Improving separation optimization in capillary electrophoresis by using a general quality criterion

In this paper we extend the use of the quality criterion t^' to optimize separations in capillary electrophoresis (CE). The theoretical parameter t' takes into account not only the relative separation between a given pair of compounds but also their separation from the neutral species migrating with the electroosmotic flow (EOF). Furthermore, it can be composed for complex mixtures as a global multicriterium optimization function T', for a rapid, simple and reliable selection of optimized separation conditions by mathematical maximization. Here, we demonstrate the applicability of T' using as a variable the electrophoretic mobility (m_e) for the optimization of pH in the separation of a mixture of amyloid beta (Aβ) peptide fragments. In addition, it is shown the versatility of T' using other variables related to m_e, which do not require experimental measurements. This is the case with ionizable compounds as the Aβ peptide fragments, whose charge-to-mass ratios can be calculated if accurate pK_a values are available in the literature. The excellent performance of T' for Aβ peptide fragments is further validated optimizing the pH for the separation of mixtures of harmala alkaloids (HAlks) and quinolone antibiotics.