于仅 8 个拟合参数来模拟各种优化变量（改性剂浓度、流动相 pH 值和温度）的影响。
