Fundamental Considerations of Packed-Capillary GC, SFC, and LC Using Nonporous Silica Particles

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In this study, nonporous silica (NPS) particles with diameters from 5 to 25 μm were packed into fused silica capillary columns of 250 μm i.d. using a CO 2 slurry packing method. The column efficiency in LC was investigated using least-squares analysis of the experimental data according to the Giddings and van Deemter equations, and the results were compared with those obtained from columns containing porous silica (PS) particles. Less resistance to mass transfer was found for columns packed with NPS particles. For GC and SFC conditions, the van Deemter equation was modified by considering the compressibility of the mobile phase, and the modified equations were used to explain experimental results. The columns packed with NPS particles produced smaller resistance to solute mass transfer and higher optimum mobile phase linear velocities than those containing PS particles under SFC and GC conditions. In GC, it was found that the optimum mobile phase linear velocity increased with increasing particle size. The column permeability was investigated under GC, SFC, and LC conditions by measuring the pressure drop, and it was found that much lower pressure drops were produced along columns packed with NPS particles than with PS particles.