Comparison of the performance of Chromolith Performance RP-18e, 1.8-μm Zorbax Eclipse XDB-C18 and XTerra MS C18, based on modelling approaches

Achievement of the highest separation efficiency and quick delivery of results are key requirements in liquid chromatography for enhancing productivity and reducing analysis cost, especially in the pharmaceutical industry. This work concerns two of the most popular current solutions to get fast separations: the use of a silica-based monolithic column (Chromolith Performance RP-18e) and a small-particle packed column (1.8-μm Zorbax Eclipse XDB-C18, which needs dedicated instruments allowing higher backpressures). Both columns succeeded in the full separation of phenols and β-adrenolytic drugs, which are compounds that interact with residual silanols, giving rise to wider peaks. The results were compared with those obtained with a special column designed to avoid silanol interaction, containing 5 μm particles (XTerra MS C18). Chromolith gave the shortest times at the expense of higher solvent consumption at the high flow rates needed. In contrast to other studies, comprehensive conclusions on the chromatographic performance, in terms of selectivity, peak shape, resolution, and analysis time, are derived from the inspection of the whole experimental domain using retention and peak shape modelling. In the literature, column comparison is usually carried out based on the performance for selected mobile phases (very often a single one), which offers deceiving results.