Enhanced radial dispersion as a means to gain separation performance in miniaturized liquid chromatography systems

In the current contribution, it is demonstrated that radial elongation of support structures in a chromatographic column has an enormous impact on the axial band broadening occurring in the column. By increasing the lateral dimension of the support structures with respect to their axial dimension, axial band broadening could be reduced up to 5 times. For flat rectangular columns filled with 5 μm axial length support structures and a spacing of 2.5 μm, the minimal (apparent) plate height could be reduced from 2.6 to 0.5 μm under non-retained conditions by increasing the ratio of the lateral over the axial dimension from 1.2 to 15. This increase in performance can be addressed to a decrease in longitudinal dispersion, which was reflected in a reduced B-term by a factor of 25. The footprint of the column is dramatically reduced, ending up with an equivalence of 2 million plates per meter for an aspect ratio of 15. Under retained conditions, a 4 component (Coumarin) separation could be demonstrated requiring 1 mm channel length only.