Selection of comparison criteria and experimental conditions to evaluate the kinetic performance of monolithic and packed-bed columns

The present study concerns the problem of finding appropriate experimental conditions and comparison criteria to assess the kinetic performance of LC supports with different sizes or morphologies. A general procedure, based on evaluating each support for its own optimal mobile-phase composition, is proposed. The practical elaboration of the procedure is illustrated using the specific case of a capillary LC separation of a series of polycyclic aromatic test compounds employing silica-monolith capillary columns and capillary columns packed with 6-mu m porous particles. To compare the systems for their ability to yield the fastest critical-pair separation, plate-height measurements are transformed into an effective plate number kinetic plot, i.e., a plot of the extrapolated retention time divided by the square of the extrapolated effective plate number (t(R)/N-eff(2)) versus N-eff. This type of data representation provides a direct and universal basis to compare the kinetic performance of different LC supports and it corrects for differences in retention strength arising from different phase ratios. (c) 2006 Elsevier B.V. All rights reserved.