Comparison of the fast gradient performance of new prototype silica monolithic columns and columns packed with fully porous and core–shell particles

The gradient elution performance of narrow-bore 2.3 mm × 50 mm (N733) and wider bore 3.2 mm × 50 mm (N648 and N655) prototype silica monolithic columns was investigated and compared to the performance of commercially available columns packed with sub-2 μm fully porous particles (2.1 mm × 50 mm, 1.7 μm BEH-C18, Waters) and sub-3 μm superficially porous particles (2.1 mm × 50 mm, 2.7 μm Halo-ES-Peptide-C18 (AMT), 1.7 and 2.6 μm Kinetex-C18, Phenomenex). Results show that the two wide monolithic columns show peak capacities similar to the one measured for the Kinetex column. In contrast, the narrow-bore monolithic column delivers a lower performance (−30%) than the BEH, the Halo and the Kinetex columns. This work stresses out the importance of reducing the extra-column band broadening contribution of HPLC instruments when short 2.1 mm I.D. columns are used. The part of the instrument contribution originating downstream the column is important for all compounds; the one originating upstream the column is significant only for weakly retained compounds.