Performance of octadecylsilylated monolithic silica capillary columns of 530 μm inner diameter in HPLC

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Abstract
Monolithic silica capillary columns were successfully prepared in a fused silica capillary of 530 μm inner diameter and evaluated in HPLC after octadecylsilylation (ODS). Their efficiency and permeability were compared with those of columns packed with 5‐μm and 3‐μm ODS‐silica particles. The monolithic silica columns having different domain sizes (combined size of through‐pore and skeleton) showed 2.5–4.0‐times higher permeability (K = 5.2–8.4×10–14 m2) than capillary columns packed with 3‐mm particles, while giving similar column efficiency. The monolithic silica capillary columns gave a plate height of about 11–13 μm, or 11 200–13 400 theoretical plates/150 mm column length, in 80% methanol at a linear mobile phase velocity of 1.0 mm/s. The monolithic column having a smaller domain size showed higher column efficiency and higher pressure drop, although the monolithic column with a larger domain size showed better overall column performance, or smaller separation impedance (E value). The larger‐diameter (530 μm id) monolithic silica capillary column afforded a good peak shape in gradient elution of proteins at a flow rate of up to 100 μL/min and an injection volume of up to 10 μL.