Robustness of the chromatographic separation of alprenolol and related substances using a silica-based stationary phase and selective retention of metoprolol and related substances on a porous graphitic carbon stationary phase

In this study the robustness of two different LC methods for quantification of alprenolol and estimation of related substances was compared. In the first LC method a silica-based material, i.e., Hibar LiChrosorb RP-8, was used as the stationary phase and the mobile phase consisted of a counter-ion dissolved in acidic buffer and acetonitrile. The mobile phase in the other method consisted of alkaline methanol and as the stationary phase was porous graphitic carbon, Hypercarb, used. The robustness of the methods were investigated by experimental design and evaluated with multivariate calculations. The porous graphitic carbon system was far more robust than the silica system. The retention order of alprenolol and three related substances were the same, within the experimental design, when using the Hypercarb column. All the tested variables for the silica-based column were shown to have a significant effect on the retention behavior of the solutes. Most alarming is the retention shift of some of the solutes under the tested experimental intervals used. Separations of other closely related amino alcohols on Hypercarb are also presented. Metoprolol and related substances were baseline resolved with high column efficiencies, >60 000 plates/m, using the latest version of Hypercarb. (C) 1998 Elsevier Science B.V.