Another important factor to be considered is that the effective thermal conductivity of core-shell particles is greater than that of fully-porous particles due to the presence of the highly conductive solid core. Thus, the heat generated at higher flow rates can be better dissipated, so avoiding the appearance of thermal gradients, what improves the homogeneity of the migration velocities of the molecules along the column, yielding narrower peaks [18].
3. Theoretical aspects of the chromatographic behavior of core-shell silica particles
Exhaustive and critical evaluations of the models and the equations employed to describe the mass-transfer kinetics of the solutes in core-shell particles have been reported [5], [16], [19] and [20]. The differences among the velocities of the molecules of the same analyte migrating along the column cause the broadening of the chromatographic peak. The different causes accounting for peak broadening are modelled by the classical van Deemter equation [Equation (1) and Fig. 2]. In this model, three different terms (A, B and C) sum their contributions to raise the HETP value (H) – i.e. to decrease the column efficiency: