Evaluation of chromatographic versus electrophoretic behaviour of a series of therapeutical peptide hormones

In this work, models describing the effect of pH on chromatographic and electrophoretic behaviour for a series of polyprotic therapeutic peptide hormones were compared, taking into account the species in solution and the activity coefficients. The usefulness of the proposed equations is twofold, they permit the determination of the acidity constants in water and in the hydroorganic mobile phases used in liquid chromatography (LC) and capillary electrophoresis (CE) and can also be used for the selection of the optimum pH for the separation of mixtures of the modelled compounds. The proposed relationships allow an important reduction of the experimental data needed for the development of new separation methods. The accuracy of the proposed equations is verified by modelling the chromatographic and electrophoretic behaviour of a series of polyprotic therapeutic peptide hormones. By calculating the values of predicted resolutions, selection of the optimum pH to perform LC or CE separations of their mixtures becomes a rapid and simple process.