Detailed kinetic performance analysis of micromachined radially elongated pillar array columns for liquid chromatography

The individual factors that determine the kinetic performance (B- and C-term band broadening and bed permeability K-v) of radially elongated pillar (REP) columns are studied. To this end, columns with REPs having 4 different aspect ratios (AR = 9, 12, 15, 20) were characterized experimentally and by means of numerical simulations. A tortuosity and retention based plate height equation was established, enabling a good global fit for all studied conditions. The B-term plate height contribution appears to decrease with a factor equaling the square of the flow path tortuosity tau. Going from AR= 12 to AR= 20 (tau = 5.7 and tau = 9.0 respectively), this resulted in a shift in plate height expressed in axial coordinates from H-min =0.42 mu m to H-min = 0.25 for non-retained conditions and from H = 0.77 mu m to H = 0.57 mu m for a component with k = 1.0. The obtained parameters were combined to predict optimal time-efficiency combinations for all possible channel lengths. This revealed an efficiency limit of N = 10(7) plates for a non-retained component and N = 7-8 x 10(6) for k=1 for a channel with an AR= 20, corresponding to a channel length of 2.5 m and a void time of 2.4h. (C) 2016 Elsevier B.V. All rights reserved.