Experimental Investigation of the Band Broadening Arising from Short-Range Interchannel Heterogeneities in Chromatographic Beds under the Condition of Identical External Porosity

The interesting possibilities offered by micropillar array columns to investigate the relation between bed heterogeneity and band broadening in chromatographic columns are illustrated and investigated. The perfect control over the microscopic bed structure offered by the photolithographic fabrication technique could be used to produce a heterogeneous bed displaying a short-range interchannel heterogeneity and having exactly the same particle size and external porosity as the perfectly ordered bed that was used as the reference system. According to this approach, any observed difference in band broadening could be directly owed to the effect of the bed heterogeneity. Knowing that the only difference between the investigated beds was their degree of heterogeneity, the obtained plate height measurements provided a unique test to distinguish among the abilities to recognize short-range interchannel heterogeneity of the different existing plate height models. Interpreting the data with the classical van Deemter and Knox models, it was found that the increased bed heterogeneity leads not only to an increase in the A-term constant but also to a clear increase in the C-term constant.