Characterization of new types of stationary phases for fast liquid chromatographic applications

The performance of a narrow bore silica based monolith column (5 cm × 2 mm) was compared to 5 cm long narrow bore (internal diameter ≤ 2.1 mm) columns, packed with shell particles (2.7 μm) and totally porous sub-2 μm particles (1.5 μm, 1.7 μm and 1.9 μm) in gradient and isocratic elution separations of steroids. The highest peak capacity could be achieved with the column packed with 1.5 μm totally porous particles. The columns packed with porous 1.7 μm and shell 2.7 μm particles showed very similar capacity. The monolith column provided the lowest capacity during gradient elution. The plate height (HETP) of the 2.7 μm Ascentis Express column was very similar to the HETP obtained with 1.5 μm and 1.7 μm totally porous particles. The Chromolith monolithic column displayed an efficiency that is comparable to that of columns packed with spherical particles having their diameter between 3 μm and 4 μm. A kinetic plot analysis is presented to compare the theoretical analysis speed of different separation media. At 200 bar, the monolith column provided the highest performance when the required plate number was higher than 5000 (N > 5000), however the efficiency drifted off faster in the range of N < 5000 than in the case of packed columns. If the possibility of maximum performance was utilized (1000 bar for sub-2 μm particles, 600 bar for shell particles and 200 bar for monolith column) the monolith column would provide the poorest efficiency, while the column, packed with 1.5 μm particles offered the shortest impedance time.