Application of a mixture design technique to the simultaneous optimization of analysis time and resolution in reversed-phase ion-pair liquid chromatography using a minimal resolution plot

Abstract Based on a simple model, the influence of the experimental parameters on solvent strength and selectivity in reversed-phase ion-pair high-performance liquid chromatography is discussed. For optimization of the separation, a mixture design is proposed in which the pH, the content of organic modifier and the concentration of the pairing ion in the mobile phase vary. This design was applied to the separation of two mixtures of four pharmaceutically important amines (water-soluble vitamins and local anaesthetics). By a suitable choice of the three (pseudo) components, which are mixed to compose the mobile phase, it is possible to optimize the resolution of the worst separated pair of peaks and to locate in the optimal region the chromatogram with the minimal analysis time.