A Semi-Empirical Approach for a Rapid Comprehensive Evaluation of the Electrophoretic Behaviors of Small Molecules in Free-Zone Electrophoresis

A phenomenological model is proposed for the evaluation of relative electrophoretic migration of charged substances present in mixtures and for the rapid pH optimization prior to capillary zone electrophoresis method development. The simple and robust model is based on the Offord model, which takes account of the chemical structure. The effective charge and the molecular mass of the molecule are needed; the charge can easily be calculated from pK_a obtained from known sources or simulated with existing pK-calculation programs. A first example was chosen with the separation of hydroxy-s-triazines to illustrate the applicability of this simple approach for determination of the first buffer-pH conditions prior experimental method optimization when separation of different ions is needed. In a second example, the confirmation of aminialcohols in the CZE method development of unsaturated hexahydro-triazines and oxasolidines.