| Research Abstract |
Network structures of monolithic silica columns, namely the homogeneity and domain size, were controlled and optimized in the preparation process utilizing sol-gel reactions. It was possible to generate the performance close to that of ultrahigh pressure liquid chromatography without using high pressure by using conventional instrumentation. The generation of 1,000,000 theoretical plates was achieved under 40-50 MPa using a set of long capillary columns connected in series.
An increase in homogeneity of skeletons and through-pores was achieved by employing higher concentration of silanes in feed and by reactions at lower temperatures than previous methods, accompanied by the decrease in domain size. The resulting monolithic silica capillary columns, the second-generation monolithic silica columns, showed column efficiency of 2-2.5 μm particles under pressure drop equivalent to 5 μm particles.
Highly porous monolithic silica columns having 3.5-4 μm domain sizes showed high permeability equivalent to 8-10 μm particles and column efficiency of ca. 4 μm particles, generating 100,000-500,000 theoretical plates with a 100-450 cm column. Such columns, when connected in series, showed 1,000,000 theoretical plates for well retained solutes with retention factors k=2.4 or smaller, and above 800,000 theoretical plates for late-eluting solutes. The results showed first examples of 1,000,000 theoretical plates for retained solutes.
Stationary phases for hydrophilic interaction liquid chromatography (HILIC) and ion exchange mode were prepared from second-generation monolithic silica columns by reacting functional monomers in the column after derivatization of monolithic silica with methacrylamide functionality as an anchor group, resulting in polar-bonded phases that showed much higher column efficiency than existing particle-packed columns.
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