High-Efficiency Liquid Chromatographic Separation Utilizing Long Monolithic Silica Capillary Columns

Abstract

Long monolithic silica-C18 capillary columns of 100 μm i.d. were prepared, and the efficiency was examined using reversed-phase HPLC under a pressure of up to 47 MPa. At linear velocities of 1−2 mm/s, 100000−500000 theoretical plates could be generated with a single column (90−440 cm in length) using an acetonitrile−water (80/20) mobile phase with a column dead time (t0) of 5−40 min. It was possible to prepare columns with a minimum plate height of 8.5 ± 0.5 μm and permeability of (1.45 ± 0.09) × 10−13 m2. The chromatographic performance of a long octadecylsilylated monolithic silica capillary column was demonstrated by the high-efficiency separations of aromatic hydrocarbons, benzene derivatives, and a protein digest. The efficiency for a peptide was maintained for an injection of up to 0.5−2 ng. When three 100 μm i.d. columns were connected to form a 1130−1240 cm column system, 1000000 theoretical plates were generated for aromatic hydrocarbons with retention factors of up to 2.4 with a t0 of 150 min. The fact that very high efficiencies were obtained for the retained solutes suggests the practical utility of these long monolithic silica capillary columns